Progesterone therapy for prevention of recurrent spontaneous preterm birth in a minority patient population: a retrospective study.

BACKGROUND: Preterm birth is a leading cause of infant morbidity and mortality worldwide. The burden of prematurity underscores the need for effective risk reduction strategies. The purpose of this study is to evaluate the efficacy of progesterone therapy, both intramuscular 17-α-hydroxyprogesterone caproate (IM 17-OHPC) and vaginal progesterone, in the prevention of recurrent spontaneous preterm birth (sPTB). The co-primary outcomes included: recurrent spontaneous PTB < 37 and < 34 weeks' gestation. METHODS: This retrospective cohort study included 637 pregnant patients that delivered at any of the three hospitals within the Los Angeles County healthcare system between October 2015 and June 2021. We compared frequencies of measured variables between each of the progesterone treated groups to no treatment using Pearson chi-squared tests and independent t-tests for categorical and continuous variables, respectively. We estimated crude and adjusted associations between each specific treatment (versus no treatment) and primary outcomes using logistic regression. RESULTS: Recurrent sPTB < 37 weeks' gestation occurred in 22.3% (n = 64) of those in the no treatment group, 29.1% (n = 86, p = .077) in the 17-OHPC group, and 14.3% (n = 6, p = 0.325) in the vaginal progesterone group. Recurrent sPTB < 34 weeks' gestation was 6.6% (n = 19) in the no treatment group, 11.8% (n = 35, p = .043) in the 17-OHPC group, and 7.1% (n = 3, p = 1) in the vaginal progesterone group. Among all participants, neither 17-OHPC nor vaginal progesterone was significantly associated with a reduction in recurrent sPTB at any time point. Among those with a short cervix, IM 17-OHPC was positively associated with recurrent sPTB < 37 weeks' gestation (aOR 5.61; 95% CI 1.16, 42.9). CONCLUSIONS: Progesterone therapy of any type did not reduce the risk of recurrent sPTB < 34 or < 37 weeks' gestation compared to no progesterone therapy.

Reassessing Preterm Birth Prevention After the Withdrawal of 17-α Hydroxyprogesterone Caproate.

The U.S. Food and Drug Administration has recently withdrawn approval for 17-α hydroxyprogesterone caproate for prevention of recurrent preterm birth, and recent studies have called into question benefits of the pessary in the setting of a short cervix. Obstetric health care professionals are once again left with limited remaining options for preterm birth prevention. This narrative review summarizes the best current evidence on the use of vaginal progesterone, low-dose aspirin, and cerclage for the prevention of preterm birth; attempts to distill possible lessons learned from studies of progesterone and pessary, as well as their implementation into practice; and highlights areas where inroads into preterm birth prevention may be possible outside of the progesterone-aspirin-cerclage paradigm.

Addressing a broken drug pipeline for preterm birth: why early preterm birth is an orphan disease.

Preterm birth remains one of the most urgent unresolved medical problems in obstetrics, yet only 2 therapeutics for preventing preterm birth have ever been approved by the United States Food and Drug Administration, and neither remains on the market. The recent withdrawal of 17-hydroxyprogesterone caproate (17-OHPC, Makena) marks a new but familiar era for obstetrics with no Food and Drug Administration-approved pharmaceuticals to address preterm birth. The lack of pharmaceuticals reflects a broad and ineffective pipeline hindered by extensive regulatory hurdles, soaring costs of performing drug research, and concerns regarding adverse effects among a particularly vulnerable population. The pharmaceutical industry has historically limited investments in research for diseases with similarly small markets, such as cystic fibrosis, given their rarity and diminished projected financial return. The Orphan Drug Act, however, incentivizes drug development for "orphan diseases", defined as affecting <200,000 people in the United States annually. Although the total number of preterm births in the United States exceeds this threshold annually, the early subset of preterm birth (<34 weeks' gestation) would qualify, which is predominantly caused by inflammation and infection. The scientific rationale for classifying preterm birth into early and late subsets is strong given that their etiologies differ, and therapeutics that may be efficacious for one subset may not work for the other. For example, antiinflammatory therapeutics would be expected to be highly effective for early but not late preterm birth. A robust therapeutic pipeline of antiinflammatory drugs already exists, which could be used to target spontaneous early preterm birth, in combination with antibiotics shown to sterilize the amniotic cavity. New applications for therapeutics targeting spontaneous early preterm birth could categorize as orphan disease drugs, which could revitalize the preterm birth therapeutic pipeline. Herein, we describe why drugs targeting early preterm birth should qualify for orphan status, which may increase pharmaceutical interest for this vitally important obstetrical condition.

