Cardiovascular autonomic nervous function in children conceived by assisted reproductive technology with frozen or fresh embryo transfer.

As a result of epigenetic changes, children conceived by assisted reproduction may be at risk of premature cardiovascular aging with notably increased blood pressures. Their cardiovascular autonomic nervous function is unknown. Therefore, this study investigated the cardiovascular autonomic nervous function in 8-12-yr-old children (51% girls) conceived naturally (n = 33) or by assisted reproduction with frozen (n = 34) or fresh (n = 38) embryo transfer by evaluating heart rate variability, during rest; from provocation maneuvers; and from baroreflex function. Heart rate and blood pressure response to provocation maneuvers and baroreflex function were comparable between children conceived naturally or by assisted reproduction. The mean RR-interval and high-frequency component of heart rate variability were lower in children conceived by assisted reproduction than in children conceived naturally. Children conceived by fresh embryo transfer had ∼17% lower heart rate-corrected standard deviation of normal-to-normal R-R intervals; ∼22% lower heart rate-corrected square root of the mean of the squared difference between successive R-R intervals; and ∼37% higher low-frequency/high-frequency ratio than naturally conceived children. Children conceived by assisted reproduction still had lower heart rate variability and vagal modulation than naturally conceived children after adjustment for confounders. Thus, these results raise the possibility of sympathetic predominance in children conceived by assisted reproduction. Therefore, it is important to reproduce these results in larger and older cohorts as sympathetic predominance relates with cardiovascular and metabolic diseases.NEW & NOTEWORTHY We observed that children conceived by assisted reproductive technology (both frozen and fresh embryo transfer) had lowered heart rate variability during rest as compared with children conceived naturally. During physiological stress maneuvers, however, the cardiovascular autonomic nervous regulation was comparable between children conceived by assisted reproductive technologies and naturally. Our findings highlight the potential that lowered heart rate variability during rest in children conceived by assisted reproductive technologies may precede premature hypertension.

Double versus single stimulation in young low prognosis patients followed by a fresh embryo transfer: a randomized controlled trial (DUOSTIM-fresh).

STUDY QUESTION: Does double stimulation, followed by a fresh embryo transfer (DUOSTIM fresh) give a higher number of good-quality blastocysts as compared with a single stimulation in young low prognosis patients? SUMMARY ANSWER: Compared to single stimulation, DUOSTIM fresh leads to a significantly higher number of good quality blastocysts, without hindering fresh embryo transfer outcomes. WHAT IS KNOWN ALREADY: DUOSTIM (ovarian stimulation both in the follicular and luteal phase of the same cycle) is an innovative strategy to retrieve a higher number of oocytes in a shorter time frame, thus it is particularly appealing for poor ovarian responders. Three current limitations of dual stimulation are: (i) it is unclear whether outcomes of the second (luteal) wave result from the second stimulation, or a carry-over effect from previous follicular stimulation; (ii) the desynchronization between endometrium and ovaries and, (iii) lack of robust evidence. No previous studies explored DUOSTIM starting from the luteal phase, and with a fresh embryo transfer (DUOSTIM fresh). STUDY DESIGN, SIZE, DURATION: This study is a randomized, controlled, single-center, superiority clinical trial comparing two different ovarian stimulation protocols: a double stimulation cycle versus a single stimulation cycle followed by fresh embryo transfer. The primary outcome was the number of good quality blastocysts obtained, while secondary outcomes included results from fresh embryo transfer (clinical pregnancy, miscarriage). A total of 120 women were enrolled in this study between October 2020 and October 2022, with a 1:1 allocation. PARTICIPANTS/MATERIALS, SETTING, METHODS: Only young (<40 years old) low prognosis (anti-Müllerian hormone <1.2 ng/ml) patients were recruited in the Reproductive Medicine Department of Dexeus University Hospital. In the investigational group, DUOSTIM fresh, the first stimulation was initiated in the luteal phase (Day 18-21 cycle) followed by a second stimulation 5 days post first oocyte retrieval, initiated in the follicular phase and a fresh embryo transfer of the best blastocyst generated (first or second cycle). The control group performed a follicular phase single stimulation cycle with a fresh embryo transfer. MAIN RESULTS AND THE ROLE OF CHANCE: Overall, 107 patients were analyzed, 53 in the investigational (DUOSTIM fresh) and 54 in the control arm (single stimulation). DUOSTIM fresh resulted in a significantly higher number of good quality blastocysts as compared to single stimulation (difference of mean 0.81, 95% CI 0.12-1.49). The mean percentage of cycles with embryo transfer was comparable (62.3% and 51.9%, respectively for double versus single stimulation). No significant differences were found for clinical outcomes following fresh embryo transfer with an ongoing pregnancy rate of 24.5% for DUOSTIM fresh versus 22.2%, for conventional IVF. Of interest comparisons between different stimulation cycles (A: luteal-phase DUOSTIM fresh, B: follicular-phase DUOSTIM fresh, and C: single stimulation) did not demonstrate any significant difference in terms of ovarian response with the mean (SD) number of mature oocytes being (A: 3.3 (2.9), B: 3.4 (3.4), and C: 3.5 (2.9), respectively). LIMITATIONS, REASONS FOR CAUTION: Study sample size was calculated to detect differences on the mean number of good quality blastocysts. Therefore, results for secondary outcomes (embryo transfer rates and clinical pregnancy rates) should be interpreted with caution as exploratory findings that deserve future investigations. WIDER IMPLICATIONS OF THE FINDINGS: Although DUOSTIM fresh results in a higher number of blastocysts as compared with a single stimulation in young low prognosis patients, the decision of performing dual stim should be evaluated with caution, considering that whether this may improve embryo transfers rate and pregnancy outcomes is still unclear. Results on cumulative-live-birth-rate are warranted. STUDY FUNDING/COMPETING INTEREST(S): The study was an investigator-initiated study supported by an unrestricted grant by Organon. N.P.P. has received grants from Merck Serono, Organon, Ferring Pharmaceutical, Theramex, and Besins Healthcare. N.P.P. has received consulting fees from Merck Serono, Organon, Besins Healthcare, and IBSA. N.P.P. has received honoraria for lectures from Merck Serono, Organon, Theramex, Roche Diagnostics, IBSA, Besins Healthcare, and Ferring. A.R. has received Research grants, honoraria for lectures from Merck Serono, MSD/Organon, Ferring Pharmaceuticals, Besins International, IBSA, Guerbet. The other authors declare that there is no conflict of interest to disclose with respect to the content of this article. TRIAL REGISTRATIO NUMBER: NCT04446845. TRIAL REGISTRATION DATE: 25 June 2020. DATE OF FIRST PATIENT'S ENROLMENT: 30 October 2020.

