Sex Ratio/Identical Twins in Blastocyst Transfer

WFWW-Sex Ratio and Identical Twinning in Blastocyst Transfer


One of the most frequent questions I am asked is whether IVF treatment, and blastocyst transfer in particular, increase the number of offspring of one sex.

According to a compilation of four studies published in the June 2009 issue of Fertility & Sterility, a higher male-female ratio after Day 5 blastocyst transfer compared with Day 3 cleavage-stage ET was 1.29:1 in favor of male offspring. This is not high enough to recommend this as a sex selection technique, but will be somewhat reassuring to those wanting a male child.

The study also looked at the chance of identical twins (monoztgotic twinning-MZT) in Day 5 transfers which has been said to be increased over Day 3 transfers or natural conception. They reviewed the results of nine studies incorporating almost 41,000 cycles and found the risk of MZT after blastocyst transfer was significantly higher compared with cleavage-stage transfer by a factor of 3.04:1. MZT is not a desirable result as it can create a more risky pregnancy for the babies, especially if they are in the same amniotic sac.