Effect of formulation and route of administration on the distribution of 17-hydroxyprogesterone caproate in rats.

Weekly intramuscular (250 mg/week) or subcutaneous (275 mg/week) injections of 17-hydroxyprogesterone caproate (17-OHPC) is the only treatment option for the prevention of preterm birth in women with a prior history of preterm delivery.The objective of the current study was to determine the relative distribution of 17-OHPC in selected tissues in adult female SD rats after IM (oily formulation or solution), IV (solution), PO (solution), or intravaginal (suppository) administration.Plasma, uterus, adipose, and liver samples were collected at various times and analysed by LC-MS-MS.The highest concentrations of 17-OHPC were observed in the adipose tissue, after IM (oily formulation), and intravaginal administration.Substantial concentrations of 17-OHPC were also observed in the uterus after IM, intravaginal and IV administration.17-OHPC was not detected in the liver and in any of the tissues tested after PO administration.17-OHPC levels in plasma after intravaginal suppository administration were low despite substantial concentrations in the adipose and the uterus.The distribution of 17-OHPC depends on the formulation, the route of administration, and the sampling time.Low systemic concentrations and substantial distribution in the tissues of interest after intravaginal administration warrants future studies to evaluate the potential of the daily intravaginal route of administration of 17-OHPC.

Effect of 17-Hydroxyprogesterone Caproate on Interleukin-6 and Tumor necrosis factor-alpha in expectantly managed early-onset preeclampsia.

The study aimed to evaluate the effect of 17 hydroxy progesterone (17-OHPC) on interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in expectantly managed early-onset preeclampsia (PE). A randomized open-label controlled study included women who were diagnosed as early-onset PE if they assigned to expectant management according to the American College of Obstetricians and Gynecologists (ACOG) 2013 criteria for diagnosis of severity of PE. Patients were randomized into Group A (40 patients) received 17-OHPC 250 mg intra-muscular at admission and every 7 days thereafter and Group B (40 patients) was given the usual conservative measures of early-onset PE as a control group. Blood samples were obtained from all participants for measurements of TNF-α and IL-6 levels at admission and repeated at termination of pregnancy. The primary outcome was the mean difference between TNF-α and IL-6 levels before and after treatment in both groups. TNF-α and IL-6 levels at admission were not different between the two groups. However, there was a significant difference concerning these inflammatory biomarkers within the same group at admission and at termination (p < 0.001), with significant decline of IL-6 and TNF-α level in the 17-OHPC treated group and significant rise of IL-6 and TNF-α in the control group. There was a strong positive correlation between systolic blood pressure (SBP) at admission and TNF-α level (r= 0.867, p=0.017), and moderately positive significant correlation between diastolic blood pressure (DBP) at admission and TNF-α (r=0.610, p < 0.001). There was a mild positive significant correlation between IL-6 levels and SBP (r= 0.231, p=0.039), and DBP (r= 0.203, p= 0.041) at admission. In conclusion, 17-OHPC has no effect in improving maternal or neonatal outcomes in conservatively managed early onset PE, although it alters the inflammatory markers levels (IL-6 and TNF-α) that could improve the pathogenesis of PE.

Relationship between plasma concentration of 17-hydroxyprogesterone caproate and gestational age at preterm delivery.

