Estimating the impact of bias in causal epidemiological studies: the case of health outcomes following assisted reproduction.

Researchers interested in causal questions must deal with two sources of error: random error (random deviation from the true mean value of a distribution), and bias (systematic deviance from the true mean value due to extraneous factors). For some causal questions, randomization is not feasible, and observational studies are necessary. Bias poses a substantial threat to the validity of observational research and can have important consequences for health policy developed from the findings. The current piece describes bias and its sources, outlines proposed methods to estimate its impacts in an observational study, and demonstrates how these methods may be used to inform debate on the causal relationship between medically assisted reproduction (MAR) and health outcomes, using cancer as an example. In doing so, we aim to enlighten researchers who work with observational data, especially regarding the health effects of MAR and infertility, on the pitfalls of bias, and how to address them. We hope that, in combination with the provided example, we can convince readers that estimating the impact of bias in causal epidemiologic research is not only important but necessary to inform the development of robust health policy and clinical practice recommendations.

Pro: Fresh versus frozen embryo transfer. Is frozen embryo transfer the future?

Embryo cryopreservation has been an integral part of ART for close to 40 years and vitrification has boosted overall ART efficacy and safety. Recently, there has been a vivid scientific discussion on whether elective cryopreservation of all embryos (freeze-all) should be pursued for most patients, with a fresh embryo transfer taking place only in selected cases. In terms of efficacy, the available evidence suggests that the freeze-all strategy leads to higher live birth rates after the first embryo transfer compared to the conventional strategy in high responders, while there is no difference in normal responders. There is no evidence to suggest that the freeze-all strategy is inferior to the conventional strategy of fresh transfer when comparing cumulative live birth rates using data from all available randomized controlled trials. The incidence of ovarian hyperstimulation syndrome is significantly reduced in the freeze-all policy. However, regarding obstetric complications and neonatal outcomes, the evidence suggests that each strategy is associated with certain risks and, therefore, there is no approach that could be unequivocally accepted as safer. Similarly, limited evidence does not support the notion that patients would be universally against freeze-all owing to the inevitable delay in pregnancy achievement. Finally, the cost-effectiveness of freeze-all is likely to vary in different settings and there have been studies supporting that this policy can be, under certain conditions, cost-effective. Adoption of the freeze-all policy can also allow for more flexible treatment strategies that have the potential to increase efficacy, reduce cost and make treatment easier for patients and clinics. Importantly, freeze-all does not require the use of any experimental technologies, further training of personnel or the costly acquisition of new equipment. For these reasons, transitioning to the freeze-all policy for most patients appears to be the next logical step in ART.

Biosimilar recombinant follitropin alfa preparations versus the reference product (Gonal-F®) in couples undergoing assisted reproductive technology treatment: a systematic review and meta-analysis.

BACKGROUND: Live birth has increasingly been identified as the standard clinical approach to measure the success of medically assisted reproduction (MAR). However, previous analyses comparing biosimilar preparations of follitropin alfa versus the reference product (GONAL-f®, Merck KGaA, Darmstadt, Germany or GONAL-f® RFF; EMD Serono, Inc., Rockland, MA), have had insufficient power to detect differences in clinically meaningful outcomes such as live birth. METHODS: Medline, Embase, the Cochrane Library, Web of Science and clinical trial registries were searched for randomised controlled trials (RCTs) and conference abstracts comparing biosimilar follitropin alfa versus the reference product in controlled ovarian stimulation (COS) cycles published before 31 October 2020. Only studies in humans and publications in English were included. Retrieved studies were screened independently by two authors based on titles and abstracts, and then by full text. INCLUSION CRITERIA: RCTs comparing follitropin alfa biosimilar preparations with the reference product in infertile patients of any age, with any type of infertility for any duration, undergoing COS for the purposes of MAR treatment (including frozen cycles). The primary outcome was live birth. Combined data for biosimilar preparations were analysed using a fixed-effects model. RESULTS: From 292 unique records identified, 17 studies were included in the systematic review, representing five unique RCTs that were included in the meta-analysis. Rates of live birth (RR = 0.83, 95% CI 0.71, 0.97; 4 RCTs, n = 1881, I2 = 0%), clinical pregnancy (RR = 0.82, 95% CI 0.72, 0.94; 4 RCTs, n = 2222, I2 = 0%) and ongoing pregnancy (RR = 0.81, 95% CI 0.68, 0.96; 4 RCTs, n = 1232, I2 = 0%) were significantly lower with biosimilar preparations versus the reference product. Rates of cumulative live birth and cumulative clinical pregnancy were also significantly lower with biosimilars versus the reference product. There was high risk of publication bias. CONCLUSIONS: This meta-analysis included data from RCTs evaluating the efficacy and safety of the biosimilar follitropin alfa preparations and demonstrated lower probability of live birth and pregnancy (ongoing and clinical) in couples treated with biosimilar preparations compared with the reference product. This study provides more insight into the differences between biosimilar r-hFSH preparations and the reference product than previously reported. TRIAL REGISTRATION: Registration number: CRD42019121992 .

Female age is associated with the optimal number of oocytes to maximize fresh live birth rates: an analysis of 256,643 fresh ART cycles.

