The use of combined hormonal contraceptive for in-vitro fertilization cycle priming is not associated with decreased pregnancy rate in frozen embryo transfer cycles: a cohort study.

Background: The objectives of this study are to evaluate the cycle outcomes from IVF treatment preceded by oral contraceptive pills (OCP) priming compared to estradiol pretreatment and to determine if there is a role for OCP priming for those undergoing frozen embryo transfers.

Methods: The study took place at a university-affiliated fertility center in Canada. The study included in-vitro fertilization (IVF) antagonist cycles from Jan 2016 to Jun 2019. Those with protocol deviation or treatment cancellation were excluded.

Results: There were 2237 cycles by 1958 patients; 27% of cycles utilized OCP priming. The average age in the OCP group was 34 years old compared to 36.5 in the estradiol group (P<0.01). AMH was reported in 43% of patients and was 3.7ng/mL in the OCP group versus 2.2 ng/mL in the estradiol group (P<0.01). The number of oocytes (15.2 vs. 12.5) and number of blastocysts (4.6 vs. 3.3) were higher in the OCP group (P all <0.01). After adjusting for age and AMH with linear regression for the 978 cycles with recorded AMH (24% with OCP prime), a significantly higher number of oocytes (13.8 vs. 11.9, P=0.002) was still noted in the OCP group. There were 866 euploid embryo transfer cycles (28% with OCP prime). There were no significant differences in implantation (77% vs. 76%) or ongoing pregnancy rates (56% vs. 54%) between those who had a frozen embryo transfer after OCP primed compared to estradiol primed stimulation cycles (P all >0.6).

Conclusions: There were no differences in pregnancy outcomes from euploid frozen blastocyst transfers after OCP primed antagonist cycles compared to estradiol pretreatment. In fact, the use of OCP pretreatment was associated with increased oocyte yield, keeping in mind demographic differences with the OCP pretreatment group being younger with higher anti-Müllerian hormone and a higher prevalence of PCOS. Thus, OCP priming should still be considered in specific populations, such as those with oligo-ovulation or adequate ovarian reserve.