BACKGROUND: The effectiveness of 17-hydroxyprogesterone caproate is unclear as trials have provided conflicting results. With the absence of fundamental pharmacologic studies addressing dosing or the relationship between drug concentration and gestational age at delivery, the effectiveness of the medication cannot be evaluated. OBJECTIVE: This study aimed to evaluate the relationship between plasma concentrations of 17-hydroxyprogesterone caproate and preterm birth rates and gestational age at preterm delivery and to assess the safety of the 500-mg dose. STUDY DESIGN: This study recruited 2 cohorts with previous spontaneous preterm birth; 1 cohort (n=143) was randomly assigned to either 250-mg or 500-mg 17-hydroxyprogesterone caproate, and the other cohort (n=16) was receiving the 250-mg dose for routine care. Steady-state trough plasma concentrations of 17-hydroxyprogesterone caproate obtained at 26 to 30 weeks of gestation were correlated to dose, spontaneous preterm birth rates, and measures of gestational length. Furthermore, maternal and neonatal safety outcomes were evaluated according to dose. RESULTS: There was a dose proportional increase in trough plasma concentrations with the 250-mg (median, 8.6 ng/m; n=66) and 500-mg (median, 16.2 ng/mL; n=55) doses. In 116 compliant participants with blood samples, drug concentration was not related to the spontaneous preterm birth rate (odds ratio, 1.00; 95% confidence interval, 0.93-1.08). However, there was a significant relationship between drug concentration and both the interval from the first administration to delivery (interval A: coefficient, 1.11; 95% confidence interval, 0.00-2.23; P=.05) and the interval from the 26- to 30-week blood draw to delivery (interval B: coefficient, 1.56; 95% confidence interval, 0.25-2.87; P=.02). The spontaneous preterm birth rate or measures of gestational length were not related to dose. Postenrollment cerclage adversely affected all pharmacodynamic assessments because it was a powerful predictor of spontaneous preterm birth (odds ratio, 4.03; 95% confidence interval, 1.24-13.19; P=.021) and both measures of gestational length (interval A [coefficient, -14.9; 95% confidence interval, -26.3 to -3.4; P=.011] and interval B [coefficient, -15.9; 95% confidence interval, -25.8 to -5.9; P=.002]). Initial cervical length was significantly related to the risk of postenrollment cerclage (odds ratio, 0.80; 95% confidence interval, 0.70-0.92; P=.001). Maternal and neonatal safety outcomes were similar in both dosing groups. CONCLUSION: In this pharmacodynamic study, trough plasma 17-hydroxyprogesterone caproate concentrations were significantly associated with gestational age at preterm birth but not with the preterm birth rate. Postenrollment cerclage was a powerful predictor of spontaneous preterm birth rate and gestational length. Initial cervical length predicted the risk of postenrollment cerclage. Adverse events were similar with the 500-mg and 250-mg doses of 17-hydroxyprogesterone caproate.

Vaginal Progesterone Is Associated with Intrahepatic Cholestasis of Pregnancy.

OBJECTIVE: The frequency of intrahepatic cholestasis of pregnancy (ICP) peaks during the third trimester of pregnancy when plasma progesterone levels are the highest. Furthermore, twin pregnancies are characterized by higher progesterone levels than singletons and have a higher frequency of cholestasis. Therefore, we hypothesized that exogenous progestogens administered for reducing the risk of spontaneous preterm birth may increase the risk of cholestasis. Utilizing the large IBM MarketScan Commercial Claims and Encounters Database, we investigated the frequency of cholestasis in patients treated with vaginal progesterone or intramuscular 17α-hydroxyprogesterone caproate for the prevention of preterm birth. STUDY DESIGN: We identified 1,776,092 live-born singleton pregnancies between 2010 and 2014. We confirmed second and third trimester administration of progestogens by cross-referencing the dates of progesterone prescriptions with the dates of scheduled pregnancy events such as nuchal translucency scan, fetal anatomy scan, glucose challenge test, and Tdap vaccination. We excluded pregnancies with missing data regarding timing of scheduled pregnancy events or progesterone treatment prescribed only during the first trimester. Cholestasis of pregnancy was identified based on prescriptions for ursodeoxycholic acid. We used multivariable logistic regression to estimate adjusted (for maternal age) odds ratios for cholestasis in patients treated with vaginal progesterone, and in patients treated with 17α-hydroxyprogesterone caproate compared with those not treated with any type of progestogen (the reference group). RESULTS: The final cohort consisted of 870,599 pregnancies. Among patients treated with vaginal progesterone during the second and third trimester, the frequency of cholestasis was significantly higher than the reference group (0.75 vs. 0.23%, adjusted odds ratio [aOR]: 3.16, 95% confidence interval [CI]: 2.23-4.49). In contrast, there was no significant association between 17α-hydroxyprogesterone caproate and cholestasis (0.27%, aOR: 1.12, 95% CI: 0.58-2.16) CONCLUSION: Using a robust dataset, we observed that vaginal progesterone but not intramuscular 17α-hydroxyprogesterone caproate was associated with an increased risk for ICP. KEY POINTS: · Previous studies have been underpowered to detect potential association between progesterone and ICP.. · Vaginal progesterone was significantly associated with ICP.. · Intramuscular 17α-hydroxyprogesterone was not associated with ICP..