RESEARCH QUESTION: What is the optimal number of oocytes retrieved at which maximum live birth rate is observed after fresh autologous assisted reproductive technology (ART) cycles for women of different ages? DESIGN: Retrospective cohort study of all fresh autologous ART aspiration cycles (n = 256,643) undertaken in Australia and New Zealand between 2009 and 2015. Primary outcome measure was live birth rate (LBR) (delivery of at least one liveborn baby at 20 weeks' gestation or over per fresh aspiration cycle). Cycles were grouped according to female age (<30, 30-34, 35-49, 40-44 and ≥45 years) and ovarian response (one to three, four to nine, 10-14, 15-19, 20-25 and ≥25 oocytes). Secondary outcome was incidence of ovarian hyperstimulation syndrome (OHSS) requiring hospitalization. RESULTS: At different oocyte yields, LBR per fresh aspiration cycle peaked and then declined at, depending on female age: <30 years: six to 11 oocytes (LBR 31-34%); 30-34 years: 11-16 oocytes (LBR 29-30%); 35-39 years: nine to 17 oocytes (LBR 21-24%); and 40-44 years: 15-17 oocytes (LBR 11-12%). The incidence of OHSS increased significantly with the number of oocytes retrieved, from 1.2% with 15 oocytes retrieved to 9.3% with 30 or more oocytes retrieved (P < 0.001). CONCLUSION: The optimal number of oocytes at which maximum LBR was observed in a fresh aspiration cycle was highly dependent on age. Because of the observational nature of the results, a cause-effect relationship between the number of oocytes retrieved and LBR should not be assumed; evidence from well-designed randomized control trials is required before clinical advice can be suggested.

Is there an optimal number of oocytes retrieved at which live birth rates or cumulative live birth rates per aspiration are maximized after ART? A systematic review.

The association between the number of oocytes retrieved and fresh live birth rate (LBR) or cumulative LBR (CLBR), and whether an optimal number of oocytes are retrieved when LBR or CLBR are maximized, are highly relevant clinical questions; however published results are conflicting. A systematic review of all eligible studies (n = 16) published until January 2020 on MEDLINE, Embase, Scopus, CINAHL and Web of Science was conducted. Five studies evaluated only LBR from fresh cycles, five studies evaluated only CLBR from stimulated cycles and six evaluated both. A marked difference was observed between the oocyte yields at which LBR and CLBR were reportedly maximized in the individual studies. On the basis of nine studies, the optimal number of oocytes at which fresh LBR seems to be maximized is proposed to be between 12 and 18 oocytes (15 oocytes was the most common suggestion). On the other hand, CLBR continues to increase with the number of oocytes retrieved. This is the first systematic review on the topic, and it suggests that the retrieval of 12-18 oocytes is associated with maximal fresh LBR, whereas a continuing positive association is present between the number of oocytes retrieved and CLBR.

Association between body mass index and oocyte maturation in patients triggered with GnRH agonist who are at high risk for severe ovarian hyperstimulation syndrome: an observational cohort study.

RESEARCH QUESTION: Is body-mass index (BMI) associated with oocyte maturation in women at high risk for developing severe ovarian hyperstimulation syndrome (OHSS) who are triggered with gonadotrophin releasing hormone (GnRH) agonist? DESIGN: Prospective observational cohort study. A total of 113 patients at high risk for severe OHSS (presence of at least 19 follicles ≥11 mm) pre-treated with gonadotrophin releasing hormone (GnRH) antagonists and recombinant FSH were administered 0.2 mg triptorelin to trigger final oocyte maturation. Patients were classified in two groups depending on their BMI: ΒΜΙ less than 25 kg/m2 (n = 72) and ΒΜΙ 25 kg/m2 or over (n = 41). Baseline, ovarian stimulation and embryological characteristics, as well as luteal-phase hormone profiles, were compared in patients classified into the two BMI groups. The main outcome measure was the number of mature oocytes. RESULTS: A significantly higher number of mature (metaphase II) oocytes (19 [18-21] versus 16 [13-20], P = 0.029) was present in women with BMI less than 25 kg/m2 compared with those with BMI 25 kg/m2 or greater. The number of retrieved oocytes, the number of fertilized oocytes, oocyte retrieval, maturation and fertilization rates were similar in the two groups. A significantly higher dose of recombinant FSH was required for patients with BMI 25 kg/m2 or greater compared with patients with BMI less than 25 kg/m2 (1875 [1650-2150] IU versus 1650 [1600-1750] IU, P = 0.003) and the two groups displayed different luteal phase hormonal profiles. CONCLUSIONS: Among women at high risk for developing severe OHSS who are triggered with a standard dose (0.2 mg) of the GnRH agonist triptorelin, women with BMI 25 kg/m2 or greater had significantly fewer mature oocytes, required a higher total dose of recombinant FSH compared with women with BMI less than 25 kg/m2.

Is more better? A higher oocyte yield is independently associated with more day-3 euploid embryos after ICSI.

