GnRHa for trigger and luteal phase support in natural cycle frozen embryo transfer – A proof of concept study

We aimed to explore whether ovulation induced by a GnRH analogue (GnRHa), followed by daily GnRHa luteal support provides an efficient platform for natural cycle frozen embryo transfer (NC-FET). In this cohort study, included were normo-ovulatory women who underwent NC-FET cycles, under the age of 40, with an antral follicle count > eight. Ovulation was triggered with triptorelin (0.2 mg Decapeptyl; Ferring), and luteal support was initiated two days later, using a Nafarelin inhaler (Synarel, Pfizer), 200 μg twice daily. Main outcome measures were luteal estradiol and progesterone levels (three to five days following ovulation), implantation rate, ongoing pregnancy rate, early pregnancy loss rate, and live birth rate. Fifty-one patients treated between 2017 and 2018 were included. Mid luteal progesterone levels among study patients, were non-significantly different between patients who achieved pregnancy and those who did not, but differed significantly on day 14 following ovulation (86.0 ± 31.3 vs. 9.8 ± 9.5 nmol/L, respectively, p < 0.001). Twenty-three patients achieved a clinical pregnancy (45.1 %); interestingly, there were no chemical pregnancies. Three pregnancies ended in an early abortion at 6-7 weeks gestation, and 20 pregnancies continued as ongoing pregnancies (39.2 %). One patient had a late abortion at 16 weeks gestation, and 14 had a live birth. In conclusion, in this proof of concept study, inducing ovulation with a bolus of GnRHa in NC-FET, followed by repeated daily GnRHa administration, resulted in satisfactory luteal phase steroid levels and high ongoing pregnancy and live birth rates.