O-198 Obstetric and neonatal outcomes after natural frozen embryo transfer; results from a follow-up study of the Antarctica-2 RCT
Authors: Zaat T , De Bruin J P , Goddijn M , Van Wely M , Mol F 
Published: June 2023

Study question

Do obstetric and neonatal outcomes of women who conceived through home-based monitoring of the ovulation in natural cycle frozen embryo transfer (NC-FET) differ compared to hospital-controlled monitoring of the ovulation in NC-FET using a hCG trigger?

Summary answer

We found no differences in obstetric and neonatal outcomes when home-based monitoring versus hospital-controlled monitoring of the ovulation in women undergoing NC-FET.

What is known already

NC-FET is associated with lower risk of adverse obstetric and neonatal outcomes compared with artificial cycle FET. The question of how to prepare the endometrium for FET, has now gained even more importance and taken on the dimension of safety into account as it should not simply be reduced to the basic question of effectiveness.

Study design, size, duration

Between April 10, 2018 and April 13, 2022, 1464 women were included in the Antarctica-2 RCT (n = 732 home-based monitoring and n = 732 hospital-controlled monitoring). For this study we performed a follow-up study in order to investigate obstetric and neonatal outcomes of the participating women with live births after the Antarctica-2 trial.

Participants/materials, setting, methods

We included only singleton livebirths. Main outcomes were gestational age, preterm birth (PTB), very preterm birth (very PTB), birth weight, large for gestational age (LGA) and small for gestational age (SGA). Additional outcomes included: gestational diabetes (GDM), hypertensive-disorders-of-pregnancy (HDP), pre-eclampsia (PE), abnormal placentation (including placenta previa and accrete), hospital admission during pregnancy, congenital anomalies and neonatal death. We calculated risk ratios and absolute risk differences (95% CI) using per protocol analysis.

Main results and the role of chance

Both studyarms resulted in similar live birth rates. Singleton live birth occured in 146 of 732 women (19.9%) following home-based and in 148 of 732 women (20.2%) following hospital-controlled monitoring. The mean gestational age in weeks was 39.0 (SD 0.3) for the home-based monitoring group versus 39.3 (SD 0.2) for the hospital-controlled monitoring group. We found no significant differences in preterm birth (5/146 versus 11/148, RR 1.00, 95% CI 0.90 – 1.10) or very preterm birth (1/146 versus 2/148, RR 1.00, 95% CI 0.90 – 1.10) for home-based versus hospital-based monitoring. Very preterm birth only occurred once in the home-based monitoring group. The mean birth weight was 3504.0 (SD 47.7) for the home-based monitoring group versus 3532.1 (SD 48.1) for the hospital-controlled monitoring group. We found no significant differences in LGA (20/146 versus 18/148, RR 1.00, 95% CI 0.90 – 1.10) and SGA (12/146 versus 12/148, RR 1.00, 95% CI 0.90 – 1.10) for home-based versus hospital-based monitoring. Also, no differences were found in HDP, PE, abnormal placentation, GDM, hospital admission during pregnancy and congenital anomaly. One neonatal death due to pulmonary hypoplasia occurred in the home-based monitoring group after very PTB.

Limitations, reasons for caution

The outcomes of HDP, PE, abnormal placentation, GDM and hospital admission during pregnancy were patient-reported and confirmed by hospital-files after contacting the participating centers.

Wider implications of the findings

NC-FET is the preferred treatment in women with ovulatory cycles undergoing FET. When home-based monitoring is compared to hospital-controlled monitoring in NC-FET we found no difference in obstetric or neonatal outcomes.

Trial registration number

not applicable