STUDY QUESTION: Is the number of oocytes retrieved after ovarian stimulation for ICSI independently associated with the number of day-3 euploid embryos (EE)? SUMMARY ANSWER: A larger oocyte yield is independently associated with more day-3 EE, although the expected benefit decreases significantly with advancing age. WHAT IS KNOWN ALREADY: Although traditionally ovarian stimulation aims at collecting more than one oocyte in order to increase the chance of pregnancy, there is evidence suggesting that excessive ovarian response leads to lower live birth rates. Whether a larger oocyte yield after ovarian stimulation is associated with the genetic composition of the resulting embryos and therefore with their reproductive potential is still largely unknown. STUDY DESIGN, SIZE, DURATION: This is a multi-centered retrospective cohort study analyzing 724 cycles of preimplantation genetic testing for aneuploidy (PGT-A) cycles using day-3 biopsy and array-comparative genomic hybridization between March 2011 and December 2016 in three laboratories. PARTICIPANTS/MATERIALS, SETTING, METHODS: The primary outcome measure was the number of EE on day-3. Statistical analysis was performed using the generalized estimating equations (GEE) framework and multivariate regression models to control for the clustered nature of the data while adjusting for potential confounders. MAIN RESULTS AND THE ROLE OF CHANCE: A multivariate regression GEE model including all significant population and stimulation characteristics as covariates as well as an interaction term between female age and number of oocytes revealed that the number of oocytes retrieved was still positively associated with the number of EE (coeff: +0.40, 95% CI: 0.24-0.56). The interaction term was highly significant (coeff: -0.01, P < 0.001) indicating an effect modifying role of female age on the association of oocytes retrieved with the number of EE. The number of oocytes retrieved was also positively associated with cumulative live birth rates (odds ratio: 1.07, 95% CI: 1.03-1.12). LIMITATIONS, REASONS FOR CAUTION: This study is retrospective and the presence of residual unknown bias cannot be excluded. Furthermore, the population analyzed in this study might not be completely representative of the general population undergoing ICSI. WIDER IMPLICATIONS OF THE FINDINGS: These results provide an explanatory mechanism for the recently published positive association between the number of oocytes retrieved and cumulative live birth rates. STUDY FUNDING/COMPETING INTEREST(S): CAV is supported by a NHMRC Early Career Fellowship (GNT1147154)/ No competing interests to declare.

The number of oocytes associated with maximum cumulative live birth rates per aspiration depends on female age: a population study of 221 221 treatment cycles.

STUDY QUESTION: What is the number of oocytes where the maximum cumulative live birth rate per aspiration (CLBR) is observed during ART in women of different ages? SUMMARY ANSWER: The maximum CLBR was observed when around 25 oocytes were retrieved in women between 18-35 years of age, around 9 oocytes in women more than 45 years of age and continued to increase beyond 30 oocytes in women between 36-44 years of age. WHAT IS KNOWN ALREADY: The live birth rate per fresh or frozen/thaw embryo transfer (FET) procedure has traditionally been the main measure of ART success. However, with the introduction of highly efficient embryo cryopreservation methods, CLBR encompassing live delivery outcomes from the fresh and all subsequent FET following a single ovarian stimulation and oocyte collection is increasingly viewed as a more meaningful measure of treatment success. There is evidence suggesting that larger oocyte yields are associated with increased likelihood of cumulative live birth per aspiration. Whether this association is the same across female ages has not yet been properly investigated. STUDY DESIGN, SIZE, DURATION: This is a large retrospective population-based cohort study using data from the Australian and New Zealand Assisted Reproduction Database (ANZARD). ANZARD contains information from all ART treatment cycles carried out in all fertility centres in Australia and New Zealand. Overall, 221 221 autologous oocyte aspiration cycles carried out between January 2009 to December 2015 were included in the analysis. PARTICIPANTS/MATERIALS, SETTING, METHODS: Cumulative live birth per aspiration was defined as at least one liveborn baby at ≥20 weeks gestation resulting from an ART aspiration cycle, including all fresh and FET resulting from the associated ovarian stimulation, until one live birth occurred or all embryos were used. Cycles where no oocytes were retrieved were excluded from analysis as there is no possibility of live birth. Analyses of data were performed using generalized estimating equations to account for the clustered nature of data (multiple cycles undertaken by a woman). Univariate and multivariable regression analysis was performed to identify and adjust for factors known to independently affect cumulative live birth per aspiration. An interaction term between female age and the number of oocytes retrieved was included to assess whether the age of the women was associated with a different optimal number of oocytes to achieve at least one live birth from an aspiration cycle (i.e. the effect-modifying role of female age). The likelihood of cumulative live birth per aspiration was calculated as odds ratios (ORs) with 95% CI. MAIN RESULTS AND THE ROLE OF CHANCE: The median number of oocytes retrieved was 7 (interquartile range, 4-12) and median age of patients was 36 (interquartile range, 33-40). The overall CLBR was 32.2%. The results from the multivariable regression analysis showedthat the number of oocytes retrieved remained a significant predictor (P < 0.001) of cumulative live birth per aspiration after adjusting for female age, parity and cycle count. Compared to the reference group of 10-14 oocytes retrieved, the adjusted odds for cumulative live birth per aspiration increased with the number of oocytes retrieved: 1-3 oocytes, 0.21 (95% CI, 0.20-0.22); 4-9 oocytes, 0.56 (95% CI, 0.55-0.58); 15-19 oocytes, 1.38 (95% CI, 1.34-1.43); 20-24 oocytes, 1.75 (95% CI, 1.67-1.84); and 2.10 (95% CI, 1.96-2.25) with more than 25 oocytes. After stratifying by female age group, the rate of increase in CLBR per additional oocyte retrieved was lower in the older age groups, indicating that higher oocyte yields were more beneficial in younger women. CLBR of patients in the <30 years and 30-34 years age groups appeared to reach a plateau (with only minimal increase in CLBR per additional oocyte retrieved) after retrieval of 25 oocytes at 73% and 72%, respectively, while CLBR of patients in the 35-39 years and 40-44 years age groups continued to increase with higher oocyte yields, reaching 68% and 40%, respectively, when 30 or more oocytes were retrieved. CLBR of patients aged 45 years and above remained consistently below 5%. Findings suggest that the number of oocytes retrieved where CLBR appears to be maximized is around 25 in women between 18-35 years, more than 30 in women between 36-44 years and around 9 in women 45 years and older. However, results for women aged 45 years and older may not be as robust due to the relatively small sample size available in this age group. LIMITATIONS, REASONS FOR CAUTION: As with all large retrospective database studies, there are potential confounders that cannot be accounted for. Despite the current study being based on complete ascertainment of ART cycles across two countries, ovarian stimulation protocols, oocyte quality parameters and a number of important patient characteristics are not collected by ANZARD. Additionally, a small number of cycles were available for women over 45 years yielding more than 15 oocytes, making these estimates unreliable. WIDER IMPLICATIONS OF THE FINDINGS: The results from this study demonstrate that the number of oocytes retrieved where the maximum CLBR is observed during ART is dependent on female age. This provides information for clinicians and patients to understand the modifying effect of age on the number of oocytes retrieved and the likelihood of success with ART. STUDY FUNDING/COMPETING INTEREST(S): No external funding was used for this study. The Fertility Society of Australia funds the National Perinatal Epidemiology and Statistics Unit to manage ANZARD and conduct national reporting of ART in Australia and New Zealand. Associate Professor Georgina Chambers (G.C.) is employed by the University of New South Wales (UNSW) and is director of the National Perinatal Epidemiology and Statistics Unit at UNSW. G.C. was also a paid member of the Australian governments Medicare Benefits Scheme taskforce on assisted reproductive technologies in 2017.

