Original research••

Use of oestradiol in luteal phase to improve scheduling of ovarian stimulation in infertile patients treated with in vitro fertilisation

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Abstract

Background The organisation of oocyte retrival presents significant challenges for both clinicians and patients. Methods such as the use of oral contraceptives prior to stimulation adversely affect outcomes. Our objective was to determine if a longer pretreatment with oestradiol for flexible oocyte retrieval scheduling affects the results of ovarian stimulation in patients requiring in vitro fertilisation (IVF).

Methods This retrospective, descriptive, cohort study included 194 women recruited from an academic affiliated private infertility clinic in Mexico. Patients requiring IVF treatment were pretreated with oestradiol before undergoing ovarian stimulation as standard care in our centre. The short group (group A, n=98) included patients in whom oral oestradiol was withdrawn 2 or 3 days after initiating menstruation, while the extended group (group B, n=96) included patients who used oestradiol until 4–8 days after starting menstruation.

Results The clinical pregnancy rate was comparable between groups B and A, at 65.6% and 57.1%, respectively, with relative risk (RR) 1.15 (95% CI 0.92 to 1.44, p=0.2412). The implantation rate was not significantly higher in group B than in group A (40.1% vs 34.2%), with an RR of 1.17 (95% CI 0.81 to 1.70, p=0.4566). The numbers of oocytes retrieved, metaphase II oocytes, fertilised oocytes and embryos transferred, and the miscarriage and live birth rates did not significantly differ between the two groups.

Conclusions Administration of oestradiol in a long regimen during luteal phase does not have a deleterious effect on ovarian stimulation. Moreover, it provides a scheduling alternative that is convenient for both patients and the medical team.

What is already known on this topic

The scheduling of oocyte retrival can be challenging in in vitro fertilisation cycles using gonadotropin-releasing hormone (GnRH) antagonists. The use of pretreatment with oestradiol presents an option for optimising the timing of oocyte retrieval.

What this study adds

This study assessed the effects of initiating oestradiol treatment during the luteal phase compared with an extended oestradiol regimen (4–8 days postmenstruation) for optimising the timing of oocyte retrieval and embryological procedures. The findings indicated that extending the pretreatment period with oestradiol did not result in any detrimental effects.

How this study might affect research, practice or policy

This study shows that oestradiol in the luteal phase can flexibly schedule oocyte capture in GnRH antagonist cycles, improving infertility care and resource use at clinics.

Introduction

Controlled ovarian stimulation requires coordinated follicular growth in response to gonadotrophins. Disparities in follicular size can decrease the numbers of mature oocytes and embryos, and the chances of conception. The main protocols for ovarian stimulation use gonadotropin-releasing hormone (GnRH) antagonists and agonists. Although these two protocols have comparable results,1 there is still a perception that cycles with antagonists are less flexible, especially when in vitro fertilisation (IVF) cycles must be scheduled on specific days or weekends. A GnRH agonist protocol predicts the day of oocyte retrieval; however, the starting day of gonadotropins cannot be changed with a GnRH antagonist protocol, which is more patient-friendly and therefore leads to better adherence to treatment.2

The use of combined oral contraceptives prior to controlled ovarian stimulation or delaying the day of the human chorionic gonadotropin (hCG) trigger in GnRH antagonist cycles has been reported.3 4 These strategies lead to higher gonadotropin use, longer stimulation periods and lower ongoing pregnancy rates. The negative impact may be due to progestin in contraceptives affecting the stimulated endometrium, resulting in the decreased use of combined oral hormones with antagonists for cycle scheduling.5 6

Some schemes have extended the use of exogenous estrogens beyond the first day of menstruation, from preluteal phase to day 1–7 of the cycle, to schedule oocyte retrieval and embryo transfer on weekdays. Initially, Fanchin et al described oestrogen administration in the luteal phase and found a significant reduction in basal follicular size and improved timing of follicular growth.7 8 Other authors reported an increase of ongoing pregnancy rates and a higher birth rate directly proportional to a greater number of days of oestradiol exposure to suppress follicle-stimulating hormone (FSH).9

The goal of oestradiol priming is to maintain a homogeneous follicular cohort during ovarian stimulation due to negative feedback on the pituitary for FSH secretion in the luteal-follicular transition.7 We adopted this alternative in our clinic in the regular care of patients requiring IVF. However, few studies have evaluated the results of prolonging the use of oestrogens and postponing the start of ovarian stimulation in different types of patients for flexible cycle scheduling. In this study, we evaluated the effects of shorter and longer oestradiol administration during the luteal phase until the day of FSH administration for optimal cycle scheduling.

Materials and methods

Study design

This retrospective, descriptive, cohort study included 194 women recruited from an academic-affiliated private infertility clinic in Mexico. Patients undergoing IVF treatment at our centre are routinely pretreated with oestradiol prior to ovarian stimulation as part of standard care.

Study population

Consecutive patients (20–40 years old) with primary infertility undergoing their first cycle of IVF for diverse causes of infertility were recruited from a private academic centre (Instituto de Ciencias en Reproduccion Humana) from January to December 2019. Patients were excluded if they were diagnosed with severe endometriosis or severe male factor (defined as oligozoospermia <5 million/mL in sperm analysis performed according to the WHO Manual fifth edition).