Age-related increase in live-birth rates of first frozen thaw embryo versus first fresh transfer in initial assisted reproductive technology cycles without PGT.

BACKGROUND: The landscape of assisted reproductive technology (ART) has seen a significant shift towards frozen-thawed embryo transfers (FET) over fresh transfers, driven by technological advancements and clinical considerations. This study aimed to compare live birth outcomes between primary FET and fresh transfers, focusing on cycles without preimplantation genetic testing (PGT), using United States national data from the SART CORS database spanning from 2014 to 2020. METHODS: We performed a retrospective cohort study of autologous first ART cycles without PGT comparing primary embryo transfer (frozen thaw vs. fresh) success rates from the 2014-2020 SARTCORS database. Live-birth rates (LBR) and cumulative live-birth rates (CLBR) were compared between first FET versus first fresh embryo transfer from an index retrieval. Multivariate logistic regression (MLR) determined association between live birth outcomes and method of transfer. In a subsequent sub-analysis, we compared these two embryo transfer methods among patients with either diminished ovarian reserve (DOR) or male factor infertility. RESULTS: 228,171 first ART cycles resulted in primary embryo transfer. 62,100 initial FETs and 166,071 fresh transfers were compared. Initial FETs demonstrated higher LBR and CLBR compared to fresh transfers (LBR 48.3% vs. 39.8%, p < 0.001; CLBR 74.0% vs. 60.0%, p < 0.0001). MLR indicated greater chances of live birth with FET across all age groups, with adjusted odds ratio (aOR) of live-birth incrementally increasing with advancing age groups. For DOR cycles, LBR and CLBR were significantly higher for FET compared to fresh (33.9% vs. 26.0%, p < 0.001, 44.5% vs. 37.6%, p < 0.0001), respectively. MF cycles also demonstrated higher LBR and CLBR with FET (52.3% vs. 44.2%, p < 0.001, 81.2% vs. 68.9%, p < 0.0001), respectively. MLR demonstrated that in DOR cycles, initial FET was associated with greater chance of live birth in age groups ≥ 35yo (p < 0.01), with aOR of live birth increasingly considerably for those > 42yo (aOR 2.63, p < 0.0001). CONCLUSIONS: Overall LBR and CLBR were greater for first FET than fresh transfers with incremental increases in odds of live birth with advancing age, suggesting the presence of a more favorable age-related change in endometrial receptivity present in frozen-thawed cycles. For both DOR and MF cycles, LBR and CLBR after primary transfer were greater for first FET than fresh. However, this was particularly evident in older ages for DOR cycles. This suggests that supraphysiologic stimulation in older DOR cycles may be detrimental to endometrial receptivity, which is in part corrected for in FET cycles.

Competent blastocyst and receptivity endometrium improved clinical pregnancy in fresh embryo transfer cycles: a retrospective cohort study.

BACKGROUND: Embryo quality is usually regarded as a key predictor of successful implantation and clinical pregnancy potential. The identification of embryos that have the capacity to implant and result in a healthy pregnancy is a crucial part of in vitro fertilization (IVF). Usually, morphologically high-quality embryos are chosen for embryo transfer in IVF treatment. The aim of this study was to assess the association between the available blastocyst formation rate and the clinical pregnancy outcome following the first fresh embryo transfer cycle and provide systematic individual treatment to adjust endometrial receptivity for the next transfer cycle. METHODS: This retrospective, single-center study included 512 fresh embryo transfers conducted between 11/2019 and 08/2021, which consisted of 385 cleavage-stage (Day 3) and 127 blastocyst-stage (Day 5) embryo transfers. The two groups were divided into a clinical pregnancy group and a nonclinical pregnancy group for comparison. The association between the available blastocyst formation rate and the clinical pregnancy rate in the Day 3 and Day 5 transfer groups were considered. RESULTS: In the Day 3 group, there were 275 clinical pregnancies, and the clinical pregnancy rate was 71.43%. Although the two pronuclei (2PN) oocyte rate and available embryo rate at Day 3 were significantly higher in the clinical pregnancy group than the nonclinical pregnancy group (P < 0.05), the blastocyst formation rate and the available blastocyst formation rate were not significantly different between the clinical pregnancy group and the nonclinical pregnancy group (P > 0.05). In the Day 5 group, there were 81 clinical pregnancies, and the clinical pregnancy rate was 63.78%. No baseline characteristics showed any obvious differences between the clinical pregnancy group and nonclinical pregnancy group (P > 0.05). The blastocyst formation rate in the nonclinical pregnancy group was higher than that in the clinical pregnancy group, but the difference was not statistically significant (81.06% vs. 77.03%, P = 0.083). Interestingly, the available blastocyst formation rate and the Day 5 available blastocyst formation rate were significantly higher in the nonclinical pregnancy group than the clinical pregnancy group (66.19% vs. 60.79%, P = 0.014; 54.58% vs. 46.98%, P = 0.007). CONCLUSIONS: In fresh cycles, the available blastocyst formation rate was not associated with the clinical pregnancy outcome for Day 3 embryo transfers, and the available blastocyst formation rate was not positively correlated with the clinical pregnancy outcome for Day 5 embryo transfers.

Obstetrical and Neonatal Outcomes of in vitro Fertilization Twins after Fresh Embryo Transfer versus Frozen-Thawed Embryo Transfer.