Fine-tuning blastocyst selection based on morphology: a multicentre analysis of 2461 single blastocyst transfers.

RESEARCH QUESTION: Which blastocyst morphology parameter is associated with live birth after controlling for female age and endometrial receptivity? DESIGN: Retrospective study including fresh single blastocyst transfers (n = 2461) where the value of serum progesterone on day of human chorionic gonadotrophin trigger (PdHCG) was available. Generalized estimating equation regression models evaluated the independent effects of developmental stage (DevSt), inner cell mass (ICM) and trophectoderm grade on live birth rates while controlling for the confounding effects of female age and PdHCG. RESULTS: DevSt was strongly associated with the probability of live birth (P < 0.0001) independently of female age (odds ratio [OR] 0.89, 95% confidence interval [CI] 0.87-0.91) and PdHCG (OR 0.80, 95% CI 0.74-0.87). For full blastocysts, expanded blastocysts and hatching blastocysts, addition of ICM and trophectoderm grading in the multivariable analysis suggested that besides female age (OR 0.92, 95% CI 0.90-0.94) and PdHCG (OR 0.80, 95% CI 0.73-0.87), only DevSt (P = 0.001) and trophectoderm quality (P = 0.004) were independent predictors of live birth, while the predictive capacity of ICM was no longer significant. The mean probability of live birth was highest for AA blastocysts (35.0%), followed by BA blastocysts (31.2%) and AB blastocysts (27.7%). CONCLUSION: This large study analyses for the first time the independent role of blastocyst morphology in predicting live birth while controlling for female age and PdHCG. Its findings suggest that DevSt and then trophectoderm grade are stronger predictors of live birth over ICM grade when selecting a single blastocyst for transfer.

Is there an association between oocyte number and embryo quality? A systematic review and meta-analysis.

This systematic review and meta-analysis determined the association between aspirated after ovarian stimulation and top/good quality embryos obtained in women undergoing ovarian stimulation for IVF/intracytoplasmic sperm injection (ICSI). MEDLINE, EMBASE, Scopus, CINAHL and Web of Science were searched for English-language publications on top/good-quality embryos at cleavage (day 2/3) and/or blastocyst (day 5/6) developmental stages, up to 18 November 2017. Twenty-eight studies (three prospective and 25 retrospective) reporting data on 291,752 assisted reproductive technology (ART) cycles were considered eligible. We confirmed a strong positive association between oocytes retrieved and top/good-quality day 2/3 embryos (weighted correlation coefficient [rw] = 0.791), day 5/6 embryos (rw = 0.901), metaphase II oocytes (rw = 0.988), oocytes exhibiting two pronuclei (rw = 0.987) and euploid embryos (rw = 0.851); P < 0.001 for all correlations (evaluated in subsets of the 17 studies). Data from 5657 cycles showed that the group with the most oocytes aspirated had the most top/good-quality day 2/3 embryos (pooled standardized mean differences (high [>15] versus low [<4] 1.91, 95% confidence interval [CI] 1.05-2.77, P < 0.0001; high versus medium [4-15] 1.15, 95% CI 0.74-1.55, P < 0.0001; medium versus low 1.41, 95% CI 0.79-2.03, P < 0.0001). Individual participant meta-analysis would enable accurate determination of these associations and other outcomes.

