Glowing skin, cold hands and whether you are "carrying high or low" are all said the be indicators as to whether a pregnant women will give birth to a boy or a girl.
But now an intriguing new study, published in the American Journal of Hypertension, suggests that it is possible to determine the sex of of a baby months before it is even conceived.
Yup, it's true. Scientists in Canada
recently discovered that a woman’s blood pressure at around 26 weeks
before conception predicts if she will give birth to a boy or a girl.
And, according to the researchers, a higher systolic blood pressure signals she will deliver a boy, while a lower blood pressure suggests she could be about to conceive a baby girl.
Dr Ravi Retnakaran, endocrinologist at Mount Sinai Hospital in Toronto, explains: “It suggests that a woman's blood pressure before pregnancy is a previously unrecognised factor that is associated with her likelihood of delivering a boy or a girl.”
The team made the really interesting connection while trying to work out what determines the ratio between girls and boys in a population.
Previously, several studies have shown that stressful events such as wars, natural disasters and economic depression can change the proportion of boys and girls in a country. The difference, it seems, occurs because in stressful times one gender is more likely than the other to survive through pregnancy. Meaning, even though the conception sex ratio remains at 50:50, the birth ratio will alter depending on which sex is stronger.
For the study, 1,411 newly-married Chinese women were recruited all who were trying to become pregnant. Their blood pressure was checked at around 26 weeks before conception and they were followed through pregnancy. Overall the women gave birth to 739 boys and 672 girls.
After adjustment for age, education, smoking, Body Mass Index (BMI) , waist, cholesterol, triglycerides and glucose, mean systolic blood pressure before pregnancy was found to be higher in women who subsequently had a boy than in those who delivered a girl.
“When a woman becomes pregnant, the sex of a foetus is determined by whether the father’s sperm provides an X or Y chromosome and there is no evidence that this probability varies in humans,” added Dr Retnakaran
“What is believed to vary is the proportion of male or female fetuses that is lost during pregnancy. And this study suggests that either lower blood pressure is indicative of a mother’s physiology that is less conducive to survival of a male foetus or that higher blood pressure before pregnancy is less conducive to survival of a female foetus."
On the findings, Retnakaran speculates that this in the future will impact family planning.
“This novel insight may hold implications for both reproductive planning and our understanding of the fundamental mechanisms underlying the sex ratio in humans."