OBJECTIVES: The limited data regarding obstetrical outcomes in multiple pregnancies following both fresh embryo transfer and frozen-thawed embryo transfer (FET), along with the association between multiple pregnancies and increased pregnancy complications compared to singleton pregnancies, highlight the need for research on this topic. Therefore, this study aimed to compare obstetrical and neonatal outcomes of twin pregnancies after fresh embryo transfer versus FET. DESIGN: This was a retrospective single-center study. PARTICIPANTS: There were in vitro fertilization (IVF) dichorionic twin pregnancies ≥23 weeks of gestation during 2010-2022. SETTING: This retrospective study was based on data recorded at Galilee Medical Center, a tertiary-care university-affiliated hospital, Israel. METHODS: We conducted a comparative analysis of obstetrical and neonatal outcomes between IVF dichorionic twin pregnancies after fresh embryo transfer and those after FET. This analysis included variables such as gestational age at delivery, birthweight, preterm birth rates, low birthweight rates, neonatal intensive care unit admissions, and complications related to prematurity. RESULTS: The study included 389 IVF twin pregnancies: 253 after fresh embryo transfer and 136 after FET. Following fresh embryo transfer compared to FET, the mean gestational age at delivery was earlier (34 + 6 vs. 35 + 5 weeks, p = 0.001) and the rate of preterm birth (<37 weeks) was higher (70.4% vs. 53.7%, p = 0.001). This difference in gestational age at delivery remained significant after adjustment for maternal age, parity, and BMI (OR = 2.11, 95% CI: 2.11-3.27, p = 0.001). Similarly, the difference in preterm birth rates remained significant after adjustment of the same variables (p = 0.001). For the fresh embryo transfer compared to the FET group, the mean birthweight was lower (2,179.72 vs. 2,353.35 g, p = 0.003); and low birthweight and very low birthweight rates were higher (71.2% vs. 56.3%, p < 0.001 and 13.5% vs. 6.7%, p = 0.004, respectively). For the fresh embryo transfer compared to the FET group, the proportions were higher of neonates admitted to the neonatal intensive care unit (23.3% vs. 16.0%, p = 0.019), of neonates with respiratory distress syndrome (10.5% vs. 5.9%, p = 0.045) and those needing phototherapy (23.3% vs. 16.0%, p = 0.019). LIMITATIONS: Limitations of the study include its retrospective nature. Furthermore, we were unable to adjust for some confounders, such as the number of eggs retrieved, the number of embryos transferred, and methods for ovarian stimulation or preparation of the endometrium for embryo transfer. CONCLUSIONS: Obstetrical and neonatal outcomes of twin pregnancies were worse after fresh embryo transfer than after FET. The findings support favorable fetal outcomes after FET and support the current trend of shifting from fresh embryo transfer to FET. Prospective studies are needed to support our results.

High estradiol levels in fresh embryo transfer cycles are not associated with detrimental impact on birth outcomes.

PURPOSE: There is an unclear relationship between estradiol levels and fresh embryo transfer (ET) outcomes. We determined the relationship between estradiol on the day of trigger, in fresh ET cycles without premature progesterone elevation, and good birth outcomes (GBO). METHODS: We identified autologous fresh ET cycles from 2015 to 2021 at multiple clinics in the USA. Patients with recurrent pregnancy loss, uterine factor, and elevated progesterone on the day of trigger (progesterone > 2 ng/mL or 3-day area under the curve > 4.5 ng/mL) were excluded. The primary outcome was GBO (singleton, term, live birth with appropriate weight). Log-binomial generalized estimating equations determined the likelihood of outcomes. RESULTS: Of 17,608 fresh ET cycles, 5025 (29%) yielded GBO. Cycles with estradiol ≥ 4000 pg/mL had a greater likelihood of GBO compared to cycles < 1000 pg/mL (aRR = 1.32, 95% CI 1.13-1.54). Pairwise comparisons of estradiol between < 1000 pg/mL versus 1000-1999 pg/mL and 1000-1999 pg/mL versus 2000-2999 pg/mL revealed a higher likelihood of GBO with higher estradiol (aRR 0.83, 95% CI 0.73-0.95; aRR 0.91, 95% CI 0.85-0.97, respectively). Comparisons amongst more elevated estradiol levels revealed that the likelihood of GBO remained similar between groups (2000-2999 pg/mL versus 3000-3999 pg/mL, aRR 1.04, 95% CI 0.97-1.11; 3000-3999 pg/mL versus ≥ 4000 pg/mL, aRR 0.96, 95% CI 0.9-1.04). CONCLUSION: In fresh ET cycles, higher estradiol levels were associated with an increased prevalence of GBO until estradiol 2000-2999 pg/mL, thereafter plateauing. In fresh ET candidates, elevated estradiol levels should not preclude eligibility though premature progesterone rise, and risk of ovarian hyperstimulation syndrome must still be considered.

Impact of mildly evaluated thyroid-stimulating hormone levels on in vitro fertilization or intracytoplasmic sperm injection outcomes in women with the first fresh embryo transfer: a large study from China.

PURPOSE: This study aimed to investigate the association between mild elevation of thyroid-stimulating hormone (TSH) levels and pregnancy outcomes of in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatments in women with the first fresh embryo transfer. METHODS: Large single-center retrospective cohort study of 15,728 patients from January 2018 to December 2022 were enrolled in the analyses. Clinical pregnancy rates, live birth rates, miscarriage rates, and ectopic pregnancy rates were compared between the TSH levels < 2.5 mIU/L group (N = 10,932) and TSH levels ≥ 2.5 mIU/L group (N = 4796). Subgroup analysis was performed for patients with TSH levels ≥ 2.5 mIU/L, dividing them into the thyroid peroxidase antibody (TPO)-negative group (N = 4524) and the TPO-positive group (N = 272). RESULTS: There were no significant differences in the aforementioned pregnancy outcomes between the TSH levels < 2.5 mIU/L group and TSH levels ≥ 2.5 mIU/L group. Similarly, no significant differences were observed in the pregnancy outcomes between the TPO-negative group and the TPO-positive group. CONCLUSION: Mildly elevated pre-conception TSH levels in thyroid-normal infertile patients did not have an impact on pregnancy outcomes of IVF/ICSI treatments.

Clinical outcomes of fresh and frozen embryos transfer after in vitro fertilization in spouses of patients with severely low sperm concentration and motility. / å› é å¶é‡åº¦å°‘å¼±ç²¾å­ç—‡ä¸å­•æ‚£è€ ä½“å¤–å—ç²¾åŽç§»æ¤æ–°é²œèƒšèƒŽä¸Žå†·å†»èƒšèƒŽä¸´åºŠç»“å±€æ¯”è¾ƒ.