Inter-observer and intra-observer agreement between embryologists during selection of a single Day 5 embryo for transfer: a multicenter study.

STUDY QUESTION: What is the inter-observer and intra-observer agreement between embryologists when selecting a single Day 5 embryo for transfer? SUMMARY ANSWER: The inter-observer and intra-observer agreement between embryologists when selecting a single Day 5 embryo for transfer was generally good, although not optimal, even among experienced embryologists. WHAT IS KNOWN ALREADY: Previous research on the morphological assessment of early stage (two pronuclei to Day 3) embryos has shown varying levels of inter-observer and intra-observer agreement. However, single blastocyst transfer is now becoming increasingly popular and there are no published data that assess inter-observer and intra-observer agreement when selecting a single embryo for Day 5 transfer. STUDY DESIGN, SIZE, DURATION: This was a prospective study involving 10 embryologists working at five different IVF clinics within a single organization between July 2013 and November 2015. PARTICIPANTS/MATERIALS, SETTING, METHODS: The top 10 embryologists were selected based on their yearly Quality Assurance Program scores for blastocyst grading and were asked to morphologically grade all Day 5 embryos and choose a single embryo for transfer in a survey of 100 cases using 2D images. A total of 1000 decisions were therefore assessed. For each case, Day 5 images were shown, followed by a Day 3 and Day 5 image of the same embryo. Subgroup analyses were also performed based on the following characteristics of embryologists: the level of clinical embryology experience in the laboratory; amount of research experience; number of days per week spent grading embryos. The agreement between these embryologists and the one that scored the embryos on the actual day of transfer was also evaluated. Inter-observer and intra-observer variability was assessed using the kappa coefficient to evaluate the extent of agreement. MAIN RESULTS AND THE ROLE OF CHANCE: This study showed that all 10 embryologists agreed on the embryo chosen for transfer in 50 out of 100 cases. In 93 out of 100 cases, at least 6 out of the 10 embryologists agreed. The inter-observer and intra-observer agreement among embryologists when selecting a single Day 5 embryo for transfer was generally good as assessed by the kappa scores (kappa = 0.734, 95% CI: 0.665-0.791 and 0.759, 95% CI: 0.622-0.833, respectively). The subgroup analyses did not substantially alter the inter-observer and intra-observer agreement among embryologists. The agreement when Day 3 images were included alongside Day 5 images of the same embryos resulted in a change of mind at least three times by each embryologist (on average for <10% of cases) and resulted in a small decrease in inter-observer and intra-observer agreement between embryologists (kappa = 0.676, 95% CI: 0.617-0.724 and 0.752, 95% CI: 0.656-808, respectively).The assessment of the inter-observer agreement with regard to morphological grading of Day 5 embryos showed only a fair-to-moderate agreement, which was observed across all subgroup analyses. The highest overall kappa coefficient was seen for the grading of the developmental stage of an embryo (0.513; 95% CI: 0.492-0.538). The findings were similar when the individual embryologists were compared with the embryologist who made the morphological assessments of the available embryos on the actual day of transfer. LIMITATIONS, REASONS FOR CAUTION: All embryologists had already completed their training and were working under one organization with similar policies between the five clinics. Therefore, the inter-observer agreement might not be as high between embryologists working in clinics with different policies or with different levels of training. WIDER IMPLICATIONS OF THE FINDINGS: The generally good, although not optimal uniformity between participating embryologists when selecting a Day 5 embryo for transfer, as well as, the surprisingly low agreement when morphologically grading Day 5 embryos could be improved, potentially resulting in increased pregnancy rates. Future studies need to be directed toward technologies that can help achieve this. STUDY FUNDING/COMPETING INTERESTS: None declared. TRIAL REGISTRATION NUMBER: Not applicable.

Anti-Müllerian hormone kinetics in pregnancy and post-partum: a systematic review.

The aim of this systematic review is to critically appraise the available evidence regarding the kinetics of anti-Müllerian hormone (AMH) during pregnancy and post-partum. A systematic literature search was conducted in MEDLINE, Embase, CENTRAL, Scopus and Web of Science on 14 December 2015, aiming to identify studies providing data on the serum concentration of AMH in women at various stages of gestation and post-partum. There was a total of 1719 participants across eight studies. Seven out of the eight studies reported a decline in serum AMH concentration with advancing gestational age. Further, all four of the studies that evaluated pre- and post-delivery AMH concentrations found that it increased in the post-partum period. This review demonstrated an association between reduced maternal serum AMH concentrations and advancing gestational age, with a subsequent post-partum increase in concentration. These findings suggest that AMH measurements in pregnant women, especially at later stages of pregnancy, should not be used to assess ovarian reserve. Additionally, further longitudinal research would be beneficial, to elucidate the pathophysiological mechanism through which this decline in serum AMH concentration is observed during pregnancy.

Does oocyte donation compared with autologous oocyte IVF pregnancies have a higher risk of preeclampsia?

