Does blood pressure and sex of child have anything in common? Probably for mommies-to-be. Scientists, including an Indian-origin researcher, have revealed that woman's blood pressure before she gets pregnant could affect whether she has a boy or a girl.

The study was published in the journal of American Journal of Hypertension.

Researchers from Mount Sinai Hospital in Toronto found that those with lower blood pressure tended to have a girl, while higher blood pressure was an indication that a boy was more likely to be conceived. "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," said a researcher Dr Ravi Retnakaran. "This novel insight may hold implications for both reproductive planning and our understanding of the fundamental mechanisms underlying the sex ratio in humans," he said.

The team studied a group of women from Liuyang in China who were planning to get pregnant.

Their blood pressure was tested before and after conception and other factors, such as age, whether they smoked, weight and cholesterol, were also taken into account. The results indicated that 1,411 mothers had given birth to 739 boys and 672 girls. The findings indicate that those who had a female child had an average systolic blood pressure of 103.3mmHg before pregnancy, while for mothers of males the figure was 106, about 2.6% higher.

Fundamental biology means there is generally a 50/50 split in the sex ratio, although in humans there is a slight bias towards males. This is seen as nature's way of balancing out their slightly higher risk of premature death. But various methods of influencing the outcome have been suggested over the ages.

In 2009, a scientific study found that being closer to the equator meant a baby girl was more likely.