Society for Maternal-Fetal Medicine Statement: Response to the Food and Drug Administration's withdrawal of 17-alpha hydroxyprogesterone caproate.

On April 5, 2023, the US Food and Drug Administration withdrew the approval of 17-alpha hydroxyprogesterone caproate, effective immediately, because of the lack of evidence that it reduces the risk of recurrent spontaneous preterm birth. This decision withdraws approval for all formulations of 17-alpha hydroxyprogesterone caproate (both intramuscular and subcutaneous) and applies to both brand name (Makena) and generic versions of the medication. We agree with the Food and Drug Administration determination and discourage continued prescribing of 17-alpha hydroxyprogesterone caproate, including through compounding pharmacies. We do not recommend changing indications for cerclage, indications for vaginal progesterone in patients with a short cervix, or recommendations against activity restriction based on the Food and Drug Administration withdrawal of 17-alpha hydroxyprogesterone caproate from the market. We recommend that discussion of the use of vaginal progesterone for primary prevention of recurrent preterm birth without input of cervical length or in those with a cervical length of ≥25 mm includes a shared decision-making process, especially if a progesterone formulation for preterm birth prevention was received in a previous pregnancy. The Food and Drug Administration determined that it would be inappropriate to delay the effective date of the withdrawal to allow patients currently receiving 17-alpha hydroxyprogesterone caproate to finish treatment. We agree with the Food and Drug Administration that there is no evidence of benefit with continued treatment. Patients currently receiving 17-alpha hydroxyprogesterone caproate can be counseled that the Food and Drug Administration's Center for Drug Evaluation and Research has not identified evidence of harm from discontinuation before 37 weeks of gestation.

Obstetric Indications for Progestin Therapy.

Specifically, meta-analyses of randomized trials demonstrate that vaginal progesterone reduces the risk of preterm birth in selected high-risk singleton pregnancies. 17-OHPC may also reduce the risk of recurrent preterm birth in singletons. Finally, one trial suggests that vaginal progesterone may also be beneficial in improving live birth rates in singletons with prior miscarriages and early pregnancy bleeding.

A Possible Mechanism of Action of 17α-Hydroxyprogesterone Caproate: Enhanced IL-10 Production.

OBJECTIVE: The rate of recurrent spontaneous preterm birth (PTB) was reduced by 33% in the Maternal-Fetal Medicine Unit (MFMU) Network trial of 17α-hydroxyprogesterone caproate (17-OHPC), but the mechanism of action, 17 years later, remains elusive. The robustness of the interleukin-10 (IL-10) response to lipopolysaccharide (LPS) stimulation of leukocytes in pregnant women with a prior PTB correlates with gestational age at delivery. This study sought to determine if there is a relationship between the concentration of 17-OHPC and response to LPS stimulation. STUDY DESIGN: We performed a secondary analysis of data from the Omega-3 MFMU trial which evaluated the effectiveness of omega-3 fatty acid supplementation in reducing recurrent PTB. We utilized previously characterized data from a subanalyses of the Omega-3 trial of IL-10 and tumor necrosis factor alpha (TNF-α) levels from peripheral blood mononuclear cells stimulated with LPS. Blood was obtained from enrolled women at 16 to 22 weeks' gestation (baseline) and 25 to 28 weeks' gestation (posttreatment). All women received 17-OHPC and plasma 17-OHPC concentrations were measured at 25 to 28 weeks' gestation. We analyzed these data to determine if there was a relationship between 17-OHPC concentration and cytokine production. We then performed an in vitro study to determine if 17-OHPC could directly alter cytokine production by THP-1-derived macrophages. RESULTS: In the clinical samples, we found that 17-OHPC plasma concentrations were correlated with the quantity of the LPS-stimulated production of IL-10. TNF-α production after LPS stimulation was unrelated to 17-OHPC concentration. In the in vitro study, we demonstrate a 17-OHPC concentration dependent increase in IL-10 production. CONCLUSION: In women receiving 17-OHPC for PTB prevention, we demonstrate a relationship between plasma 17-OHPC and LPS-stimulated IL-10 production by circulating leukocytes. We also demonstrate that, in vitro, 17-OHPC treatment affects IL-10 production by LPS-stimulated macrophages. Collectively, these findings support an immunomodulatory mechanism of action of 17-OHPC in the prevention of recurrent PTB. KEY POINTS: · 17-OHPC plasma concentrations and LPS-stimulated IL-10 levels correlate in clinical samples in women at risk for recurrent preterm birth.. · 17-OHPC can modulate the response of LPS-stimulated macrophages to increase IL-10 production.. · There was no relationship between TNF-α and plasma concentration of 17-OHPC in clinical samples or in vitro..

