A Mother’s Blood Pressure Could Be Tied To The Baby’s Gender, According To A New Study

The factors that determine the sex of a baby have been the subject of scientific research (and lore) for millennia, but a recent study from Canada suggests that the mother’s blood pressure at 26 weeks prior to pregnancy could be a powerful indicator of the sex of the baby.

The study, which monitored 1,411 women who would go on to birth 739 boys and 672 girls found that, at 26 weeks, the mothers who would ultimately birth boys had a markedly higher average systolic blood pressure than those who would birth girls. The study corrected for many external factors of blood pressure including age, BMI, cholesterol, glucose, and triglycerides.

Now, this begs the age-old debate of causation vs. correlation, in that it’s possible that mothers at 26 weeks prior to pregnancy may have higher blood pressure due to other factors that are determinant in the sex of the child, but the team behind the study, led by Dr. Ravi Retnakaran at Mt. Sinai in Toronto, seems to feel that blood pressure itself may be the determinate.

As he puts it, the study "suggests that a woman's blood pressure before pregnancy is a previously unrecognized factor that is associated with her likelihood of delivering a boy or a girl. This novel insight may hold implications for both reproductive planning and our understanding of the fundamental mechanisms underlying the sex ratio in humans."

If this finding is supported, the question naturally follows: What are the ethical and practical implications of parents raising and lowering the mother’s blood pressure to influence the sex of the child?

It’s a chilling, somewhat unpleasant scenario, one that could become very real very quickly if this study’s findings are supported by more research and critical analysis.

There’s a lot of nonsense and pseudoscience that’s been aimed at predicting and influencing a child’s sex, but this TED video offers a pretty even-handed explanation of the factors at play without presupposing much:

Earlier studies have found that elements of stress in a culture or region can skew what Dr. Retnakaran calls the “sex ratio” among a population. The clear link between blood pressure and stress might go a long way to supporting those studies much as those studies could go a long way in supporting this finding.

The full study is available here in the American Journal of Hypertension.