The aim of this study was to evaluate whether pregnancies resulting from oocyte donation have a higher risk of preeclampsia compared with pregnancies after IVF using autologous oocytes. Propensity score matching on maternal age and parity was carried out on a one to one basis, and a total of 144 singleton pregnancies resulting in delivery beyond 22 gestational weeks, achieved by oocyte donation, were compared with 144 pregnancies achieved through IVF and intracytoplasmic sperm injection with the use of autologous oocytes. All pregnancies were achieved after fresh embryo transfer. Obstetric and neonatal outcomes were compared for each pregnancy. Singleton pregnancies after oocyte donation were associated with a significantly higher risk for preeclampsia (OR 2.4, CI 1.02 to 5.8; P = 0.046), as well as for pregnancy-induced hypertension (OR 5.3, CI 1.1 to 25.2; P = 0.036), and caesarean delivery (OR 2.3, CI 1.4 to 3.7; P = 0.001) compared with pregnancies using autologous oocytes.

What is the best predictor of severe ovarian hyperstimulation syndrome in IVF? A cohort study.

PURPOSE: The purpose of the present study is to study what is the best predictor of severe ovarian hyperstimulation syndrome (OHSS) in IVF. METHODS: This is a retrospective analysis of all consecutive IVF/intracytoplasmic injection cycles performed during a 5-year period (2009-2014) in a single university fertility centre. All fresh IVF cycles where ovarian stimulation was performed with gonadotrophins and GnRH agonists or antagonists and triggering of final oocyte maturation was induced with the administration of urinary or recombinant hCG were analyzed (2982 patients undergoing 5493 cycles). Because some patients contributed more than one cycle, the analysis of the data was performed with the use of generalized estimating equation (GEE). RESULTS: Severe OHSS was diagnosed in 20 cycles (0.36%, 95% CI 0.20-0.52). The number of follicles ≥10 mm on the day of triggering final oocyte maturation represents the best predictor of severe OHSS in IVF cycles. The cutoff in the number of follicles ≥10 mm with the best capacity to discriminate between women that will and will not develop severe OHSS was ≥15. CONCLUSION: The presence of more than 15 follicles ≥10 mm on the day of triggering final oocyte maturation represents the best predictor of severe OHSS in IVF cycles.

Blastocyst utilization rates after continuous culture in two commercial single-step media: a prospective randomized study with sibling oocytes.

PURPOSE: The aim of this study is to determine whether blastocyst utilization rates are different after continuous culture in two different commercial single-step media. METHODS: This is a paired randomized controlled trial with sibling oocytes conducted in infertility patients, aged ≤40 years with ≥10 oocytes retrieved assigned to blastocyst culture and transfer. Retrieved oocytes were randomly allocated to continuous culture in either Sage one-step medium (Origio) or Continuous Single Culture (CSC) medium (Irvine Scientific) without medium renewal up to day 5 post oocyte retrieval. Main outcome measure was the proportion of embryos suitable for clinical use (utilization rate). RESULTS: A total of 502 oocytes from 33 women were randomly allocated to continuous culture in either Sage one-step medium (n = 250) or CSC medium (n = 252). Fertilization was performed by either in vitro fertilization or intracytoplasmic sperm injection, and embryo transfers were performed on day 5. Two patients had all blastocysts frozen due to the occurrence of severe ovarian hyperstimulation syndrome. Fertilization and cleavage rates, as well as embryo quality on day 3, were similar in the two media. Blastocyst utilization rates (%, 95% CI) [55.4% (46.4-64.1) vs 54.7% (44.9-64.6), p = 0.717], blastocyst formation rates [53.6% (44.6-62.5) vs 51.9 (42.2-61.6), p = 0.755], and proportion of good quality blastocysts [36.8% (28.1-45.4) vs 36.1% (27.2-45.0), p = 0.850] were similar in Sage one-step and CSC media, respectively. CONCLUSIONS: Continuous culture of embryos in Sage one-step and CSC media is associated with similar blastocyst development and utilization rates. Both single-step media appear to provide adequate support during in vitro preimplantation embryo development. Whether these observations are also valid for other continuous single medium protocols remains to be determined. CLINICAL TRIAL REGISTRATION NUMBER: NCT02302638.

Basal serum progesterone and history of elevated progesterone on the day of hCG administration are significant predictors of late follicular progesterone elevation in GnRH antagonist IVF cycles.