The short group included patients in whom oral oestradiol was withdrawn 2 or 3 days after initiating menstruation (group A, n=98) (as is regularly performed for stimulation start without oestradiol priming) and the extended group (group B, n=96) included patients who used oestradiol until 4–8 days after starting menstruation.

Oestradiol preparation

All patients received oral oestradiol pretreatment in the luteal-follicular transition of the cycle prior to ovarian stimulation with oestradiol valerate (Primogyn, Bayer Mexico) at a dosage of 4 mg daily starting 7 days after ovulation in the menstrual cycle prior to ovarian stimulation until the day of gonadotropin administration. In group A, oestradiol was suspended on day 2 or 3 after menses started with controlled ovarian stimulation. In group B, oestradiol was suspended on day 4–8 of the cycle, and controlled ovarian stimulation was subsequently initiated.

Stimulation protocol, follicular aspiration and oocyte retrieval

Ovarian stimulation was performed with 150–300 IU per day of recombinant FSH/recombinant luteinising hormone or recombinant FSH alone, individualised according to the criteria of the treating physician, starting on the day on which stimulation was desired, between days 2 and 8 of the menstrual cycle. A flexible protocol was implemented using 0.25 mg GnRH antagonist (Cetrotide, Serono Mexico) when the largest follicle size reached 14 mm. hCG (Choriomon, Ferring Mexico) was administered at a dose of 10 000 IU to trigger final maturation when at least two follicles reached 18 mm, as previously described.10 Follicular aspiration was performed 36 hours after hCG trigger, under general intravenous anaesthesia. Ultrasound-guided vaginal puncture was performed with a 17 G needle and a vacuum pump system (100 mm Hg) while maintaining the collecting tubes at 37°C.

Oocyte-cumulus complexes were identified and maintained in Global for Fertilisation medium (LifeGlobal) containing 5% human serum albumin and preserved in an environment containing 6% CO₂, 5% O₂ and 89 % N₂ at 37 °C for at least 2 hours. Then, oocytes were decumulated with 80 IU/mL hyaluronidase and the nuclear maturity status was assessed.

Intracytoplasmic sperm injection and embryo culture

Intracytoplasmic sperm injection of metaphase II oocytes was performed according to previously described techniques.11 Global Total Medium (LifeGlobal) was used for embryo culture. Fertilisation was confirmed by the presence of two pronuclei and two polar bodies at 16–18 hours after microinjection. Embryos were transferred to fresh medium on day 3 when the culture was extended to the blastocyst stage (day 5).

Embryos at the cleavage stage were classified as excellent when they displayed less than 10% fragmentation and four symmetrical blastomeres on day 2 and less than 10% fragmentation and eight symmetrical blastomeres on day 3, without multinucleation, according to Veek’s criteria.12 Blastocyst morphology was classified based on the criteria of Gardner and Schoolcraft.13

Embryo transfer and luteal phase support

Good quality embryos were transferred on day 3 or 5. The clinician decided the number of embryos to transfer based on the patient’s age, history of previous cycles and embryo quality. Embryo transfer was performed under ultrasonographic guidance with a Frydman Ultrasoft catheter (Laboratoire CCD). Patients rested for 40 min to 1 hour after embryo transfer.

Patients received 4 mg per day oral oestradiol valerate (Primogyn, Bayer Mexico) and supplementation with 50 mg per day intramuscular progesterone (Actavis, USA) as luteal phase support. These were initiated 24 hours after oocyte recovery and continued until 12 weeks of gestation when pregnancy was achieved. β-hCG was quantified 14 days after embryo transfer. The presence of an intrauterine gestational sac from 5 weeks of gestation was defined as clinical pregnancy. The implantation rate was defined as the number of intrauterine gestational sacs divided by the number of embryos transferred. Early abortion or early gestational loss was defined as clinical pregnancy loss without fetal heart activity or with disappearance of the fetal heart rate before 12 weeks of gestation.

Statistical analysis

No specific calculation of sample size was performed, and consecutive patients were included in the analysis.

Continuous data are presented as the mean with SD. The t-test was used for hypothesis testing of continuous variables. Proportions were evaluated with Fisher’s exact test, and the relative risk (RR) and 95% CIs were calculated. P values <0.05 were considered statistically significant.

Results

There was no statistically significant difference between groups A and B in terms of age and the reason to perform the IVF cycle, and tubal factor was the most frequent cause of infertility in both groups (table 1). A statistically significant difference was found only in height (table 1).

Table 1

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Demographic characteristics of patients in the two groups

Comparison of the number of days of stimulation, endometrial thickness, and the total dose of gonadotropins between the two groups did not show statistically significant differences. In relation to ovarian stimulation, the oestradiol level on the day of trigger was statistically significantly higher in group B than in group A (2187.5 vs 1707 pg/mL, p=0.0434). There was no statistically significant difference in the serum progesterone levels on the day of trigger between the two groups. (0.6 vs 0.6 ng/mL, p=1.000) (table 2). Although we increased the number of days elapsed before starting gonadotropins in group B, neither the number of days of stimulation (9.4±1.4 vs 9.6±1.3, p=0.3040), nor the total dose of gonadotropins used (2745.7±870.6 vs 2829.2±881.8 IU, p=0.5077) increased.