OBJECTIVES: To compare the pregnancy and neonatal outcomes of in vitro fertilization-embryo transfer (IVF-ET) with fresh or frozen embryos in spouses of patients with severely low sperm concentration and motility. METHODS: A total of 2300 patients whose spouses have severely low sperm concentration and motility underwent IVT-ET in the Reproduction Medicine Center, Sir Run Run Shaw Hospital from April 2018 to April 2022. After applying the propensity score matching (PSM), 473 fresh embryo transferred cycles and 473 frozen embryo transferred cycles were selected for the study, and the pregnancy and neonatal outcomes were compared between the two groups. RESULTS: There were no significant differences in pregnancy outcomes and neonatal outcomes between fresh and frozen embryo groups (all P>0.05). In the stratification analysis, the number of retrieved oocytes in the fresh good-quality embryo transfer group was significantly increased compared with the fresh poor-quality embryo group (P<0.05), but the very early pregnancy loss rates were similar between the two groups (P>0.05), while the rate in fresh good-quality embryo transfer group was significantly higher than that in the frozen good-quality embryo transfer group (P<0.05). Among different age groups of women, the number of retrieved oocytes and the level of estrogen in the fresh embryo transfer group was significantly higher in the 20 to <30 years old group than that in the 30 to <35 years old group (both P<0.05), but the clinical pregnancy rate was lower in the 20 to <30 years old group than that in the 30 to <35 years old group (P>0.05). Additionally, the very early pregnancy loss was significantly increased in the fresh embryo group compared with the frozen embryo group in the 20 to <30 years age group (P<0.05). CONCLUSIONS: There were no significant differences in pregnancy and neonatal outcomes between fresh and frozen embryo transfer in spouses of patients with severely low sperm concentration and motility undergoing IVF-ET. Due to the shorter transfer times, less embryo freezing damage and reduced costs, fresh embryo transfer can be considered as the first choice. However, it is not necessary to pursue fresh embryo transfer if maternal oestrogen levels are too high and there is a tendency of overstimulation.

Oral micronized progesterone versus vaginal progesterone for luteal phase support in fresh embryo transfer cycles: a multicenter, randomized, non-inferiority trial.

STUDY QUESTION: Does oral micronized progesterone result in a non-inferior ongoing pregnancy rate compared to vaginal progesterone gel as luteal phase support (LPS) in fresh embryo transfer cycles? SUMMARY ANSWER: The ongoing pregnancy rate in the group administered oral micronized progesterone 400 mg per day was non-inferior to that in the group administered vaginal progesterone gel 90 mg per day. WHAT IS KNOWN ALREADY: LPS is an integrated component of fresh IVF, for which an optimal treatment regimen is still lacking. The high cost and administration route of the commonly used vaginal progesterone make it less acceptable than oral micronized progesterone; however, the efficacy of oral micronized progesterone is unclear owing to concerns regarding its low bioavailability after the hepatic first pass. STUDY DESIGN, SIZE, DURATION: This non-inferiority randomized trial was conducted in eight academic fertility centers in China from November 2018 to November 2019. The follow-up was completed in April 2021. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 1310 infertile women who underwent their first or second IVF cycles were enrolled. On the day of hCG administration, the patients were randomly assigned to one of three groups for LPS: oral micronized progesterone 400 mg/day (n = 430), oral micronized progesterone 600 mg/day (n = 440) or vaginal progesterone 90 mg/day (n = 440). LPS was started on the day of oocyte retrieval and continued till 11-12 weeks of gestation. The primary outcome was the rate of ongoing pregnancy. MAIN RESULTS AND THE ROLE OF CHANCE: In the intention-to-treat analysis, the rate of ongoing pregnancy in the oral micronized progesterone 400 mg/day group was non-inferior to that of the vaginal progesterone gel group [35.3% versus 38.0%, absolute difference (AD): -2.6%; 95% CI: -9.0% to 3.8%, P-value for non-inferiority test: 0.010]. There was insufficient evidence to support the non-inferiority in the rate of ongoing pregnancy between the oral micronized progesterone 600 mg/day group and the vaginal progesterone gel group (31.6% versus 38.0%, AD: -6.4%; 95% CI: -12.6% to -0.1%, P-value for non-inferiority test: 0.130). In addition, we did not observe a statistically significant difference in the rate of live births between the groups. LIMITATIONS, REASONS FOR CAUTION: The primary outcome of our trial was the ongoing pregnancy rate; however, the live birth rate may be of greater clinical interest. Although the results did not show a difference in the rate of live births, they should be confirmed by further trials with larger sample sizes. In addition, in this study, final oocyte maturation was triggered by hCG, and the findings may not be extrapolatable to cycles with gonadotropin-releasing hormone agonist triggers. WIDER IMPLICATIONS OF THE FINDINGS: Oral micronized progesterone 400 mg/day may be an alternative to vaginal progesterone gel in patients reluctant to accept the vaginal route of administration. However, whether a higher dose of oral micronized progesterone is associated with a poorer pregnancy rate or a higher rate of preterm delivery warrants further investigation. STUDY FUNDING/COMPETING INTEREST(S): This research was supported by a grant from the National Natural Science Foundation of China (82071718). None of the authors have any conflicts of interest to declare. TRIAL REGISTRATION NUMBER: This trial was registered at the Chinese Clinical Trial Registry (http://www.chictr.org.cn/) with the number ChiCTR1800015958. TRIAL REGISTRATION DATE: May 2018. DATE OF FIRST PATIENT'S ENROLMENT: November 2018.

A drop in serum progesterone from oocyte pick-up +3 days to +5 days in fresh blastocyst transfer, using hCG-trigger and standard luteal support, is associated with lower ongoing pregnancy rates.

