From the linea nigra, carrying high or low and dangling a ring over your belly, the results aren’t always accurate.
Now, a new study, published in the American Journal of Hypertension, claims to have discovered a way to determine the sex of a baby.
It turns out, a mum to be's blood pressure 26-weeks before conception could influence the gender.
The study followed 1,411 newly-married Chinese women who were trying to fall pregnant. In total, 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," The Telegraph, London reports.
Speaking about the results, Dr Ravi Retnakaran endocrinologist at Mount Sinai Hospital in Toronto, who was also involved in the research, told The Independent: "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.
“This novel insight may hold implications for both reproductive planning and our understanding of the fundamental mechanisms underlying the sex ratio in humans."
This article originally appeared on Practical Parenting.