Table 2

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Comparison of cycle characteristics between the two groups

There were no cycle cancellations in either group. In relation to the results of IVF cycles, there were no statistically significant differences in the numbers of oocytes retrieved, metaphase II oocytes, fertilised oocytes and embryos transferred (table 3). The clinical pregnancy rate was not statistically significantly higher (p=0.2412) in group B (65.6%) than in group A (57.1%) with an RR of 1.15 (CI 0.92 to 1.44). The implantation rate was not statistically signicant (p=0.4566) higher in group B than in group A (40.1% vs 34.2%), with an RR of 1.17 (CI 0.81 to 1.70). The live birth rate per transfer (47.9% vs 52.08%) did not significantly differ between the two groups (p=1.0000) with an RR of 1.08 (CI 0.82 to 1.44) (table 3).

Table 3

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Comparison of reproductive outcomes between the two groups

Discussion

Our results demonstrated that the number of days of stimulation and total gonadotropin dose were similar in the two groups, with no cancellations. The cancellation rate in the study by Guivarc’h-Levêque et al9 was 11.47%. Similarly, Blockeel et al14 could not perform oocyte retrieval for different reasons in 11.6% of the assigned patients. Reproductive outcomes were not affected by delayed stimulation or prolonged oestradiol exposure, and neither of these two studies found a difference in the numbers of oocytes retrieved, transferred and cryopreserved, the pregnancy rate and the live birth rate. The primary limitations of our study are that the small sample size was small and all patients were treated at a single centre. Nonetheless, our findings warrant further research with a larger sample size to thoroughly investigate the extent to which oestradiol valerate treatment can delay the initiation of stimulation and its impact on clinical outcomes.

Two studies analysed the use of oestradiol pretreatment extending beyond the first or second day of the stimulation cycle. One study9 found no statistically significant differences in the numbers of oocytes retrieved and embryos obtained and reported that women exposed longer to exogenous oestradiol for longer tended to have higher pregnancy rates. The other study14 investigated the use of oestradiol from day 25 prior to estimated menses during 6–10 days for scheduled oocyte retrieval from Monday to Friday compared with a control group that received conventional antagonist stimulation and reported that the clinical pregnancy rates per cycle initiated were similar in the pretreatment group. The finding that pretreatment with oestradiol valerate has no detrimental effect means that a significantly lower proportion of patients need to undergo oocyte retrieval during a weekend day and such pretreatment can be a valuable tool for the organisation of an assisted reproduction centre.

Another pretreatment scheme with oestradiol in the follicular phase was proposed by Aslan et al,15 where 6 mg of oestradiol valerate was administered to patients during the beginning of the luteal phase until day 4–7 days of the stimulation cycle (average of day 5), for flexible scheduling of IVF cycles. These patients were compared with a group treated with a GnRH antagonist that did not receive any medication prior to ovarian stimulation. No differences were observed in pregnancy rates and implantation, and oocyte recovery on the day desired by the clinician was unaffected. In this study, the use of oestradiol in luteal phase and follicular phase for oocyte retrieval on a specific day preferred by the clinician did not significantly affect the number of oocytes recovered and reproductive results.

Chang et al16 suggested continuing oestradiol administration for an even longer period during ovarian stimulation without compromising reproductive outcomes. Their approach involved extending oestrogen usage into the luteal phase by administering it from day 21 of the preceding cycle until the day of hCG administration. The aim of this modification was to prevent a rebound effect on endogenous gonadotropins, and the hypothesis was that the extended use of oestrogens through ovarian stimulation would increase the stimulatory effect of FSH on granulosa cell receptors and improve embryo quality, obtaining even better results compared with the withdrawal of oestradiol on day 2–3. This aligns with our results.

A retrospective study17 of cycles with a GnRH antagonist in low and normo-responders evaluated the benefits of oestradiol pretreatment vs a control group. No statistically significant differences were found in the number of oocytes recovered; however, in both normal and low responders, the oocyte maturity rate and number of frozen embryos were significantly higher in the pretreatment group. No impact was reported on the cancellation rate and clinical results.17 This may support the hypothesis of Fanchin et al7 that follicular synchronisation increases oocyte maturity.

Our finding that oestradiol levels on the hCG trigger day were significantly increased in group B is probably explained by the greater number of days of oestradiol exposure. We did not observe statistically significant differences in reproductive outcomes, with longer oestradiol exposure.

Conclusions

A long course of oestradiol pretreatment starting during luteal phase for oocyte capture scheduling does not have a deleterious effect on the response to ovarian stimulation and provides similar pregnancy and implantation rates. Furthermore, the use of oestradiol pretreatment may provide an advantage for scheduling cycles that improves the quality of care of infertile patients.