STUDY QUESTION: Do early- and mid-luteal serum progesterone (P4) levels impact ongoing pregnancy rates (OPRs) in fresh blastocyst transfer cycles using standard luteal phase support (LPS)? SUMMARY ANSWER: A drop in serum P4 level from oocyte pick-up (OPU) + 3 days to OPU + 5 days (negative ΔP4) is associated with a ∼2-fold decrease in OPRs. WHAT IS KNOWN ALREADY: In fresh embryo transfer cycles, significant inter-individual variation occurs in serum P4 levels during the luteal phase, possibly due to differences in endogenous P4 production after hCG trigger and/or differences in bioavailability of exogenously administered progesterone (P) via different routes. Although exogenous P may alleviate this drop in serum P4 in fresh transfer cycles, there is a paucity of data exploring the possible impact on reproductive outcomes of a reduction in serum P4 levels. STUDY DESIGN, SIZE, DURATION: Using a prospective cohort study design, following the initial enrollment of 558 consecutive patients, 340 fulfilled the inclusion and exclusion criteria and were included in the final analysis. The inclusion criteria were: (i) female age ≤40 years, (ii) BMI ≤35 kg/m2, (iii) retrieval of ≥3 oocytes irrespective of ovarian reserve, (iv) the use of a GnRH-agonist or GnRH-antagonist protocol with recombinant hCG triggering (6500 IU), (v) standard LPS and (vi) fresh blastocyst transfer. The exclusion criteria were: (i) triggering with GnRH-agonist or GnRH-agonist plus recombinant hCG (dual trigger), (ii) circulating P4 >1.5 ng/ml on the day of trigger and (iii) cleavage stage embryo transfer. Each patient was included only once. The primary outcome was ongoing pregnancy (OP), as defined by pregnancy ≥12 weeks of gestational age. PARTICIPANTS/MATERIALS, SETTING, METHODS: A GnRH-agonist (n = 53) or GnRH-antagonist (n = 287) protocol was used for ovarian stimulation. Vaginal progesterone gel (Crinone, 90 mg, 8%, Merck) once daily was used for LPS. Serum P4 levels were measured in all patients on five occasions: on the day of ovulation trigger, the day of OPU, OPU + 3 days, OPU + 5 days and OPU + 14 days; timing of blood sampling was standardized to be 3-5 h after the morning administration of vaginal progesterone gel. The delta P4 (ΔP4) level was calculated by subtracting the P4 level on the OPU + 3 days from the P4 level on the OPU + 5 days, resulting in either a positive or negative ΔP4. MAIN RESULTS AND THE ROLE OF CHANCE: The median P4 (min-max) on the day of triggering, day of OPU, OPU + 3 days, OPU + 5 days and OPU + 14 days were 0.83 ng/ml (0.18-1.42), 5.81 ng/ml (0.80-22.72), 80.00 ng/ml (22.91-161.05), 85.91 ng/ml (15.66-171.78) and 13.46 ng/ml (0.18-185.00), respectively. Serum P4 levels uniformly increased from the day of OPU to OPU + 3 days in all patients; however, from OPU + 3 days to OPU + 5 days, some patients had a decrease (negative ΔP4; n = 116; 34.1%), whereas others had an increase (positive ΔP4; n = 220; 64.7%), in circulating P4 levels. Although the median (min-max) P4 levels on the day of triggering, the day of OPU, and OPU + 3 days were comparable between the negative ΔP4 and positive ΔP4 groups, patients in the former group had significantly lower P4 levels on OPU + 5 days [69.67 ng/ml (15.66-150.02) versus 100.51 ng/ml (26.41-171.78); P < 0.001] and OPU + 14 days [8.28 ng/ml (0.28-157.00) versus 19.01 ng/ml (0.18-185.00), respectively; P < 0.001]. A drop in P4 level from OPU + 3 days to OPU + 5 days (negative ΔP4) was seen in approximately one-third of patients and was associated with a significantly lower OPR when compared with positive ΔP4 counterparts [33.6% versus 49.1%, odds ratio (OR); 0.53, 95% CI; 0.33-0.84; P = 0.008]; this decrease in OPR was due to lower initial pregnancy rates rather than increased overall pregnancy loss rates. For negative ΔP4 patients, the magnitude of ΔP4 was a significant predictor of OP (adjusted AUC = 0.65; 95% CI; 0.59-0.71), with an optimum threshold of -8.73 ng/ml, sensitivity and specificity were 48.7% and 79.2%, respectively. BMI (OR; 1.128, 95% CI; 1.064-1.197) was the only significant predictor of having a negative ΔP4; the higher the BMI, the higher the risk of having a negative ΔP4. Among positive ΔP4 patients, the magnitude of ΔP4 was a weak predictor of OP (AUC = 0.56, 95% CI; 0.48-0.64). Logistic regression analysis showed that blastocyst morphology (OR; 5.686, 95% CI; 1.433-22.565; P = 0.013) and ΔP4 (OR; 1.013, 95% CI; 0.1001-1.024; P = 0.031), but not the serum P4 level on OPU + 5 days, were the independent predictors of OP. LIMITATIONS, REASONS FOR CAUTION: The physiological circadian pulsatile secretion of P4 during the mid-luteal phase is a limitation; however, blood sampling was standardized to reduce the impact of timing. WIDER IMPLICATIONS OF THE FINDINGS: Two measurements (OPU + 3 days and OPU + 5 days) of serum P4 may identify those patients with a drop in P4 (approximately one-third of patients) associated with ∼2-fold lower OPRs. Rescuing these IVF cycles with additional P supplementation or adopting a blastocyst freeze-all policy should be tested in future randomized controlled trials. STUDY FUNDING/COMPETING INTEREST(S): None. S.C.E. declares receipt of unrestricted research grants from Merck and lecture fees from Merck and Med.E.A. P.H. has received unrestricted research grants from MSD and Merck, as well as honoraria for lectures from MSD, Merck, Gedeon-Richter, Theramex, and IBSA. H.Y. declares receipt of honorarium for lectures from Merck, IBSA and research grants from Merck and Ferring. The remaining authors declare that they have no conflict of interest. TRIAL REGISTRATION NUMBER: The study was registered at clinical trials.gov (NCT04128436).

Birth size after embryo cryopreservation: larger by all measures?

