Duration of progesterone-in-oil support after in vitro fertilization and embryo transfer: a randomized, controlled trial

Luteal phase support in assisted reproductive technology

Infertility affects one in six couples, with in vitro fertilization (IVF) offering many the chance of conception. Compared to the solitary oocyte produced during the natural menstrual cycle, the supraphysiological ovarian stimulation needed to produce multiple oocytes during IVF results in a dysfunctional luteal phase that can be insufficient to support implantation and maintain pregnancy. Consequently, hormonal supplementation with luteal phase support, principally exogenous progesterone, is used to optimize pregnancy rates; however, luteal phase support remains largely 'black-box' with insufficient clarity regarding the optimal timing, dosing, route and duration of treatment. Herein, we review the evidence on luteal phase support and highlight remaining uncertainties and future research directions. Specifically, we outline the physiological luteal phase, which is regulated by progesterone from the corpus luteum, and evaluate how it is altered by the supraphysiological ovarian stimulation used during IVF. Additionally, we describe the effects of the hormonal triggers used to mature oocytes on the degree of luteal phase support required. We explain the histological transformation of the endometrium during the luteal phase and evaluate markers of endometrial receptivity that attempt to identify the 'window of implantation'. We also cover progesterone receptor signalling, circulating progesterone levels associated with implantation, and the pharmacokinetics of available progesterone formulations to inform the design of luteal phase support regimens.

A 10-year follow-up on the practice of luteal phase support using worldwide web-based surveys

BACKGROUND

It has been demonstrated that luteal phase support (LPS) is crucial in filling the gap between the disappearance of exogenously administered hCG for ovulation triggering and the initiation of secretion of endogenous hCG from the implanting conceptus. LPS has a pivotal role of in establishing and maintaining in vitro fertilization (IVF) pregnancies. Over the last decade, a plethora of studies bringing new information on many aspects of LPS have been published. Due to lack of consent between researchers and a dearth of robust evidence-based guidelines, we wanted to make the leap from the bench to the bedside, what are the common LPS practices in fresh IVF cycles compared to current evidence and guidelines? How has expert opinion changed over 10 years in light of recent literature?

METHODS

Over a decade (2009-2019), we conducted 4 web-based surveys on a large IVF-specialist website on common LPS practices and controversies. The self-report, multiple-choice surveys quantified results by annual IVF cycles.

RESULTS

On average, 303 IVF units responded to each survey, representing, on average, 231,000 annual IVF cycles. Most respondents in 2019 initiated LPS on the day of, or the day after egg collection (48.7 % and 36.3 %, respectively). In 2018, 72 % of respondents administered LPS for 8-10 gestational weeks, while in 2019, 65 % continued LPS until 10-12 weeks. Vaginal progesterone is the predominant delivery route; its utilization rose from 64 % of cycles in 2009 to 74.1 % in 2019. Oral P use has remained negligible; a slight increase to 2.9 % in 2019 likely reflects dydrogesterone's introduction into practice. E2 and GnRH agonists are rarely used for LPS, as is hCG alone, limited by its associated risk of ovarian hyperstimulation syndrome (OHSS).

CONCLUSIONS

Our Assisted reproductive technology (ART)-community survey series gave us insights into physician views on using progesterone for LPS. Despite extensive research and numerous publications, evidence quality and recommendation levels are surprisingly low for most topics. Clinical guidelines use mostly low-quality evidence. There is no single accepted LPS protocol. Our study highlights the gaps between science and practice and the need for further LPS research, with an emphasis on treatment individualization.

When Can We Safely Stop Luteal Phase Support in Fresh IVF Cycles? A Literature Review

There is no consensus on the optimal duration of luteal phase support (LPS) in fresh IVF cycles. Although some clinicians withdraw LPS on the day of a positive pregnancy test, most clinicians continue its administration at least up to the 8th week of gestation. In this literature review, we included several randomized clinical trials comparing early and late cessation of LPS. Most studies have found no benefit in extended administration. These studies, however, were limited by their small sample size and selection bias. Until now, only a few attempts have been made to indicate when LPS can be safely stopped based on individual patient characteristics. In conclusion, the quality and quantity of the evidence regarding LPS duration in fresh IVF cycles is currently insufficient to justify early cessation in all patients. Individualization of LPS should receive high priority in future research.

