You are 3- 6% more likely to have a baby boy than a girl when using IVF to conceive. IVF increases the odds of a boy from 51 in 100 when conceived naturally to 56 in 100 with IVF. Up until recently, we have not known why. Recent research is shedding light on why exactly IVF produces more boys than girls, and suggest possible solutions.

Why are baby boys more likely to be conceived when using IVF?
Did you know you were more likely to have a baby boy when using IVF?

A team of researchers in China found that female IVF embryos had a lower survival rate and higher rate of growth defects. These defects resembled symptoms of impaired X chromosome inactivation.

Males have an X and Y chromosome, while females have two X chromosomes. The extra copy of the X chromosome in females is switched off during early embryo development by an epigenetic process known as “X chromosome inactivation”. The researchers found that X chromosome inactivation was impaired in female IVF embryos.

Research now continues on how to correct this gender skew in IVF. One possibility being explored is supplementing the IVF growth culture with the epigenetic modifier retinoic acid. Research so far is only on mouse models, and not available for humans at this time.

“To the best of our knowledge, retinoic acid is not used in IVF procedures for humans,” Tian said. “It should be noted that there are some differences in the mechanisms of X chromosome inactivation between mouse and humans, so whether the X chromosome inactivation status is impaired in human IVF embryos needs to be further determined. In addition, risk evaluation is required before the clinical application of retinoic acid in IVF.”

Separate research has shown that when the IVF cycle includes intra-cytoplasmic sperm injection (ICSI), a process where a single sperm is selected and inserted into the egg manually by the embryologist, more girls are born. Clearly there is a lot we still do not know about gender and IVF.

Other Creating a Family resources you will enjoy:

Did you know that you were more likely to have a baby boy with IVF?