When it comes to determining the sex of your unborn baby, there are old wives’ tales galore. However, a study published in January 2017 in the American Journal of Hypertension may have some real science on the matter. Want to know whether it’s a boy or a girl without undergoing expensive and invasive procedures? Check your blood pressure.

According to a new study, mom’s blood pressure may be an accurate predictor of her unborn baby’s sex. The study, led by Dr. Ravi Retnakaran, endocrinologist at Mount Sinai Hospital in Toronto, and an investigator with the Lunendfeld-Tanenbaum Research Institute, came to the conclusion that “Maternal blood pressure before pregnancy is a previously unrecognized factor that may be associated with the likelihood of delivering a boy or girl.” Pregnant participants who had higher blood pressure were more likely to have boys. That was true regardless of other factors like smoking and BMI.

There are only a few other evidence-based tests on the table for knowing the sex of your baby before it’s born. An ultrasound can generally predict whether the baby is a boy or a girl with 90 percent accuracy, though parents generally have to wait until the fetus is at least 18 weeks along. There’s also a fairly new blood test pregnant women can take that’s even more accurate—by analyzing the mom’s blood for fetal DNA, it can correctly identify the baby’s sex up to 98.6 percent of the time, and as early as 7 weeks into the pregnancy. There are also more invasive tests such as amniocentesis and chorionic villus sampling, but those are usually reserved for pregnancies with a high risk of genetic or chromosomal disorders.

The list of myths, on the other hand, goes on and on. Here are just a few that WebMD mentions: all-day morning sickness means you’re having a girl; craving sweets means you’re having a boy, and craving sour foods means you’re having a girl; carrying low means you’re having a boy, carrying high means you’re having a girl; None of these are backed by science, but now we know one method that is: just check your blood pressure.