Luteal Phase Support in IVF: Comparison Between Evidence-Based Medicine and Real-Life Practices

Background: Luteal phase support (LPS) in assisted reproduction cycles has been widely investigated in recent years. Although progesterone represents the preferential product for luteal phase supplementation in cycles with fresh embryo transfer, there is ongoing debate as to when to start, which is the best route, dosage and duration, and whether there is a place for additional agents. Nevertheless, fertility specialists do not always adhere to evidence-based recommendations in their clinical practice. The aim of this worldwide web-based survey is to document the currently used protocols for luteal phase support and appraisal tendencies of drug prescription behavior and to compare these to the existing evidence-based literature. Material and Methods: A questionnaire was developed and sent by secure e-mail to 1,480 clinicians involved in ART worldwide. One hundred and forty-eighth clinicians from 34 countries returned completed questionnaires. Results: Progesterone support is usually started on the day of oocyte retrieval. Eighty percent of clinicians applied the administration of vaginal progesterone only. Intramuscular progesterone was prescribed by 6%, while oral progestin or subcutaneous progesterone were each prescribed by 5% of clinicians, respectively. Progesterone was administered until 8-10 weeks' gestation by 35% and 12 weeks by 52% of respondents. Conclusions: Vaginal administration was the preferred route for luteal phase support. The reported emerging use of the oral route confirms the expected shift in clinical practice as a result of recent evidence showing a reassuring safety score of oral progestins. In spite of the lack of evidence supporting the continuation of luteal support until 12 weeks' gestation, this practice was adhered to by more than half of the clinicians surveyed, highlighting the difference between evidence-based medicine and real-life practices.

Short versus extended progesterone supplementation for luteal phase support in fresh IVF cycles: a systematic review and meta-analysis

This review and meta-analysis aim to assess the effect of prolonged progesterone support on pregnancy outcomes in women undergoing fresh embryo transfer after IVF/intracytoplasmic sperm injection (ICSI). Two independent authors searched Embase, MEDLINE and grey literature from inception to January 2019 for randomized controlled trials (RCT) of prolonged progesterone support versus early cessation. Risk of bias was assessed. Outcome measures were live birth, miscarriage and ongoing pregnancy rate. The study was registered with PROSPERO (CRD42018088605). Seven trials involving 1627 participants were included: three reported live birth rate (672/830), seven the miscarriage rate (178/1627) and seven the ongoing pregnancy rate (1351/1627). Clinical outcomes were similar between early progesterone cessation versus progesterone continuation: live birth rate (risk ratio [RR] 0.94, 95% confidence interval [CI] 0.88-1.00), miscarriage rate (RR 0.91, 95% CI 0.69-1.20) and ongoing pregnancy rate (RR 0.98, 95% CI 0.91-1.05). Ongoing pregnancy rates were similar when analyses were restricted to those with cessation of progesterone on the day of a positive human chorionic gonadotrophin (RR 0.93, 95% CI 0.83-1.06). This meta-analysis suggests that prolonged progesterone support may be unnecessary after fresh embryo transfer. Further larger RCT would be useful to corroborate and lead to standardized duration of progesterone luteal phase support across IVF/ICSI centres.

Evaluation of progestogen supplementation for luteal phase support in fresh in vitro fertilization cycles

OBJECTIVE

To evaluate the effectiveness of progestogen supplementation in improving clinical pregnancy rates in women undergoing fresh IVF cycles and to compare different routes, start times, durations, and estrogen coadministration regimen.

DESIGN

Comprehensive systematic review and meta-analysis.

SETTING

University.

PATIENT(S)

Women undergoing fresh IVF cycles who did and did not receive progestogen supplementation.

INTERVENTION(S)

Summary odds ratios (ORs) were calculated by binomial logistic regression.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy rates.

RESULT(S)

Eighty-two articles (26,726 women) were included. Clinical pregnancy rates were increased by IM (OR = 4.57), vaginal (OR = 3.34), SC (OR = 3.36), or oral (OR = 2.57) progestogen supplementation versus no treatment. The greatest benefit was observed when progestogens were supplemented IM versus vaginally (OR = 1.37). The optimal time to commence administration was between oocyte retrieval and ET (OR = 1.31), with oocyte retrieval +1 day being most beneficial. Coadministration of estrogen had no benefit (OR = 1.33), whether progestogens were coadministered vaginally or IM. Clinical pregnancy rates were equivalent when progestogen supplementation was ceased after ≤3 weeks or continued for up to 12 weeks (OR = 1.06).

