Effect of embryo transfer number on singleton and twin implantation pregnancy outcomes after assisted reproductive technology
Barbara Luke1, Morton B Brown, Judy E Stern
1Department of Obstetrics and Gynecology and Reproductive Biology, Michigan State Univesity, East Lansing, Michigan 48824, USA. lukeb@msu.edu
Objective:
To evaluate the effect of embryo transfer number on singleton and twin pregnancy outcomes with one and two fetal heartbeats on early ultrasound, respectively.
Study Design:
The study included 23,645 singleton and 14,083 twin live births from the SART-CORS Online database of assisted reproductive technology cycles for 2004-2006. The data were limited to fresh embryo transfers among women who had additional embryos cryopreserved during the same cycle, resulting either in one fetal heartbeat on early ultrasound and a singleton live birth, or two fetal heartbeats and a twin live birth. Data were categorized by number of embryos transferred; the reference group was one for singletons and two for twins. The primary outcome measure was moderate growth restriction (birthweight for gestation z-score < -1), adjusted for potential confounders.
Results:
Risk for moderate growth restriction among singletons was increased by 15%, 23%, and 37%, respectively, with 2, 3, and > or = 4 embryos transferred, and among twins, by 50% and 105%, respectively, with 3 and > or = 4 embryos transferred.
Conclusion:
The data demonstrate a significant residual adverse effect on intrauterine growth from transfer of multiple embryos. Whether this effect is due to compromised embryo quality, degenerating implantation sites, or other etiology is unclear.
