Could Maternal Blood Pressure Be Predictive of the Baby's Sex?

An ultrasound done around 18-20 weeks of pregnancy can usually tell an expecting mother a key question she will having during her pregnancy: boy or girl? However, many people pursue predicting the sex of the baby into their own hands. Here are several old wive’s tales on how to tell if a woman is having a girl or a boy:

1. If you prefer sleeping on your left side, you are having a boy.
2. Extreme nausea means you are having a daughter.
3. If your hands are dry during pregnancy, you are having a boy; soft, expect a girl.
4. If you're craving citrus while pregnant, you're having a girl.
5. If altering hormones makes your skin break out, expect a girl.

There is no concrete scientific evidence proving any of these claims to be true, but a new study provides reason to believe that blood pressure before pregnancy could be predictive of a baby’s sex.

Beginning in 2009 and led by Dr. Ravi Retnakaran, scientists from Mount Sinai Hospital in Toronto and the Lunendfeld-Tanenbaum Research Institute developed a unique “pre-conception cohort” including young females with immediate plans to become pregnant.

Retnakaran and the team started out with over three thousand women, and around half were ultimately taken in for cardiometabolic characterization: a measurement of blood pressure, cholesterol, triglycerides, and glucose levels.

A group of women were not included in the final cohort for the potential of already being pregnant at the time, so the final study group ended up being 1411 women, with cardiometabolic characterization conducted at a median time of 26.3 weeks before pregnancy.

The model was designed to investigate the relationship between a woman’s health before and during pregnancy and the baby’s sex. Once the participants became pregnant, researchers followed up with them and continued to do so throughout the pregnancy to the day of delivery.

The 1411 pregnancies resulted in the birth of 739 boys and 672 girls. Researchers zeroed in on the impact of pre-pregnancy blood pressure, and they adjusted their for age, education, BMI, waist, LDL cholesterol, HDL cholesterol, triglycerides, and glucose to get a clear reading of the independent effect of blood pressure.

They found that the mean adjusted systolic blood pressure before pregnancy was found to be higher in women who ultimately gave birth to a boy than in those who had a girl.

Additionally, the prevalence of mothers delivering a boy increased as pre-pregnancy systolic blood pressure levels increased. Compared to the other measurements made during cardiometabolic characterization, the researchers concluded that pre-pregnancy systolic blood pressure was the “only significant predictor of having a male baby.”

“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,” Retnakaran said in summary of the study. “This novel insight may hold implications for both reproductive planning and our understanding of the fundamental mechanisms underlying the sex ratio in humans."

Retnakaran’s study was recently published in the American Journal of Hypertension.



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