There are a handful of random quirks that people swear can determine the sex of a pregnant person's baby. Some of them seem nonsensical, for example, if a pregnant person craves sweet foods over salty ones, then they're allegedly having a girl. Or if a pregnant person's hands are dry during their pregnancy, that supposedly means they're carrying a boy, or whatever.
But some of these so-called tells seem like they could be a bit more logical, because they actually involve the pregnant person's belly, like, if a person's bump is low, people say it means they're having a boy. (Despite lots of anecdotal reports, there's no scientific evidence that this is true, although the baby's size can determine the height of the belly.) And one intriguing old wives' tale that you may have heard suggests that the length of a pregnant person's "linea nigra," aka "pregnancy line," can indicate the baby's sex. So, is that just another urban legend, or is there some truth to it?
First, it's helpful to understand what the linea nigra is in the first place. The linea nigra is a dark line that runs from a person's navel to their pubic hair during pregnancy, according to the American College of Obstetrics and Gynecology. It's normal for people to experience all kinds of skin changes during pregnancy, due to fluctuating melanin-producing hormones. For example, it's common for some people's areola to get darker and larger during pregnancy to make it easier for the baby to see the nipples to breastfeed. It's also common for people to get something called hyper-pigmentation during pregnancy due to increased melanin deposits.
The linea nigra is just another normal pregnancy-related skin change, says Daniel Roshan, MD, FACOG, FAC, an Ob/Gyn in New York City. The length, width, and color of the linea nigra can vary depending on the person. For most people, the linea nigra shows up around the fifth month of pregnancy. Some people with darker skin may notice that their line is more pronounced, for others it's lighter and pale, and some people never notice a change at all. The point is, everyone is different.
As for the sex myth? Legend has it, if the linea nigra runs below your belly button, you're having a girl, and if it stops above your belly button, it's a boy. But unfortunately, "[the linea nigra] has nothing to do with fetal sex or delivery process," Dr. Roshan says. At the end of the day, unless you have sonographic vision, you can't tell anything about a baby's sex just by looking at the pregnant person's stomach. Not to mention, just because a baby is born assigned a sex doesn't mean anything about their gender identity.