CONCLUSION(S)

This broad-ranging meta-analysis highlights the need to reevaluate current clinical practice. The use of progestogens in fresh IVF cycles is substantially beneficial to clinical pregnancy. Critically, the use of IM progestogens should not be dismissed, as it yielded the greatest clinical pregnancy rates. Pregnancy success was impacted by initiation of therapy, with 1 day after oocyte retrieval being optimal. There is little evidence to support coadministration of estrogen or prolonging progestogen treatment beyond 3 weeks.

Luteal phase support for assisted reproduction cycles

BACKGROUND

Progesterone prepares the endometrium for pregnancy by stimulating proliferation in response to human chorionic gonadotropin(hCG) produced by the corpus luteum. This occurs in the luteal phase of the menstrual cycle. In assisted reproduction techniques(ART), progesterone and/or hCG levels are low, so the luteal phase is supported with progesterone, hCG or gonadotropin-releasing hormone (GnRH) agonists to improve implantation and pregnancy rates.

OBJECTIVES

To determine the relative effectiveness and safety of methods of luteal phase support provided to subfertile women undergoing assisted reproduction.

SEARCH METHODS

We searched databases including the Cochrane Menstrual Disorders and Subfertility Group (MDSG) Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, PsycINFO and trial registers. We conducted searches in November 2014, and further searches on 4 August 2015.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of luteal phase support using progesterone, hCG or GnRH agonist supplementation in ART cycles.

DATA COLLECTION AND ANALYSIS

Three review authors independently selected trials, extracted data and assessed risk of bias. We calculated odds ratios (ORs) and 95%confidence intervals (CIs) for each comparison and combined data when appropriate using a fixed-effect model. Our primary out come was live birth or ongoing pregnancy. The overall quality of the evidence was assessed using GRADE methods.

MAIN RESULTS

Ninety-four women RCTs (26,198 women) were included. Most studies had unclear or high risk of bias in most domains. The main limitations in the evidence were poor reporting of study methods and imprecision due to small sample sizes.1. hCG vs placebo/no treatment (five RCTs, 746 women)There was no evidence of differences between groups in live birth or ongoing pregnancy (OR 1.67, 95% CI 0.90 to 3.12, three RCTs,527 women, I2 = 24%, very low-quality evidence, but I2 of 61% was found for the subgroup of ongoing pregnancy) with a random effects model. hCG increased the risk of ovarian hyperstimulation syndrome (OHSS) (1 RCT, OR 4.28, 95% CI 1.91 to 9.6, low quality evidence).2. Progesterone vs placebo/no treatment (eight RCTs, 875 women)Evidence suggests a higher rate of live birth or ongoing pregnancy in the progesterone group (OR 1.77, 95% CI 1.09 to 2.86, five RCTs, 642 women, I2 = 35%, very low-quality evidence). OHSS was not reported.3. Progesterone vs hCG regimens (16 RCTs, 2162 women)hCG regimens included comparisons of progesterone versus hCG and progesterone versus progesterone + hCG. No evidence showed differences between groups in live birth or ongoing pregnancy (OR 0.95, 95% CI 0.65 to 1.38, five RCTs, 833 women, I2 = 0%, low quality evidence) or in the risk of OHSS (four RCTs, 615 women, progesterone vs hCG OR 0.54, 95% CI 0.22 to 1.34; four RCTs,678 women; progesterone vs progesterone plus hCG, OR 0.34, 95% CI 0.09 to 1.26, low-quality evidence).4. Progesterone vs progesterone with oestrogen (16 RCTs, 2577 women)No evidence was found of differences between groups in live birth or ongoing pregnancy (OR 1.12, 95% CI 0.91 to 1.38, nine RCTs,1651 women, I2 = 0%, low-quality evidence) or OHSS (OR 0.56, 95% CI 0.2 to 1.63, two RCTs, 461 women, I2 = 0%, low-quality evidence).5. Progesterone vs progesterone + GnRH agonist (seven RCTs, 1708 women)Live birth or ongoing pregnancy rates were lower in the progesterone-only group and increased in women who received progester one and one or more GnRH agonist doses (OR 0.62, 95% CI 0.48 to 0.81, nine RCTs, 2861 women, I2 = 55%, random effects, low quality evidence). Statistical heterogeneity for this comparison was high because of unexplained variation in the effect size, but the direction of effect was consistent across studies. OHSS was reported in one study only (OR 1.00, 95% CI 0.33 to 3.01, 1 RCT, 300 women, very low quality evidence).6. Progesterone regimens (45 RCTs, 13,814 women)The included studies reported nine different comparisons between progesterone regimens. Findings for live birth or ongoing pregnancy were as follows: intramuscular (IM) versus oral: OR 0.71, 95% CI 0.14 to 3.66 (one RCT, 40 women, very low-quality evidence);IM versus vaginal/rectal: OR 1.24, 95% CI 1.03 to 1.5 (seven RCTs, 2309 women, I2 = 71%, very low-quality evidence); vaginal/rectal versus oral: OR 1.19, 95% CI 0.83 to 1.69 (four RCTs, 857 women, I2 = 32%, low-quality evidence); low-dose versus high-dose vaginal: OR 0.97, 95% CI 0.84 to 1.11 (five RCTs, 3720 women, I2 = 0%, moderate-quality evidence); short versus long protocol:OR 1.04, 95% CI 0.79 to 1.36 (five RCTs, 1205 women, I2 = 0%, low-quality evidence); micronised versus synthetic: OR 0.9, 95%CI 0.53 to 1.55 (two RCTs, 470 women, I2 = 0%, low-quality evidence); vaginal ring versus gel: OR 1.09, 95% CI 0.88 to 1.36 (oneRCT, 1271 women, low-quality evidence); subcutaneous versus vaginal gel: OR 0.92, 95% CI 0.74 to 1.14 (two RCTs, 1465 women,I2 = 0%, low-quality evidence); and vaginal versus rectal: OR 1.28, 95% CI 0.64 to 2.54 (one RCT, 147 women, very low-quality evidence). OHSS rates were reported for only two of these comparisons: IM versus oral, and low versus high-dose vaginal. No evidence showed a difference between groups.7. Progesterone and oestrogen regimens (two RCTs, 1195 women)The included studies compared two different oestrogen protocols. No evidence was found to suggest differences in live birth or ongoing pregnancy rates between a short and a long protocol (OR 1.08, 95% CI 0.81 to 1.43, one RCT, 910 women, low-quality evidence) or between a low dose and a high dose of oestrogen (OR 0.65, 95% CI 0.37 to 1.13, one RCT, 285 women, very low-quality evidence).Neither study reported OHSS.