STUDY QUESTION: Are the changes in birthweight after frozen and fresh embryo transfer associated with corresponding changes in other measures of foetal growth and placental efficiency? SUMMARY ANSWER: Although placental efficiency was reduced for both frozen and fresh embryo transfer, children born after frozen embryo transfer (frozen-ET) had symmetrically increased size at birth, whereas children born after fresh embryo transfer (fresh-ET) were asymmetrically smaller at birth, compared to naturally conceived children. WHAT IS KNOWN ALREADY: In pregnancies following frozen-ET, the risk of being born large, as measured by birthweight, is higher than after natural and fresh-ET conceptions. It is not known whether this is a result of symmetrically increased growth and increased placental efficiency. STUDY DESIGN, SIZE, DURATION: A Norwegian nationwide registry-based cohort study of 3093 singletons born after frozen-ET, 15 510 singletons born after fresh-ET and 1 125 366 singletons born after natural conception from 1988 to 2015 was performed. We identified 6334 sibships with at least two different conception methods. PARTICIPANTS/MATERIALS, SETTING, METHODS: Data were collected from the Medical Birth Registry of Norway and the Norwegian National Education Database. Main outcome measures were birth length, birthweight, head circumference, ponderal index (birthweight relative to birth length in kg/m3), placental weight, birthweight:placental weight ratio, gestational age, and birthweight z-score. We estimated mean differences between children born after frozen-ET and fresh-ET compared to natural conception, at the population level and within sibships. Adjustments were made for birth year, maternal age, parity, and education. MAIN RESULTS AND THE ROLE OF CHANCE: Estimates at the population level and within sibships were consistent for all outcomes, for both fresh and frozen-ET compared to natural conception. Within sibships, children born after frozen-ET had longer mean length (Δ = 0.42 cm, 95% CI 0.29 to 0.55) and head circumference (Δ = 0.32 cm, 95% CI 0.23 to 0.41) at birth, but a similar ponderal index (Δ = 0.11 kg/m3, 95% CI -0.04 to 0.26), compared to naturally conceived. Children born after fresh-ET had a shorter length (Δ = -0.22 cm, 95% CI -0.29 to -0.15) and head circumference (Δ = -0.15 cm, 95% CI -0.19 to -0.10), and lower ponderal index (Δ = -0.15 kg/m3, 95% CI -0.23 to -0.07) at birth compared to natural conception within sibships. Furthermore, mean placental weight was larger after both frozen-ET (Δ = 37 g, 95% CI 28 to 45) and fresh-ET (Δ = 7 g, 95% CI 2 to 13) compared to natural conception within sibships, whereas mean birthweight:placental weight ratio was reduced for both frozen-ET (Δ = -0.11, 95% CI -0.17 to -0.05) and fresh-ET (Δ = -0.13, 95% CI -0.16 to -0.09). A range of sensitivity analyses all gave similar conclusions as the main models, including restriction to full siblings, restriction to single embryo transfer, and adjustment for maternal BMI, height, and smoking. LIMITATIONS, REASONS FOR CAUTION: Additional adjustment for maternal BMI, height, and smoking was possible only for a small sample of the study population (15%). Data on causes and duration of infertility, as well as treatment details, were limited. WIDER IMPLICATIONS OF THE FINDINGS: The increased birthweight observed in singletons after frozen-ET is associated with a symmetrically increased birth size and large placentas, also after controlling for maternal factors through sibship analyses. Identifying the responsible treatment factors and the long-term health outcomes are particularly important considering the increase in elective freezing of all embryos. STUDY FUNDING/COMPETING INTEREST(S): This work was partly supported by the Central Norway Regional Health Authorities (project number 46045000), the Norwegian University of Science and Technology (project number 81850092) and the Research Council of Norway through its Centres of Excellence funding scheme (project number 262700). The authors have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: N/A.

High anti-Müllerian hormone (AMH) is associated with increased risks of ectopic pregnancy in women undergoing fresh embryo transfer cycle, a cohort study.

BACKGROUND: Ectopic pregnancy is more common amongst assisted reproduction cycles and is a cause of significant maternal morbidity. Few predictive markers exist to help identify and modify risk of ectopic pregnancy in preparing for embryo transfer. The relationship between serum and AMH and ectopic pregnancy rate is unknown. METHODS: This was a retrospective cohort study investigating women who underwent fresh embryo transfer cycles from January 2017 to December 2019 in Peking University Third Hospital. The primary outcome was ectopic pregnancy. Restricted cubic splines with four knots for AMH concentration (0-3, 3-6, 6-12, 12-max) were used to map out the non-linear relationship between the predicted ectopic pregnancy rate and the serum AMH concentration. Log binomial regression was used to test the crude risk ratio (cRR) and the adjusted risk ratio (aRR) after adjustment for confounders with 95% confidence intervals (CI) to determine the difference across various groups. RESULTS: A total of 13,718 cycles in women undergoing fresh embryo transfer were eligible for analysis. The ectopic pregnancy rate was 1.3% per embryo transfer cycle initiated and 3.3% per pregnancy. Serum AMH concentrations were higher amongst women with ectopic pregnancy than in women with a confirmed intrauterine pregnancy or heterotopic pregnancy or who did not become pregnant (Mean levels: 4.0 ng/ml vs 3.2 ng/ml, 1.7 ng/ml, and 2.8 ng/ml). An AMH concentration of 7 ng/ml represented the best cut-off value to predict ectopic pregnancy. The ectopic pregnancy rate was 3.4% per cycle and 7.5% per pregnancy in women with AMH levels ≥ 7 ng/ml; and 1.2% per cycle and 2.9% per pregnancy in women with AMH levels < 7 ng/ml. Serum AMH concentration ≥ 7 ng/ml was associated with an increased risk of ectopic pregnancy in all fresh embryo transfer cycles started (aRR = 2.35 (1.45, 3.58)) as well in women who became pregnant (aRR = 2.23 (1.49, 3.33). CONCLUSIONS: Baseline AMH concentration ≥ 7 ng/ml is associated with an increased risk of ectopic pregnancy in fresh embryo transfer cycles.

Risk factors for clinical pregnancy loss after IVF in women with PCOS.

RESEARCH QUESTION: Which factors are associated with the risk of clinical pregnancy loss in women with polycystic ovary syndrome (PCOS) undergoing IVF? DESIGN: Case-control study nested in a multicentre randomized trial comparing live birth rates between fresh and frozen embryo transfer in women with PCOS. Women with the outcome of clinical pregnancy loss were selected as the case group, those with live birth as the control group. Parameters before IVF treatment and variables during ovarian stimulation and embryo transfer were compared. RESULTS: Women with clinical pregnancy loss had higher maternal body mass index (BMI, P = 0.010), anti-Müllerian hormone (AMH, P = 0.032), 2-h glucose concentration after 75 g oral glucose tolerance test (OGTT, P = 0.025), and a higher proportion of fresh embryo transfers (P = 0.001). There were significant interactions between the types of transfer and antral follicle count (AFC, P = 0.013), 2-h glucose concentration after OGTT (P = 0.024) on clinical pregnancy loss in PCOS, indicating that these factors may have different effects on pregnancy loss after fresh versus frozen embryo transfer. When the multivariable logistic regression analysis was stratified by the fresh or frozen embryo transfer, AFC (adjusted odds ratio [aOR] 1.03, 95% confidence interval [CI] 1.01-1.05) was a risk factor for clinical pregnancy loss after fresh embryo transfer, while 2-hour glucose concentration after OGTT (aOR 1.13, 95% CI 1.01-1.25) was associated with clinical pregnancy loss in frozen embryo transfer (FET) cycles. CONCLUSIONS: In women with PCOS, fresh embryo transfer, higher BMI, AFC and 2-h glucose concentration after OGTT were risk factors for clinical pregnancy loss. FET may be a better choice to decrease the risk of clinical pregnancy loss, especially for those with higher AFC. During FET, 2-h glucose after OGTT appears to be associated with clinical pregnancy loss and warrants close monitoring.

