Some parents can't wait to find out the sex of their baby, while others prefer to keep it a surprise. In the age of gender-neutral names and nurseries, finding out the sex of your baby may not be a priority for some mamas, but it turns out placentas aren't so gender-neutral.

According to a new study out of the University of Cambridge, the genetic profile of a baby's placentas is different depending on the baby's sex, and this might be one reason why expecting a girl puts moms at higher risk for pre-eclampsia and why being pregnant with a boy increases the risk of fetal growth restriction.

"In pregnancy and childbirth, the sex of the baby is at the forefront of many parents' minds, but we do not even think of the placenta as having a sex. This work shows that the placenta differs profoundly according to sex," says Professor Gordon Smith, who led the study.

Smith's team looked at placental and maternal blood samples from 4,000 firsttime mothers. They found that the placenta is different from other areas in the body in that genes that aren't different according to sex in other organs were within the placenta. One of these genes is responsible for placental levels of a metabolite called spermine.

Researchers also found moms who were expecting girls had higher levels of spermine in their blood and the placental cells from boys' placentas were more impacted by a drug that blocked spermine production.

The spermine that was found in higher levels in moms of girls was a predictor of complications. High levels indicated pre-eclampsia, and low levels were linked to poor growth.

The study basically backs up previous research that found moms of girls are more at risk for preeclampsia and baby boys are more at risk for restricted growth, and sheds some light on why that is.

"Better understanding of these differences could lead to new predictive tests and possibly even new approaches to reducing the risk of poor pregnancy outcome," says Smith.

Knowing the gender of your future baby may not help you decorate their room, but it could (one day) help your doctor keep mama and baby healthy.

You might also like: