Effect of Age on Decisions About the Numbers of Embryos to Transfer in Assisted Conception

Abstract

Summary Background Elective single-embryo transfer has been proposed as a strategy to reduce the risk of multiple birth and adverse pregnancy outcomes after in-vitro fertilisation (IVF). Whether this approach should be restricted to young women is unclear. Methods In a prospective study of UK Human Fertilisation and Embryology Authority data, we investigated whether perinatal livebirth outcomes varied by the number of embryos transferred in relation to maternal age. We compared rates of livebirth, multiple births, low birthweight ( Findings We assessed 124 148 IVF cycles overall, which yielded 33 514 livebirths. The odds ratios of livebirth were higher in women aged 40 years or older than in those younger than 40 years when two embryos were transferred compared with one embryo (3·12, 95% CI 2·56–3·77 vs 2·33, 2·20–2·46; p=0·0006 for interaction), but the absolute difference in risk of livebirth was smaller (0·090, 0·080–0·099 for women ≥40 years vs 0·156, 0·148–0·163 for those Interpretation Transfer of three or more embryos at any age should be avoided. The decision to transfer one or two embryos should be based on prognostic indicators, such as age. Funding None.