A new study shows that preterm birth, pregnancy-induced high blood pressure and gestational diabetes are more common when a mom-to-be is carrying a boy.
Turns out, the gender of your baby can influence more than just the color you paint the nursery.
Researchers from the University of Adelaide studied births in Australia and found something surprising: That rates of birth complications seemed to be higher in instances when baby boys were born.
The research team, made up of members from the University of Adelaide's Robinson Research Institute, the University of Groningen in The Netherlands and the Pregnancy Outcome Unit of SA Health, looked at the link between the gender of a baby and adverse birth outcomes like preterm birth, pregnancy-induced high blood pressure and gestational diabetes.
The conclusions were not drawn haphazardly, either. In fact, the researchers studied Australian births extensively before finding this association. They looked at data of over 574,000 births over a 30-year period—this was the country's first population-based study to confirm gender's effect on birth outcomes.
"The major conclusion of our study is that the evidence is there and it is very clear: the sex of the baby has a direct association with pregnancy outcomes," the study's senior author, Claire Roberts, a professor at the University of Adelaide's Robinson Research Institute, said.
Here's a breakdown of how a baby's gender affects specific birth outcomes, according to the authors: Boys are 27 percent more likely to be born between 20-24 weeks gestation, 24 percent more likely to be born between 30-33 weeks gestation, and 17 percent more likely to be born pre-term between 34-36 weeks gestation. It's not just the babies who are at risk either: Mothers carrying boys are 4 percent more likely to develop gestational diabetes and 7.5 percent more likely to suffer from preeclampsia.
Think it's all bad news for women who are carrying sons? According to the researchers, mothers of girls actually have a 22 percent higher risk of developing early onset preeclampsia, which could require a pre-term delivery.
"Our results indicate there may be a need for specific interventions tailored to male and female babies, to prevent adverse outcomes for both child and mother. We're investigating other factors that may predict pregnancy complications, taking fetal sex into account," lead author Dr. Petra Verburg, PhD, from the University of Groningen, said.
"The placenta is critical for pregnancy success," Professor Roberts continued. "We believe that sex differences in placental function may explain the differences we're seeing in outcomes for newborn boys and girls, and their mothers. The next step is to understand the consequence of these differences and how they influence the path to pregnancy complications."