Maternal and child-health outcomes in different endometrial preparation methods for frozen-thawed embryo transfer: a retrospective study

Abstract

The purpose of this study was to analyse the obstetric outcome after frozen embryo transfer depending on the protocol used. The endometrial preparation during frozen embryo transfer (FET) was performed in the natural cycle (NC) with timing based on monitoring of the naturally occurring luteinizing hormone (LH) peak or in human chorionic gonadotropin (hCG)-triggered modified natural cycles (MNC), artificial cycle (AC) with hormone replacement therapy cycle and cycle with ovulation induction (OI). A retrospective cohort study was conducted between 2018 and 2020. Pregnancy, perinatal complications and neonatal outcomes were compared among patients treated during AC or MNC or OI protocols. After adjusting for the effect of gravidity, parity, pre-pregnancy body mass index (BMI) and number of miscarriages, the AC group had higher but not significantly different rates of gestational hypertension, preeclampsia and intrahepatic cholestasis of pregnancy (ICP) than women in OI and MNC groups. Significant differences were observed in the rates of placental adherence (15.30% in AC vs. 9.24% in MNC, p = 0.004) and postpartum haemorrhage (PPH) (24.33% in AC vs. 13.07% in OI, p = 0.003, 24.33% in AC vs. 16.24% in MNC, p = 0.002) among the three groups. In singletons, significant differences were observed in the rates of placental adherence (14.09% in AC vs. 8.57% in MNC, p = 0.002), AC and MNC groups had higher risk of PPH compared with OI group (18.36% in AC vs. 12.38% in MNC, p = 0.042 and 7.69% in OI vs. 18.36% in AC, p = 0.013). Neonatal outcomes were similar among the three groups except risk of small for date infants (0.35% in AC vs. 1.44% in MNC, p = 0.008). These findings are important in view of increasing use of frozen cycles and new policy of freeze-all cycles in in vitro fertilization (IVF). The results suggest a link between the absence of corpus luteum and adverse obstetric outcomes.

Keywords:

• Assisted reproductive technology
• frozen embryo transfer
• endometrial preparation
• pregnancy complications
• neonatal outcomes

Acknowledgments

The authors acknowledge the physicians, nurses and scientific staff of Department of Reproductive Medicine, Nanjing Maternity and Child Health Care Hospital.

Ethical approval

The study was approved by the local Ethics Committee of our hospital and was performed after obtaining informed consent from each patient.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by National Natural Science Foundation of China [81871210, 8197138, 81771536, 81471457] and Natural Science Foundation of Jiangsu Province [BK20171126].