Suitable endometrial thickness on embryo transfer day may reduce ectopic pregnancy rate and improve clinical pregnancy rate.

BACKGROUND: This retrospective study aimed to investigate the most suitable endometrial thickness (EMT) on the day of embryo transfer that could reduce ectopic pregnancy rate (EPR) and improve clinical pregnancy rate (CPR) in fresh embryo transfer patients with early follicular phase long-acting regimen. METHODS: A total of 11,738 IVF/ICSI cycles, comprising 4,489 non-clinical pregnancies, 7,121 intrauterine pregnancies, and 128 ectopic pregnancy cycles after fresh embryo transfer, recorded between September 2017 and December 2020. Clinical pregnancy (CP) and ectopic pregnancy (EP) were the primary outcomes. Multivariate logistic regression was used to calculate the adjusted odds ratio (aOR) and 95% confidence interval (CI) for EP and CP. Patients were divided into three groups based on the EMT (6-10 mm, 11-15 mm, and 16-20 mm). CPR and EPR per millimeter of EMT were drawn into a line chart, and three groups were analyzed by Chi-square test. RESULTS: After controlling for potential confounders, EMT had a significant effect on CP (aOR = 1.07; 95% CI, 1.05-1.08; P = 0.00) and EP (aOR = 0.88; 95% CI, 0.82-0.94; P = 0.00). With the increase of EMT, CPR increased and EPR decreased. Pearson correlation coefficients were r = 0.708 (P = 0.00) and r =-0.558 (P = 0.03), respectively. Significant differenceswere detected in the CPRs and EPRs (all P = 0.00). The CPR in the 6-10 mm group (54.88%) was significantly lower than that in the 11-15 mm group (64.23%) and the 16-20 mm group (64.40%) (P = 0.00). The EPR in the 6-10 mm group (2.72%) was significantly higher than that in the other two groups (1.60% and 0.97%, P = 0.00). The difference in CPR and EPR between the 11-15 mm group and the 16-20 mm group was not statistically significant, which indicated that EMT ≥ 11 mm simultaneously reduced the EPR and increased the CPR. CONCLUSIONS: EMT was inversely proportional to EPR and directly proportional to CPR in fresh embryo transfer cycles. The EMT ≥ 11 mm on the day of embryo transfer could simultaneously achieve lower EPR and higher CPR. Accordingly, more attention should be given to the EMT of women who underwent ART treatment.

The effect of luteinizing hormone changes in GnRH antagonist protocol on the outcome of controlled ovarian hyperstimulation and embryo transfer.

BACKGROUD: To investigate the effect of Luteinizing hormone (LH) level changes on the outcomes of controlled ovarian hyperstimulation (COH) and embryo transfer (ET) in gonadotropin-releasing hormone antagonist (GnRH-ant) protocol. METHODS: A total of 721 patients undergoing GnRH-ant protocol COH for the first IVF/ICSI cycles were retrospectively analyzed. COH process were divided into 2 stages, before (stage 1) and after (stage 2) the GnRH-ant initiation, and each with 5 groups basing on LH levels: LH decreased more than 50% (groups A1, A2), decreased 25-50% (groups B1, B2), change less than 25% (groups C1, C2), increased 25-50% (groups D1, D2), and increased more than 50% (groups E1, E2). RESULTS: There were no significant differences among groups of stage1 regarding COH and ET outcomes. For stage 2, the more obvious the decrease of LH level, the more the number of oocytes retrieved, mature oocytes, fertilized oocytes, embryos cleavaged and the numbers of embryo available (P < 0.05), but without significant differences regarding ET outcomes. We also found the freeze-all rate in Group A2 was higher (P < 0.001). CONCLUSION: LH level changes before GnRH-ant addition were not related to COH and ET outcomes. LH level changes after the addition of GnRH-ant were related to the outcome of COH, and no significant differences were found relating to ET outcomes.

Effects of reduced follicle-stimulating hormone dosage before human chorionic gonadotropin trigger on in vitro fertilization outcomes.

OBJECTIVE: To determine whether a reduced dose of follicle-stimulating hormone (FSH) before human chorionic gonadotropin (hCG) trigger during ovarian stimulation can affect in vitro fertilization (IVF) outcomes. METHODS: This study included 347 patients with a normal ovarian response who received a reduced dose of FSH before hCG trigger for 2-3 days (Group A) and 671 patients who did not receive a reduced dose (Group B) from a university-affiliated IVF center between January 2021 and December 2022. The primary endpoint was estrogen (E2) and progesterone (P) levels on the day of hCG trigger, fresh embryo transfer cycles, laboratory outcomes, and clinical outcomes between the two groups. RESULTS: On the day of hCG trigger, Group A had significantly lower E2 and P levels than those in Group B (3454.95 ± 1708.14 pg/mL versus 3798.70 ± 1774.26 pg/mL, p = 0.003; and 1.23 ± 0.53 ng/mL versus 1.37 ± 0.59 ng/mL, p < 0.001, respectively). The proportion of patients with P levels ≥ 1.5 ng/mL was 22.48% in Group A compared to 34.58% in Group B (p < 0.001), while the proportion of patients with E2 ≥ 5000 pg/mL was 15.27% in Group A compared to 25.93% in Group B (p < 0.001). The fresh embryo-transfer cycle rate in Group A was higher than that in group B (54.47% and 32.64%, respectively; p < 0.001). Despite the reduction in FSH dosage, there were no significant differences between groups regarding the number of oocytes retrieved, total number of mature oocytes, normal fertilization rate, cleavage rate, Day 3 top-quality rate, implantation rate, pregnancy rate per cycle, and early pregnancy loss rate. CONCLUSION: While a reduced dose of FSH prior to hCG trigger during ovarian stimulation did not significantly affect IVF outcomes, it was associated with lower E2 and P levels, resulting in fewer cycles with E2 ≥ 5000 pg/mL and P ≥ 1.5 ng/mL on the day of the hCG trigger.

The gestational age-specific difference in birthweight between singletons born after fresh and frozen embryo transfer: A cohort study.