STUDY QUESTION: Are there any baseline predictors of progesterone elevation (PE) on the day of human chorionic gonadotrophin (hCG) which are not associated with the intensity of ovarian stimulation in women undergoing in vitro fertilization (IVF) using follicle stimulating hormone (FSH) and gonadotrophin-releasing hormone (GnRH) antagonists? SUMMARY ANSWER: Basal (Day 2 of the menstrual cycle) serum progesterone concentration and history of PE are baseline variables that can predict the occurrence of PE on the day of hCG independently of the intensity of ovarian stimulation. WHAT IS KNOWN ALREADY: PE on the day of hCG is associated with the magnitude of the ovarian response to stimulation. For this reason, it has been hypothesized that milder ovarian stimulation might reduce the probability of PE. However, given the fact that the number of oocytes retrieved is associated with the probability of live birth, such a strategy should be considered only in patients that are at high risk of PE on the day of hCG. STUDY DESIGN, SIZE, DURATION: This is a retrospective analysis of a cohort of fresh IVF/ICSI cycles (n = 1702) performed in a single IVF centre during the period 2001-2015. PARTICIPANTS/MATERIALS, SETTING, METHODS: Patients in whom ovarian stimulation was performed with FSH and GnRH antagonists and with basal FSH <14.0 mIU/ml, progesterone (P) ≤1.6 ng/ml and estradiol (E2) ≤80 pg/ml on the same day (prior to the initiation of stimulation) were considered eligible. PE was defined as serum progesterone concentration >1.5 ng/ml. Pre-stimulation characteristics of patients and basal hormonal profile were assessed for their ability to predict the occurrence of PE after ovarian stimulation through generalized estimating equation univariable and multivariable regression analyses, controlling for the effect of ovarian stimulation. Furthermore, a secondary analysis in a subset of patients with multiple IVF cycles explored whether the occurrence of PE in one of the previous cycles included in this study is associated with a significantly higher occurrence of PE elevation in subsequent cycles. MAIN RESULTS AND THE ROLE OF CHANCE: Univariable regression analyses showed that female age (OR: 0.97; 95% CI: 0.94-0.99), basal FSH (OR: 0.85; 95% CI: 0.79-0.92) and basal P (OR: 4.20; 95% CI: 2.47-7.12) were baseline variables that could significantly predict PE on the day of hCG. When these variables were entered in the same model as covariates, only basal FSH (OR: 0.86; 95% CI: 0.80-0.94) and basal P (OR: 3.83; 95% CI: 2.24-6.56) could still predict the occurrence of PE. Basal P (OR: 6.30; 95% CI: 3.35-11.82) was the only variable that could significantly predict the occurrence of PE on the day of hCG after adjusting for the intensity of ovarian stimulation. The secondary analysis revealed that history of PE on the day of hCG in a previous cycle was also strongly associated with an increased risk of PE in a subsequent cycle. LIMITATIONS, REASONS FOR CAUTION: This is a retrospective analysis and although the effect of the most important confounders was controlled for in the multivariable analysis, the presence of residual bias cannot be excluded. WIDER IMPLICATIONS OF THE FINDINGS: The findings of this study might help clinicians identify patients at high risk for late follicular PE and alter the management of their cycle. STUDY FUNDING/COMPETING INTERESTS: None. TRIAL REGISTRATION NUMBER: Not applicable.

Estimating the net effect of progesterone elevation on the day of hCG on live birth rates after IVF: a cohort analysis of 3296 IVF cycles.

STUDY QUESTION: What is the proper way of assessing the effect of progesterone elevation (PE) on the day of hCG on live birth in women undergoing fresh embryo transfer after in vitro fertilization (IVF) using GnRH analogues and gonadotrophins? SUMMARY ANSWER: This study indicates that a multivariable approach, where the effect of the most important confounders is controlled for, can lead to markedly different results regarding the association between PE on the day of hCG and live birth rates after IVF when compared with the bivariate analysis that has been typically used in the relevant literature up to date. WHAT IS KNOWN ALREADY: PE on the day of hCG is associated with decreased pregnancy rates in fresh IVF cycles. Evidence for this comes from observational studies that mostly failed to control for potential confounders. STUDY DESIGN, SIZE, DURATION: This is a retrospective analysis of a cohort of fresh IVF/intracytoplasmic sperm injection cycles (n = 3296) performed in a single IVF centre during the period 2001-2013. PARTICIPANTS/MATERIALS, SETTING, METHODS: Patients in whom ovarian stimulation was performed with gonadotrophins and GnRH analogues. Natural cycles and cycles where stimulation involved the administration of clomiphene were excluded. In order to reflect routine clinical practice, no other exclusion criteria were imposed on this dataset. The primary outcome measure for this study was live birth defined as the delivery of a live infant after 24 weeks of gestation. We compared the association between PE on the day of hCG (defined as P > 1.5 ng/ml) and live birth rates calculated by simple bivariate analyses with that derived from multivariable logistic regression. The multivariable analysis controlled for female age, number of oocytes retrieved, number of embryos transferred, developmental stage of embryos at transfer (cleavage versus blastocyst), whether at least one good-quality embryo was transferred, the woman's body mass index, the total dose of FSH administered during ovarian stimulation and the type of GnRH analogues used (agonists versus antagonists) during ovarian stimulation. In addition, an interaction analysis was performed in order to assess whether the ovarian response (<6, 6-18, >18 oocytes) has a moderating effect on the association of PE on the day of hCG with live birth rates after IVF. MAIN RESULTS AND THE ROLE OF CHANCE: Live birth rates were not significantly different between cycles with and those without PE when a bivariate analysis was performed [odds ratio (OR): 0.78, 95% confidence interval (CI): 0.56-1.09]. However, when a multivariable analysis was performed, controlling for the effect of the aforementioned confounders, live birth rates (OR: 0.68, 95% CI: 0.48-0.97) were significantly decreased in the group with PE on the day of hCG. The number of oocytes retrieved was the most potent confounder, causing a 29.4% reduction in the OR for live birth between the two groups compared. Furthermore, a moderating effect of ovarian response on the association between PE and live birth rates was not supported in the present analysis since no interaction was detected between PE and the type of ovarian response (<6, 6-18, >18 oocytes). LIMITATIONS, REASONS FOR CAUTION: This is a retrospective analysis of data collected during a 12-year period, and although the effect of the most important confounders was controlled for in the multivariable analysis, the presence of residual bias cannot be excluded. WIDER IMPLICATIONS OF THE FINDINGS: This analysis highlights the need for a multivariable approach when researchers or clinicians aim to evaluate the impact of PE on pregnancy rates in their own clinical setting. Failure to do so might explain why many past studies have failed to identify the detrimental effect of PE in fresh IVF cycles. STUDY FUNDING/COMPETING INTERESTS: None.

