LAUSR

Frozen embryo transfer (FET) of euploid blastocysts in hormone replacement therapy (HRT) or natural cycle (NC): are there differences in obstetric, fetal and neonatal outcomes? Pregnancy complications, neonatal outcomes and fetal abnormalities are not increased after FET with PGT-A in singleton pregnancies. Since its introduction, PGT has been widely used in ART centers for preventing chromosomal and monogenic diseases. Despite its increased use, there are scarce and conflicting data about adverse pregnancy, fetal and neonatal outcomes. In one published study, the risk of preeclampsia and placenta previa was increased when PGT pregnancies were compared with non-PGT, while the incidence of gestational diabetes mellitus (GDM), preterm delivery, fetal defects and NICU (Neonatal Intensive Care Unit) admission were similar. According to other data, the rate of caesarean section in PGT pregnancies was high - around 80% in singletons. An observational, retrospective study was conducted between March 2015 and November 2019 in patients with singleton pregnancies after ART with PGT-A/FET/HRT and NC. A total number of 353 patients from two fertility centers (ART Fertility Clinics Dubai and Abu Dhabi, UAE), were included. They were divided into two groups according to the endometrial preparation for FET: group A: HRT (n = 225) and group B: NC (n = 128). Patients with primary / secondary infertility and at least one transferable euploid blastocyst after trophectoderm biopsy, achieving an ongoing singleton pregnancy after FET were included. Endometrial preparation for FET was either performed in a NC or an HRT cycle. For this study, the following pregnancy outcomes were recorded: GDM, preeclampsia and hypertension, obstetric cholestasis, placental abnormalities, mode of delivery, preterm delivery, gestational age at delivery, birth weight, fetal abnormalities and admission to NICU. There were no statistically significant differences in maternal and demographic characteristics of the studied groups. The mean maternal age was 34.05(20–45) and 34.26(23–47) years for group A and B respectively. The mean BMI was 28.31kg/m² (17.93–43.76) versus 27.93 (17.32–43.18). The ratio of nulliparous versus multiparous patients was 1:1 for both groups. Majority of the patients in both groups were of Arab ethnicity. The number of patients recorded as smokers was low and comparable in the groups. The mean gestational age at the time of delivery was comparable: 37.64 gestational weeks (24–41) versus 37.76 (26–41). The Caesarean section rate was around 50% for both groups. The rate of preterm delivery was comparable in both groups (16.9% and 18.8% for group A and B respectively). There was no detectable difference in the distribution of the birth weight in both groups with a median weight of 3000 grams of which 13.6% were low birth weight. In the studied groups, 30.5% had pregnancy complications with no observed statistically significant differences when the groups were compared. There was no increased incidence of fetal abnormalities. Admission to NICU was comparable and was related to prematurity. The limitations of the study are the retrospective design and the small number of participants. Wider implications of the findings: In patients with FET of an euploid embryo after PGT-A, the type of FET treatment preparation (HRT or NC) has no significant effect on pregnancy complications, birth weight and fetal abnormalities. The findings of the present study could be used to improve prenatal counselling for women undergoing ART with PGT-A. Not applicable