Mother's blood pressure before pregnancy may predict baby's gender: study

A pregnant woman is shown in this undated photo. (Pexels)

A woman’s blood pressure before pregnancy may be associated with her likelihood of delivering a boy or a girl, according to a new study led by a Canadian doctor.

Dr. Ravi Retnakaran’s research suggests that higher systolic blood pressure about 26 weeks before pregnancy increases a woman’s odds of delivering a boy, while lower blood pressure signals the birth of a girl.

Dr. Retnakaran, an endocrinologist at Toronto’s Mount Sinai Hospital, and his fellow researchers assessed more than 1,400 newly married women in Liuyang, China who were trying to conceive a child.

The women had their blood pressure checked roughly 26 weeks before conception. After adjusting for age, smoking, Body Mass Index, cholesterol, triglyceride and glucose levels, among other potential factors, the researchers concluded that the mean systolic blood pressure before pregnancy was higher in women who had a boy than those who delivered a girl.

Their findings were published in the American Journal of Hypertension.

“We asked the question: Are there factors in a woman’s physiology prior to pregnancy that might predict her likelihood of delivering a boy or a girl?” Dr. Retnakaran told CTV News Channel on Monday. “And we found that the only predictor of the sex of the baby was the maternal blood pressure.”

Dr. Retnakaran stressed that his study does not suggest that a woman can increase her odds of having a boy or a girl by manipulating her blood pressure.

“It’s not likely to be a causal effect – we don’t believe that for a second,” he said.

“Rather, we think that the blood pressure before pregnancy is giving an indicator of the mother’s underlying physiology and her likelihood of being able to carry a baby of a particular sex to term.”

Retnakaran explained that the sex of a fetus is determined by the father’s sperm, which provides either an X or a Y chromosome. But the viability of male and female fetuses after conception varies. Previous research has suggested that societal stressors, such as natural disasters, terrorism, wars or economic collapse, can affect a population’s sex ratio.

Retnakaran said his study suggests that maternal blood pressure may be a previously unrecognized biological factor when it comes to gender balance.

He said the potential link between blood pressure and fetal mortality needs to be studied further.

“If we better understand those processes, then we might be able to intervene…and reduce the number of babies that are lost during pregnancies,” he said.