AUTHORS' CONCLUSIONS

Both progesterone and hCG during the luteal phase are associated with higher rates of live birth or ongoing pregnancy than placebo.The addition of GnRHa to progesterone is associated with an improvement in pregnancy outcomes. OHSS rates are increased with hCG compared to placebo (only study only). The addition of oestrogen does not seem to improve outcomes. The route of progester one administration is not associated with an improvement in outcomes.

Duration of luteal support after IVF is important, so why is there no consistency in practice? The results of a dynamic survey of practice in the United Kingdom

Luteal support is considered as an essential component of IVF treatment following ovarian stimulation and embryo transfer. Several studies have consistently demonstrated a benefit of luteal support compared with no treatment and whilst a number of preparations are available, no product has been demonstrated as superior. There is an emerging body of evidence which suggests that extension of luteal support beyond biochemical pregnancy does not confer a benefit in terms of successful pregnancy outcome. We performed two surveys separated by 5 years of practice evolution, with the latter reporting on the use of luteal support in all IVF clinics in the UK. All clinics reported utilising luteal support with the majority favouring the use of Cyclogest 400 mg twice daily. In contrast, there was no consensus on the optimal duration of luteal support. Whilst 24% of clinics withdrew luteal support at biochemical confirmation of pregnancy, 40% continued treatment until 12 weeks gestation. Several clinics even extended luteal support beyond 12 weeks gestation. We observed no difference in practice based on the size of the IVF unit or treatment funding source. Although there was some change in practice between surveys in many clinics, there was no uniformity in the direction of change.

Luteal insufficiency in first trimester

Luteal phase insufficiency is one of the reasons for implantation failure and has been responsible for miscarriages and unsuccessful assisted reproduction. Luteal phase defect is seen in women with polycystic ovaries, thyroid and prolactin disorder. Low progesterone environment is created iatrogenically due to interventions in assisted reproduction. Use of gonadotrophin-releasing hormone analogs to prevent the LH surge and aspiration of granulosa cells during the oocyte retrieval may impair the ability of corpus luteum to produce progesterone. Treatment of the underlying disorder and use of progestational agents like progesterone/human chorionic gonadotrophin have been found to be effective in women with a history of recurrent miscarriage. There has been no proved beneficial effect of using additional agents like ascorbic acid, estrogen, prednisolone along with progesterone. Despite their widespread use, further studies are required to establish the optimal treatment. Literature review and analysis of published studies on luteal phase support.

