CHENNAI: In an interesting study, a team of researchers in Canada and China, led by a doctor of Indian origin, has found that maternal blood pressure may be linked to the likelihood of a woman delivering a boy or girl child.
The study, ‘Maternal Blood Pressure Before Pregnancy and Sex of the Baby: A Prospective Preconception Cohort Study’, has found that the women who delivered male child had higher blood pressure during the weeks ahead of conception than those who had female children.
“This study shows an association between a woman’s blood pressure before pregnancy and her likelihood of delivering a boy or girl when she becomes pregnant,” Dr Ravi Retnakaran of Mount Sinai Hospital, Toronto, told The New Indian Express.
“As such, this study is providing novel insight that a woman’s blood pressure may be a previously unrecognised indicator of maternal factors that contribute to the sex ratio (the proportion of boys to girls at birth),” he added.
The team of seven researchers working in Canada and China pursued the population-level sociologic studies that suggested that adverse societal conditions may affect foetal viability in a sex-specific manner and thus modify sex ratio. That is, there could be certain physiologic features that are related to the likelihood of a woman delivering a boy or girl.
For this, 1,411 newly-married women in Liuyang, China, were chosen. Their cardiometabolic characterisation including blood pressure, cholesterol, triglycerides, and glucose were monitored approximately 26 weeks ahead of conception. They were observed during pregnancy till delivery – 739 had boys, while the rest 672 delivered daughters.
Results showed that the “systolic blood pressure before pregnancy was higher in women who delivered a boy than in those who had a girl,” said the study that was published in the latest issue of American Journal of Hypertension. The pre-pregnancy difference in blood pressure between mothers of boys and girls was not present during any trimester of pregnancy, the study added.
The result is as interesting as it is intuitive.
There have been a series of studies on how sex ratio is impacted by stressful events – trouble in Northern Ireland, the Rodney King Riots, Breivik and Sandy Hook shootings, students and worker riots in France in 1968, the 1995 sarin nerve gas attack on the Tokyo subway by the Aum Shinrikyo religious cult, the September 11 attacks of the World Trade Centre, the assassination of President John F Kennedy, and even the impact of economic stress on sex ratio in East and West Germany.
However, Dr Retnakaran hastened to add that the results definitely does not demonstrate causality. “Rather, the blood pressure before pregnancy may be a marker of underlying physiology that relates to the likelihood of sex-specific foetal survival and hence the likelihood of delivery of a boy or girl.”
What does this study mean in a country like India where the desperate demand for male children has led to female foeticide and infanticide?
“It does not show that raising or lowering blood pressure will change the likelihood of having a boy or girl. The manipulation of blood pressure to affect the likelihood of having a boy or girl would be an inappropriate extrapolation from these data that we would strongly caution against. Rather, this study opens new avenues for investigation into the determinants of foetal survival and hence the sex ratio at birth in humans,” he added.