Eligibility, Utilization, and Effectiveness of 17-Alpha Hydroxyprogesterone Caproate in a Statewide Population-Based Cohort of Medicaid Enrollees.

OBJECTIVE: The primary objective was to estimate the initiation and adherence rates of 17 α-hydroxyprogesterone caproate (17OHPC) among eligible mothers in a statewide population-based cohort of Medicaid enrollees. The secondary objectives were to (1) determine the association of maternal sociodemographic and clinical characteristics with 17OHPC utilization and (2) assess the real-world effectiveness of 17OHPC on recurrent preterm birth prevention and admission to neonatal intensive care unit (NICU). STUDY DESIGN: This is a retrospective cohort study using a linked, longitudinal administrative dataset of birth certificates and medical assistance claims. Medicaid-enrolled mothers in Pennsylvania were included in this study if they had at least one singleton live birth from 2014 to 2016 following at least one spontaneous preterm birth. Maternal Medicaid claims were used to ascertain the use of 17OHPC from various manufacturers, including compounded formulations. Propensity score matching was used to create a covariate balance between 17OHPC treatment and comparison groups. RESULTS: We identified 4,781 Medicaid-covered 17OHPC-eligible pregnancies from 2014 to 2016 in Pennsylvania, 3.4% of all Medicaid-covered singleton live births. The population-based initiation rate was 28.5% among eligible pregnancies. Among initiators, 50% received ≥16 doses as recommended, while 10% received a single dose only. The severity of previous spontaneous preterm birth was the strongest predictor for the initiation and adherence of 17OHPC. In the matched treatment (n = 1,210) and comparison groups (n = 1,210), we found no evidence of 17OHPC effectiveness. The risks of recurrent preterm birth (relative risk [RR] 1.10, 95% confidence interval [CI] 0.97-1.24) and births admitted to NICU (RR 1.00, 95% CI 0.84-1.18) were similar in treated and comparison mothers. CONCLUSION: The 17OHPC-eligible population represented 3.4% of singleton live births. Less than one-third of eligible mothers initiated treatment. Among initiators, 50% were treatment adherent. We found no difference in the risk of recurrent preterm birth or admission to NICU between treatment and comparison groups. KEY POINTS: · About 3.4% of singleton live births were eligible for 17OHPC.. · About 30% of eligible mothers initiated treatment.. · We found no association of 17OHPC with recurrent preterm birth..

A Comparison of Vaginal and Intramuscular Progesterone for the Prevention of Recurrent Preterm Birth.

OBJECTIVE: This study aimed to examine whether vaginal progesterone is noninferior to 17-α hydroxyprogesterone caproate (17OHP-C) in the prevention of recurrent preterm birth (PTB). STUDY DESIGN: This retrospective cohort study included singleton pregnancies among women with a history of spontaneous PTB who received prenatal care at a single tertiary center from 2011 to 2016. Pregnancies were excluded if progesterone was not initiated prior to 24 weeks or the fetus had a major congenital anomaly. The primary outcome was PTB <37 weeks. A priori, noninferiority was to be established if the upper bound of the adjusted two-sided 90% confidence interval (CI) for the difference in PTB fell below 9%. Inverse probability of treatment weighting (IPTW) was used to carefully control for confounding associated with choice of treatment and PTB. Adjusted differences in PTB proportions were estimated via IPTW regression, with standard errors adjustment for multiple pregnancies per woman. Secondary outcomes included PTB <34 and <28 weeks, spontaneous PTB, neonatal intensive care unit admission, and gestational age at delivery. RESULTS: Among 858 pregnancies, 41% (n = 353) received vaginal progesterone and 59% (n = 505) were given 17OHP-C. Vaginal progesterone use was more common later in the study period, and among women who established prenatal care later, had prior PTBs at later gestational ages, and whose race/ethnicity was neither non-Hispanic white nor non-Hispanic Black. Vaginal progesterone did not meet noninferiority criteria compared with 17-OHPC in examining PTB <37 weeks, with an IPTW adjusted difference of 3.4% (90% CI: -3.5, 10.3). For secondary outcomes, IPTW adjusted differences between treatment groups were generally small and CIs were wide. CONCLUSION: We could not conclude noninferiority of vaginal progesterone to 17OHP-C; however, women and providers may be willing to accept a larger difference (>9%) when considering the cost and availability of vaginal progesterone versus 17OHP-C. A well-designed randomized trial is needed. KEY POINTS: · Vaginal progesterone is not noninferior to 17OHP-C.. · PTB risk may be 10% higher with vaginal progesterone.. · Associations did not differ based on obesity status..