The optimal duration of progesterone supplementation in pregnant women after IVF/ICSI: a meta-analysis

can improve the rates of clinical pregnancy and live birth, but the optimal duration of treatment remains controversial. The objective of this meta-analysis was to investigate the effects of early progesterone cessation on pregnancy outcomes in women undergoing IVF/ICSI.

METHODS

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), the Chinese biomedicine (CBM) literature database, and the Wanfang database. The final search was performed in July 2012. All available randomised trials that compared the effects of early progesterone cessation with progesterone continuation during early pregnancy after IVF/ICSI were included. The main outcome measures were live birth rate, miscarriage rate and ongoing pregnancy rate. Fixed or random-effects models were chosen to calculate the risk ratio (RR).

RESULTS

Six eligible studies with a total of 1,201 randomised participants were included in the final analysis. No statistically significant differences were detected between patients who underwent early progesterone cessation and those who received progesterone continuation for luteal phase support in terms of live birth rate (RR: 0.95, 95% CI: 0.86-1.05), miscarriage rate (RR: 1.01, 95% CI: 0.74-1.38) or ongoing pregnancy rate (RR: 0.97, 95% CI: 0.90-1.05). These results did not change after a sensitivity analysis.

CONCLUSIONS

The currently available evidence suggests that progesterone supplementation beyond the first positive hCG test after IVF/ICSI might generally be unnecessary, although large-scale randomised controlled trials are needed to strengthen this conclusion.

Early progesterone cessation after in vitro fertilization/intracytoplasmic sperm injection: a randomized, controlled trial

OBJECTIVE

To investigate the effect of stopping progesterone (P) support at week 5 versus week 8 on ongoing pregnancy rate after in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI).

DESIGN

Prospective, randomized, controlled trial.

SETTING

University-affiliated infertility center.

PATIENT(S)

A total of 220 patients with intrauterine pregnancy demonstrated by transvaginal ultrasound after IVF/ICSI.

INTERVENTION(S)

Luteal phase support with micronized vaginal P was suspended at week 5 or at week 8.

MAIN OUTCOME MEASURE(S)

Ongoing pregnancy rate, miscarriage rate, and number of bleeding episodes.

RESULT(S)

Progesterone levels were similar on the day of the first pregnancy ultrasound exam (149 ± 108 vs. 167 ± 115 ng/mL). Significantly more bleeding episodes were observed in the first trimester in the group with early cessation of P supplementation (18.0 ± 2.6 vs. 7.2 ± 1.3 episodes). Miscarriage rates among singleton pregnancies were similar in the two groups (5/80 vs. 6/79).

CONCLUSION(S)

Vaginal P supplementation after IVF/ICSI can be safely withdrawn at 5 weeks' gestation, because cycle outcome was similar to conventional luteal phase support up to 8 weeks of pregnancy.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01177904.

Luteal phase support for assisted reproduction cycles

BACKGROUND

Progesterone prepares the endometrium for pregnancy by stimulating proliferation in response to human chorionic gonadotropin (hCG), which is produced by the corpus luteum. This occurs in the luteal phase of the menstrual cycle. In assisted reproduction techniques (ART) the progesterone or hCG levels, or both, are low and the natural process is insufficient, so the luteal phase is supported with either progesterone, hCG or gonadotropin releasing hormone (GnRH) agonists. Luteal phase support improves implantation rate and thus pregnancy rates but the ideal method is still unclear. This is an update of a Cochrane Review published in 2004 (Daya 2004).

OBJECTIVES

To determine the relative effectiveness and safety of methods of luteal phase support in subfertile women undergoing assisted reproductive technology.

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group (MDSG) Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, PsycINFO, CINAHL, Database of Abstracts of Reviews of Effects (DARE), LILACS, conference abstracts on the ISI Web of Knowledge, OpenSigle for grey literature from Europe, and ongoing clinical trials registered online. The final search was in February 2011.

SELECTION CRITERIA

Randomised controlled trials of luteal phase support in ART investigating progesterone, hCG or GnRH agonist supplementation in in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) cycles. Quasi-randomised trials and trials using frozen transfers or donor oocyte cycles were excluded.

