Multiple pregnancy is one of the most important and preventable complications of in vitro fertilization (IVF) and embryo transfer. The general clinical practice in many IVF clinics is to transfer four or five embryos to older women if available, since pregnancy rates are lower in women older than 35 years of age. However, it is not clear whether the risk for multiple pregnancy is also lower.
Our objective was to investigate whether transferring a higher number of embryos actually improves pregnancy outcome in older women, without increasing the risk for multiple pregnancy and to investigate other factors that may affect the occurrence of multiple pregnancy.
The setting was university-based IVF program at The Toronto Hospital.
The design was a retrospective case series.
The outcome of 1116 IVF cycles between January 1992 and December 1993 was investigated according to different age groups.
The main outcome measure was multiple pregnancies.
Seventy multiple pregnancies resulted from a total of 242 pregnancies. Overall pregnancy and multiple pregnancy rates were inversely correlated with age. However, when the data were adjusted for the number of embryos transferred, this trend disappeared. The result of multiple regression analysis showed that the multiple pregnancy rate was higher without improving the pregnancy rate when the number of embryos transferred exceeded three, regardless of the age of the patients, especially when more embryos were available than the number of transferred ones.
The number of embryos transferred should be limited to a maximum of three regardless of the age of patients, to reduce the high frequency of multiple gestations in an IVF program.
Cites: Am J Obstet Gynecol. 1966 Feb 15;94(4):490-65903669