Some Canadian scientists have said that it is possible to determine the sex of a baby months before it is even conceived.
They say that a woman’s blood pressure at around 26 weeks before conception could tell if she will have a boy or a girl.
Higher systolic blood pressure signals she will deliver a boy while lower suggests a girl,” says endocrinologist at Mount Sinai Hospital in Toronto, Dr. Ravi Retnakaran.
In a study published in the American Journal of Hypertension, the researchers reached the conclusion as they tried to determine what is responsible for the ratio between girls and boys in a population.
In the new study, the mean systolic blood pressure reading for women who had boys was 106 mm Hg, compared to 103 mm Hg for those who had girls, in the months leading up to conception.
“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 foetuses that is lost during pregnancy.
“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.
“This novel insight may hold implications for both reproductive planning and our understanding of the fundamental mechanisms underlying the sex ratio in humans,” he disclosed.
For the study, 1,411 newly-married Chinese women were recruited, all of whom 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, 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.
Fertility expert Prof Charles Kingsland, of Liverpool Women’s Hospital, said: “We have been aware that more male fetuses miscarry than females and more females are born for obvious biological reasons, namely you need more women in the world to have children.
“There is also some evidence that you are more likely to miscarry a boy when you are compromised either by health or environmental issues. So, I suppose, blood pressure changes in these circumstances might affect conception of different sexes.
“This study is therefore very interesting. However, it does not take into account the potential physiological aspects of race.
“Will those changes be the same in the Caucasian or Afro Caribbean populations in the world. And what if you want a girl? Do you just go and live in Syria for a few months?”
However, some experts were skeptical about the results.
A consultant in Reproductive Medicine and Surgery at the Hammersmith Hospital in West London, Geoffrey Trew, said:
“I haven’t heard anything like this before. I would be very surprised that a BP measurement, which is notoriously variable, could dictate sex 26 weeks before. Some reptiles can have sex differences due to temperature changes at the time of early foetal growth, but not 26 weeks beforehand.”