Signs of Having a Girl (and a Boy): 14 Signs, Checked

Most “girl” signs share a theme: a harder, more uncomfortable pregnancy. More sickness, worse skin, bigger mood swings, a sweet tooth. The idea is old and turns up in many cultures, often phrased as a daughter “taking” something from her mother.

Morning sickness is the one in this group with real data behind it, and the data does not back the saying. In a study at Johns Hopkins, Perry, DiPietro and Costigan asked 104 pregnant women who did not yet know the baby's sex what they expected and why, then checked against the birth. How much nausea and vomiting a woman had was not related to whether she had a boy or a girl. The same study found no link for bump shape either, so two of the three classic “girl” signs fail on the same evidence.

Skin, hair, mood and cravings are a different story: nobody seems to have tested them. We searched PubMed for each one alongside fetal sex and found studies on hormones, stress and child development, but none asking whether these changes predict a girl. That leaves the confident claims you read online resting on memory and anecdote.

Our longer look at the old wives tales gender predictions walks through the full Johns Hopkins study, including the surprise result about which mothers guessed best.

The “boy” list is mostly the girl list in reverse: an easy first trimester, a neat bump carried low and out front, salty cravings, glowing skin, thick hair. A few are their own thing, like a linea nigra running above the belly button or permanently cold feet. Here is how they fare.

• Carrying low: tested in the Johns Hopkins study, and bump shape was not related to sex. A bump is also judged by eye, so the same shape can be called “high” by one relative and “low” by another.
• A slower heartbeat: tested on 477 early scans. Boys averaged 154.9 beats a minute and girls 151.7, both above the famous 140 line, and the gap was not significant.
• Linea nigra, cold feet, a partner who gains weight: our PubMed searches found no study testing any of them.
• Breast growth: the one “boy” sign with a measured result, which deserves its own section below.

Breast growth and boys

Researchers at the University of Wrocław in Poland scanned the breasts of 93 pregnant women in 3D in each trimester (Żelaźniewicz & Pawłowski, 2015). Mothers of boys had somewhat larger breasts at each stage, but that difference was not significant. The increase in size across pregnancy was larger on average in mothers carrying boys, and that difference was significant (P = 0.039). Asymmetry, the “one side bigger” version of the tale, was not related to the baby's sex.

This is one small study, it used laboratory 3D scanning rather than a tape measure, and the result is a difference between averages. There is no cut-off a mother could apply at home, and we have not found it repeated in a larger group. It is interesting biology, not a prediction method.

You will meet many more signs than these fourteen. Four questions sort them quickly.

1. Is there a study, and is it linked? A real finding has a journal, a year and a number of pregnancies. “Studies show” with no link usually means nobody looked.
2. Was the prediction written down before the birth? Signs remembered afterwards are bent by what the baby turned out to be. The Johns Hopkins team asked women in advance for exactly this reason.
3. Is it a group average or a rule? Even the one sign with a link describes an average across many mothers. A rule that works for one pregnancy would need a far stronger effect than that study found.
4. Could it be a health issue in disguise? Some symptoms that show up on online lists, like pain or heavy sickness, belong with your midwife, not on a scorecard. We leave those off on purpose.

A sign that picks one of two answers will match about half of all babies with no help at all. Then memory does the rest. A friend whose sickness “predicted” her daughter tells the story at every baby shower; a friend whose sickness came with a son rarely brings it up. Over years, the hits become folklore and the misses disappear.

Families with several children add another twist. Research on 146,064 US pregnancies suggests some families lean towards one sex more than a plain coin flip would, which can make a sign look reliable inside one family for reasons that have nothing to do with the sign. Our page on second baby gender prediction explains that study.

None of that makes the signs a waste of time. Guessing is half the fun of the months before you know, and a sign can be enjoyed the way a horoscope is enjoyed. The Chinese gender calendar is our own favourite folk method, and it was tested on 2,840,755 births and came out at chance too. We enjoy it anyway; we just keep score honestly.

The baby's sex is read reliably by medical means: a cell-free DNA blood test, which ACOG says can be done starting at 10 weeks, or the mid-pregnancy anatomy scan, which the NHS usually carries out between 18 and 21 weeks. Whether and when to have either is a conversation for you and your doctor or midwife. The gender prediction methods overview puts every folk and medical method side by side.