DATA COLLECTION AND ANALYSIS

We extracted data per women and three review authors independently assessed risk of bias. We contacted the original authors when data were missing or the risk of bias was unclear. We entered all data in six different comparisons. We calculated the Peto odds ratio (Peto OR) for each comparison.

MAIN RESULTS

Sixty-nine studies with a total of 16,327 women were included. We assessed most of the studies as having an unclear risk of bias, which we interpreted as a high risk of bias. Because of the great number of different comparisons, the average number of included studies in a single comparison was only 1.5 for live birth and 6.1 for clinical pregnancy.Five studies (746 women) compared hCG versus placebo or no treatment. There was no evidence of a difference between hCG and placebo or no treatment except for ongoing pregnancy: Peto OR 1.75 (95% CI 1.09 to 2.81), suggesting a benefit from hCG. There was a significantly higher risk of ovarian hyperstimulation syndrome (OHSS) when hCG was used (Peto OR 3.62, 95% CI 1.85 to 7.06).There were eight studies (875 women) in the second comparison, progesterone versus placebo or no treatment. The results suggested a significant effect in favour of progesterone for the live birth rate (Peto OR 2.95, 95% CI 1.02 to 8.56) based on one study. For clinical pregnancy (CPR) the results also suggested a significant result in favour of progesterone (Peto OR 1.83, 95% CI 1.29 to 2.61) based on seven studies. For the other outcomes the results indicated no difference in effect.The third comparison (15 studies, 2117 women) investigated progesterone versus hCG regimens. The hCG regimens were subgrouped into comparisons of progesterone versus hCG and progesterone versus progesterone + hCG. The results did not indicate a difference of effect between the interventions, except for OHSS. Subgroup analysis of progesterone versus progesterone + hCG showed a significant benefit from progesterone (Peto OR 0.45, 95% CI 0.26 to 0.79).The fourth comparison (nine studies, 1571 women) compared progesterone versus progesterone + oestrogen. Outcomes were subgrouped by route of administration. The results for clinical pregnancy rate in the subgroup progesterone versus progesterone + transdermal oestrogen suggested a significant benefit from progesterone + oestrogen. There was no evidence of a difference in effect for other outcomes.Six studies (1646 women) investigated progesterone versus progesterone + GnRH agonist. We subgrouped the studies for single-dose GnRH agonist and multiple-dose GnRH agonist. For the live birth, clinical pregnancy and ongoing pregnancy rate the results suggested a significant effect in favour of progesterone + GnRH agonist. The Peto OR for the live birth rate was 2.44 (95% CI 1.62 to 3.67), for the clinical pregnancy rate was 1.36 (95% CI 1.11 to 1.66) and for the ongoing pregnancy rate was 1.31 (95% CI 1.03 to 1.67). The results for miscarriage and multiple pregnancy did not indicate a difference of effect.The last comparison (32 studies, 9839 women) investigated different progesterone regimens:intramuscular (IM) versus oral administration, IM versus vaginal or rectal administration, vaginal or rectal versus oral administration, low-dose vaginal versus high-dose vaginal progesterone administration, short protocol versus long protocol and micronized progesterone versus synthetic progesterone. The main results of this comparison did not indicate a difference of effect except in some subgroup analyses. For the outcome clinical pregnancy, subgroup analysis of micronized progesterone versus synthetic progesterone showed a significant benefit from synthetic progesterone (Peto OR 0.79, 95% CI 0.65 to 0.96). For the outcome multiple pregnancy, the subgroup analysis of IM progesterone versus oral progesterone suggested a significant benefit from oral progesterone (Peto OR 4.39, 95% CI 1.28 to 15.01).

AUTHORS' CONCLUSIONS

This review showed a significant effect in favour of progesterone for luteal phase support, favouring synthetic progesterone over micronized progesterone. Overall, the addition of other substances such as estrogen or hCG did not seem to improve outcomes. We also found no evidence favouring a specific route or duration of administration of progesterone. We found that hCG, or hCG plus progesterone, was associated with a higher risk of OHSS. The use of hCG should therefore be avoided. There were significant results showing a benefit from addition of GnRH agonist to progesterone for the outcomes of live birth, clinical pregnancy and ongoing pregnancy. For now, progesterone seems to be the best option as luteal phase support, with better pregnancy results when synthetic progesterone is used.