The FDA Struggle to Withdraw Makena: Problems With the Accelerated Approval Process.

This Viewpoint discusses the controversy surrounding the FDA's efforts to withdraw Makena from the market and the broader implications for the accelerated approval pathway.

Effect of weekly 17-hydroxyprogesterone caproate on small for gestational age among pregnant women with HIV in Zambia.

The IPOP trial demonstrated a reduced risk of severe small for gestational age among infants born to women with HIV who received weekly intramuscular 17 alpha-hydroxyprogesterone caproate. This secondary analysis examined the 17P treatment effect in subgroups of maternal BMI, parity, timing of antiretroviral therapy (ART) initiation, and ART regimen. We found that 17P was more effective among nulliparous women, women who started ART before pregnancy, and those taking protease inhibitors.

Racial and ethnic representation in 17-hydroxyprogesterone caproate preterm birth prevention studies: a systematic review.

OBJECTIVES: The US preterm birth rate varies dramatically by race and ethnicity yet the racial and ethnic representation within studies evaluating 17-hydroxprogesterone caproate (17-P) for preterm birth prevention is unknown. The objectives of our study were to 1) examine the racial and ethnic representation of participants in 17-P preterm birth prevention studies, 2) evaluate adherence to the NIH race and ethnicity reporting guidelines and 3) compare racial and ethnic representation in research studies to national preterm birth incidence. METHODS: We systematically reviewed US studies published between January 2000 and December 2019. Study participant's race and ethnicity were reported using descriptive statistics then compared to US 2017//2018 preterm birth data using Pearson's chi-square. RESULTS: Eighteen studies met the inclusion criteria, 17 studies reported race, 11 studies reported ethnicity, and yet none of the studies followed the NIH criteria. Compared to 2017/2018 US preterm births, the proportion of black/African American study participants was significantly higher whereas the proportions of all other race categories were lower. CONCLUSIONS: More detailed reporting of race and ethnicity is needed in 17-P literature. Black women appear to be well represented while other racial and ethnic groups may be understudied.

Does the HCG trigger dose used for IVF impact luteal progesterone concentrations? a randomized controlled trial.

RESEARCH QUESTION: Is there an association between the ovulation trigger dose of human chorionic gonadotrophin (HCG) and endogenous progesterone production during the luteal phase? DESIGN: This randomized controlled four-arm study, at the Fertility Clinic, Odense University Hospital, Denmark, included women undergoing gonadotrophin-releasing hormone (GnRH) antagonist IVF treatment with ≤11 follicles ≥12 mm. Group 1-3 were triggered with 5000 IU, 6500 IU or 10,000 IU HCG, respectively, receiving 17α-hydroxyprogesterone caproate intramuscularly for luteal-phase support (LPS) to measure endogenous progesterone production. Group 4 received 6500 IU HCG trigger and vaginal progesterone. During the study, the 5000 IU and 10,000 IU HCG groups were switched from urinary to recombinant HCG, as urinary HCG was removed from market. Eight blood samples were drawn during the luteal phase. RESULTS: Ninety-four participants completed the study. There was a significant positive association between the HCG trigger dose and the progesterone at 8 days (P < 0.001), 10 days (P < 0.001) and 14 days (P < 0.001) post-oocyte retrieval. Comparing the groups individually revealed a significant difference in progesterone concentration between low and high trigger doses at 4 days (P = 0.037) and 8 days (P = 0.007) post-oocyte retrieval and between all intervention groups at oocyte retrieval + 6 days: group 1 and 2 (P = 0.011), group 2 and 3 (P = 0.042) and group 1 and 3 (P < 0.001). Higher HCG trigger dose increased the progesterone from the individual follicle. CONCLUSIONS: Increasing HCG trigger doses significantly increased endogenous progesterone concentration during the mid-late luteal phase.