Live birth rates after modified natural cycle compared with high-dose FSH stimulation using GnRH antagonists in poor responders.

STUDY QUESTION: Do live birth rates differ between modified natural cycles (MNCs) and cycles using high-dose follicle stimulating hormone (HDFSH) with gonadotrophin-releasing hormone (GnRH) antagonist in poor responder patients? SUMMARY ANSWER: Live birth rates are significantly higher in MNC compared with HDFSH GnRH antagonist cycles in poor responder patients. WHAT IS KNOWN ALREADY: Previous data on the efficiency of MNC in poor responders are very limited and suggest that MNC in vitro fertilization (IVF) does not offer a realistic solution for parenthood in these patients, since live birth rates are disappointingly low. To date, no studies exist comparing MNC with HDFSH stimulation protocols in poor responders. STUDY DESIGN, SIZE, DURATION: The present retrospective study included 161 MNCs (106 women in the MNC group) and 164 HDFSH antagonist cycles (136 women in the HDFSH group) performed between January 2008 and December 2013 at Eugonia Assisted Reproduction Unit. The patients included in the study had to fulfill the Bologna criteria for the definition of poor ovarian response. PARTICIPANTS/MATERIALS, SETTING, METHODS: Irrespective of their age, poor responder patients should have a diminished ovarian reserve as shown by low antral follicle count (≤5) and increased basal FSH (>12 IU/l), and one or more previous failed IVF cycles in which ≤3 oocytes were retrieved using a high gonadotrophin dose. Analysis was performed by adjusting for the non-independence of the data. MAIN RESULTS AND THE ROLE OF CHANCE: The probability of live birth was significantly higher in the MNC when compared with the HDFSH group (OR: 4.01, 95% CI: 1.14-14.09), after adjusting for basal FSH, female age and cause of infertility, variables which were shown to be associated with the probability of live birth in univariable analysis. MNCs were characterized by significantly lower total gonadotrophin dose (490.0 ± 35.2 IU versus 2826.1 ± 93.4 IU, P < 0.001), lower estradiol concentrations (237.5 ± 12.3 pg/ml versus 487.3 ± 29.8 pg/ml, P < 0.001), fewer follicles present on the day of hCG (1.9 ± 0.1 versus 3.2 ± 0.2, P < 0.001), fewer oocytes retrieved (1.1 ± 0.01 versus 2.4 ± 0.1, P < 0.001), fewer oocytes fertilized (0.7 ± 0.1 versus 1.4 ± 0.1, P < 0.001), fewer embryos transferred (0.7 ± 0.1 versus 1.4 ± 0.1, P < 0.001), fewer good-quality embryos available (0.5 ± 0.1 versus 0.8 ± 0.1, P < 0.001) and fewer good-quality embryos transferred (0.5 ± 0.05 versus 0.8 ± 0.1, P < 0.001) compared with the HDFSH group. However, the proportion of cycles with at least one good-quality embryo transferred per started cycle was similar between the two groups compared (62.5, 95% CI: 52.7-72.3 versus 62.7, 95% CI: 53.0-72.5, respectively). LIMITATIONS, REASONS FOR CAUTION: This is a retrospective comparison between MNC and HDFSH GnRH antagonist protocols in a large group of poor responder patients according to the Bologna criteria. Although the two groups compared were not imbalanced for all basic characteristics and multivariate analysis were performed to adjust for all known confounders, it cannot be excluded that non-apparent sources of bias might still be present. Future randomized controlled trials are necessary to verify the present findings. WIDER IMPLICATIONS OF THE FINDINGS: Both MNC and HDFSH antagonist protocols offer very low chances of live birth in poor responder patients who fulfill the Bologna criteria. However, MNC-IVF is a more patient-friendly approach, with a higher probability of live birth compared with the HDFSH antagonist protocol. In this respect, the current data might be of help in counseling such patients, who do not wish to undergo oocyte donation, prior to abandoning treatment altogether and/or proceeding to adoption. STUDY FUNDING/COMPETING INTERESTS: No funding was obtained. C.A.V. reports personal fees and non-financial support from Merck, Sharp and Dome, personal fees and non-financial support from Merck Serono, personal fees and non-financial support from IPSEN Hellas S.A. outside the submitted work. B.C.T. reports grants from Merck Serono, grants from Merck Sharp & Dohme, personal fees from IBSA, personal fees from Merck Sharp & Dohme and personal fees from Ovascience outside the submitted work .