Can linea nigra predict your baby’s sex?

Once you find out you’re pregnant, waiting until around 20 weeks for your ultrasound to learn the sex of your baby can feel like a lifetime. Before options like the SneakPeek Early Gender Test were available, people turned to old wives’ tales, and myths to try and figure out their baby’s sex sooner.

Among these myths, the linea nigra one is a classic. According to the myth, if the line on your belly starts at your belly button and travels downward only, you might be expecting a baby girl. However, if the line extends up from your rib cage and down past your belly button, it’s believed you’re having a boy.

But does the shape or placement of the linea nigra actually predict the sex of your baby?

Not quite. Like similar myths passed down from generation to generation, this one doesn’t have any scientific evidence or medical research to back it up. It’s important for pregnant people to seek medical information from a reliable provider to ensure the best outcome.

Other Old Wives’ Tales About Baby Sex Prediction

The linea nigra theory isn’t the only old wives’ tale that claims to predict the sex of your baby before they’re born. There are plenty of fun (although non-scientific) methods parents have turned to over the years to predict their baby’s sex—and hey, they make for some pretty entertaining baby shower games.

Here are a few you might’ve heard:

• The ring gender test – Dangle a ring on a string over your belly. If it swings in circles, you’re supposedly having a boy. If it swings back and forth like a pendulum, you’re supposedly having a girl.
• Belly shape – It is believed that if your belly is high, it might mean you’re having a baby girl, and if you’re carrying low, it may mean you are having a baby boy.
• Cravings – If your sweet tooth is kicking in hard for ice cream, cookies, and other sweets, the cravings myth predicts a baby girl. But if you’re suddenly all about salty chips or pickles, the myth says it’s a boy.
• Complexion changes – There’s an old saying that baby girls steal your beauty. So, if your usual glow has been replaced by breakouts, you may be having a girl. If, on the other hand, your skin’s glowing and radiant, you may be having a boy.
• Baby’s heart rate and gender – One popular belief says that if your baby’s heart rate is over 140 beats per minute, you’re expecting a girl. If it’s under 140, this myth predicts a boy.

Learn more about pregnancy myths and explore 10 old wives’ tales for gender prediction.

Of course, these old wives’ tales are more for fun than fact. While they can be a lighthearted way to pass the time, they’re not backed by science, so take them with a grain of salt. For additional fun prediction methods, try our gender predictor quiz!

What is linea nigra?

We’ve answered the big question—does linea nigra predict baby gender? Now, let’s take a step back and explore what linea nigra is.

The name comes from Latin roots and means “black line.” While it’s not necessarily black for everyone, it usually appears darker than the surrounding skin on your belly.

Linea nigra typically shows up as:

• A vertical line measuring about ¼ to ½ inch wide
• A stretch of pigment running from the pubic bone to the belly button (and sometimes higher)
• A visible change that usually appears in the second trimester
• A line that darkens as pregnancy progresses

The exact hue of your linea nigra often depends on your skin’s natural pigmentation. For example, people with deeper skin tones may notice a darker, more prominent line due to higher levels of melanin, the pigment that gives skin, hair, and eyes their color.

What causes linea nigra?

While researchers are still studying the exact cause, it’s widely believed that hormonal changes from fetal development can cause changes such as linea nigra and other symptoms.

One key hormone thought to play a role is melanocyte-stimulating hormone, which is produced by the placenta during pregnancy. This hormone boosts the activity of melanocytes—the cells responsible for making melanin. It’s the same hormone that can cause your areolas to darken during pregnancy, and it may also contribute to other darkened areas of skin, like linea nigra.

Zooming out, linea nigra is part of a broader skin change known as hyperpigmentation, a condition in which certain patches of skin appear darker than the surrounding areas. During pregnancy, hyperpigmentation is common and completely normal, thanks again to fluctuating hormone levels and increased melanin production. In fact, 90% of women experience hyperpigmentation during pregnancy.

You might notice these changes in different areas of your body, from your belly to your face. Rest assured—they’re all part of your body’s natural response to pregnancy hormones.

Does linea nigra have a purpose?

So, we understand what may cause linea nigra, but what are some of its effects? In other words, is there a reason for linea nigra? Does it serve a purpose during pregnancy?

From a scientific perspective, not really. There’s no confirmed biological need for your body to produce a dark line down your belly.

That said, there are a few interesting theories:

• A visual guide for newborns – The areolas on your breasts naturally darken during pregnancy, possibly to help newborns spot the nipple and latch during those early days of feeding. Some experts think linea nigra could serve a similar purpose: acting like a landing strip that guides baby from belly to breast.
• A hormonal side effect – It’s also entirely possible that linea nigra is simply the result of all the hormonal shifts happening in your body. As your pregnancy hormones increase melanin production, the skin along your midline may darken, without serving any specific function—just another charming, hormonal souvenir.

Does everyone get linea nigra in pregnancy?

Not everyone wakes up one day to find a dark line stretching down their belly, but many pregnant people do notice some degree of skin darkening as their pregnancy progresses.

In fact, about 90% of pregnancies involve some form of hyperpigmentation, and one of the most common ways that shows up is through linea nigra. Whether or not you see it depends on a few key factors:

• Skin tone – People with medium to darker complexions tend to notice linea nigra more prominently due to naturally higher melanin levels.
• Hormonal fluctuations – Those with greater hormonal shifts, particularly elevated levels of melanocyte-stimulating hormone, may be more likely to develop the line.

Like most things during pregnancy, there’s no universal experience here. You might develop a barely-there line that only you can spot, or you may see a bold, dark line that deepens as the weeks go by. Or, you might not develop one at all.

All of these possibilities are completely normal. Linea nigra is just one of many ways your pregnant body adapts. Whether it shows up or not has no bearing on your health or the health of your baby.

Linea Nigra Timeline

Whether you’re eyeing your belly for clues about your baby’s sex or just wondering when the line might fade, here’s what to expect when it comes to the appearance (and disappearance) of linea nigra:

• When it shows up – Most people start noticing a faint line forming around the midpoint of the second trimester, typically around 20 weeks (though it can show up a bit earlier or later depending on your body).
• How it changes – What starts as a subtle shift in skin tone may deepen in color as your pregnancy progresses and hormone levels continue to rise. For some, the line extends only from the belly button downward; for others, it may start higher up, reaching toward the rib cage (one of the details that fuels the linea nigra and gender myth).
• When it fades – While many pregnancy-related hormones begin to drop soon after birth, linea nigra won’t vanish overnight. In most cases, it begins fading gradually over a few months postpartum, but the exact timing is different for everyone.

Get More Accurate Answers with the SneakPeek® Early Gender Test

While pregnancy myths like the linea nigra gender theory can be fun to explore, they aren’t exactly rooted in science. If you’re looking for answers you can count on, the SneakPeek Early Gender Test is here to help.

Available as soon as 6 weeks into pregnancy and with over 99% clinically proven accuracy, the SneakPeek Early Gender Test offers a reliable, science-backed way to learn your baby’s predicted sex, right from the comfort of your home. No myths and no guessing games. Just real answers—fast.

Join the 1 million+ parents who found out sooner with the SneakPeek Early Gender Test. Order yours today.