OP01.04: Fetal growth after fresh and frozen embryo transfer and natural conception: a prospective cohort study
Year: 2024
Type: conference-abstract
Abstract: Fresh embryo transfer (ET) is associated with preterm birth, low birthweight, and small for gestational age (SGA), whereas frozen ET is associated with large for gestational age (LGA) and macrosomia. It is not known when in pregnancy these differences appear. In this prospective multicentre study, we explore fetal growth trajectories through gestation after fresh and frozen embryo transfer, in relation to natural conception (NC). Singleton pregnancies after fresh or frozen ET were included in gestational week 12, with four planned growth assessment ultrasounds between week 14 and 41. The Hadlock-3 formula was used to calculate estimated fetal weight (EFW). Generalised least squares models were used to evaluate the effect of fresh or frozen ET on fetal growth, while adjusting for relevant confounding factors. EFW as well as individual biometric measurements were analysed. Data on 683 NC pregnancies from a previously conducted study was included in the analyses as reference. The cohort consisted of 87 fresh ET, 175 frozen ET and 683 NC. In early pregnancy, there was no difference in fetal weight between the groups. Fresh ET showed a consistently lower growth rate than frozen ET and NC. At term, EFW was 5% higher in frozen and 4% higher in NC than in fresh ET. Similar differences were seen for fetal abdomen and head circumference. In early pregnancy, femur length was longer for both ET groups compared with NC, but later no differences were seen. The risk of being born SGA was higher for fresh ET than NC (aOR 2,8 (95% CI 1,2-6,9), whereas no differences could be seen between the other groups or when comparing the risks of LGA. Preliminary results from this prospective study, show a constantly lower growth rate in fresh ET pregnancies compared with frozen ET and NC but no differences in fetal growth between frozen ET and NC. Despite small differences in fetal weight between groups, the risk of being born SGA is increased after fresh ET.
DOI: 10.1002/uog.27877
Authors: M. Ageheim, L. Lindström, S. Iliadis, A. Skalkidou, E. Lampa, E. Elenis, E. Bergman
Institution: Uppsala University
Language: English
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W4402360774