INTRODUCTION: Accumulating studies have suggested singletons born after frozen embryo transfer (FET) were higher than those born after fresh embryo transfer (Fre-ET). However, fewer studies had investigated the gestational age-specific between-group difference in birthweight. This study aimed to investigate the gestational week-specific difference in singleton birthweight after FET vs Fre-ET and explore potential factors that impact the difference. MATERIAL AND METHODS: In this retrospective cohort study, a total of 25 863 singletons were included. Multivariable linear regression and logistic regression were used to evaluate the between-group differences in mean birthweight and the incidences of large for gestational age (LGA) and small for gestational age (SGA), respectively. RESULTS: Multivariable regression analyses showed a statistically significant interaction between types of embryo transfer (ie FET vs Fre-ET) and the gestational week on mean birthweight (P < 0.001) and on the risks of large for gestational age (P = 0.001) and small for gestational age (P < 0.001). When stratified by gestational week, the differences in mean birthweight and the risks of LGA and SGA were only observed in singletons born at 37 gestational weeks or later. After adjusting for confounders, full-term but not preterm singletons born after FET had a higher birthweight (3497.58 ± 439.73 g vs 3445.67 ± 450.24 g; adjusted mean difference 58.35 g; 95% confidence interval [CI] 38.72-77.98 g), a higher risk of LGA (24.3% vs 21.1%; adjusted odds ratio [OR] 1.28, 95% CI 1.15-1.42) and a lower risk of SGA (3.1% vs 4.8%; adjusted OR 0.61, 95% CI 0.53-0.70) compared with those born after Fre-ET. CONCLUSIONS: The differences in birthweight between FET and Fre-ET were observed in full-term singletons but not preterm singletons.

Is artificial endometrial preparation more associated with early-onset or late-onset preeclampsia after frozen embryo transfer?

PURPOSE: To explore whether the risks of early- or late-onset preeclampsia vary among frozen embryo transfer (FET) with different regimens for endometrial preparation and fresh embryo transfer (FreET). METHODS: We retrospectively included a total of 24129 women who achieved singleton delivery during their first cycles of in vitro fertilization (IVF) between January 2012 and March 2020. The risks of early- and late-onset preeclampsia after FET with endometrial preparation by natural ovulation cycles (FET-NC) or by artificial cycles (FET-AC) were compared to that after FreET. RESULTS: After adjustment via multivariable logistic regression, the total risk of preeclampsia was higher in the FET-AC group compared to the FreET group [2.2% vs. 0.9%; adjusted odds ratio (aOR): 2.00; 95% confidence interval (CI): 1.45-2.76] and FET-NC group (2.2% vs. 0.9%; aOR: 2.17; 95% CI: 1.59-2.96).When stratified by the gestational age at delivery based on < 34 weeks or ≥ 34 weeks, the risk of late-onset preeclampsia remained higher in the FET-AC group than that in the and FreET group (1.8% vs. 0.6%; aOR: 2.56; 95% CI: 1.83-3.58) and the FET-NC group (1.8% vs. 0.6%; aOR: 2.63; 95% CI: 1.86-3.73). We did not find a statistically significant difference in the risk of early-onset preeclampsia among the three groups. CONCLUSIONS: An artificial regimen for endometrial preparation was more associated with an increased risk of late-onset preeclampsia after FET. Given that FET-AC is widely used in clinical practice, the potential maternal risk factors for late-onset preeclampsia when using the FET-AC regimen should be further explored, considering the maternal origin of late-onset preeclampsia.

Comparison of uterine, endometrial and subendometrial blood flows in predicting pregnancy outcomes between fresh and frozen-thawed embryo transfer after GnRH antagonist protocol: a retrospective cohort study.

This retrospective cohort study aimed to compare endometrial receptivity and pregnancy rate between fresh embryo transfer (ET) and frozen-thawed ET after gonadotrophin-releasing hormone (GnRH) antagonist protocol in normal ovarian responders. The patients were divided into two groups: the fresh ET group and the frozen-thawed ET group. Uterine artery resistance index (RI) and endometrial thickness were lower in the frozen-thawed ET group. The proportion of detectable endometrial-subendometrial flow was significantly higher in the frozen-thawed ET group. There was no significant difference in miscarriage rate between the two groups. Frozen-thawed ET group had a significantly higher CPR (56.0% vs. 48.1%), implantation rate (32.2% vs. 26.4%), and LBR (45.4% vs. 36.5%) than the fresh ET group. In GnRH antagonist protocol, elective frozen-thawed ET should be ideally taken, as this could improve embryo implantation rate, clinical pregnancy rate, and live birth rate, thus presenting an effective strategy to enhance the embryo utilization rate.IMPACT STATEMENTWhat is already known on this subject? The clinical pregnancy rate following fresh embryo transfer (ET) was lower than frozen-thawed ET after GnRH antagonist protocol. IVF success depends on embryo quality, embryo-endometrium interaction and endometrial receptivity. A good blood supply toward the endometrium is generally considered a requirement for implantation.What do the results of this study add? Uterine artery RI and endometrial thickness were significantly lower in the frozen-thawed ET group. The proportion of detectable endometrial-subendometrial flow was significantly higher in the frozen-thawed ET group. Frozen-thawed ET group had a significantly higher clinical pregnancy rate, implantation rate and live birth rate than the fresh ET group after GnRH antagonist protocol.What are the implications of these findings for clinical practice and/or further research? In GnRH antagonist protocol, elective frozen-thawed ET should be ideally taken, as this could improve embryo implantation rate, clinical pregnancy rate and live birth rate, thus presenting an effective strategy to enhance the embryo utilization rate.

Anthropometric measurements of term singletons at 6 years of age born from fresh and frozen embryo transfer: A multicenter prospective study in Japan.

Purpose: The purpose of this study is to compare anthropometric measurements between term singletons conceived via fresh embryo transfer (FreET) and frozen embryo transfer (FET) and those born via natural conception (NC) or fertility treatments milder than assisted reproductive technology (non-ART) at 6 years of age. Methods: A total of 8149 children were enrolled, and questionnaires about anthropometric measures (weight, height, BMI) were addressed to parents, when the children were 1.5, 3, and 6 years of age. A total of 3299 term singletons were enrolled at birth: 533, 476, 916, and 1374 in the NC, non-ART, FreET, and FET groups, respectively. Results: A total of 1635 term singletons (290, 176, 467, and 702 in the NC, non-ART, FreET, and FET groups respectively) were enrolled until 6 years of age (follow-up rate, approximately 50%). When non-ART group was used as control, the FreET children were 1.0 cm taller than the non-ART children at 6 years of age, after adjusting for confounding factors. However, no differences were observed in the anthropometric data among the non-ART, ART, and NC children at 6 years of age. Conclusion: At 6 years of age, term singletons were taller in the FreET group than in the non-ART group, after adjusting for confounders.