For a recent video, I interviewed 10 moms around the world on what it’s like to be them. Their answers varied widely, but moms in several nations had an unusual superstition in common:

During pregnancy, “if you have a food craving, and you don’t fulfill that craving, and you scratch yourself, your child will be born with a beauty mark in the shape of the food you were craving,” one mom in Israel told me. The mark would appear, naturally, on the part of the body the woman scratches.

Moms in Egypt, Brazil, and Italy had also heard of this, though not all of them put stock in it.

Which raises the question: How did a belief so strange become so well-traveled?

It’s not clear who started this particular myth, but it seems rooted in a broader set of ancient ideas that attributed birth anomalies to a mother’s experiences while pregnant.

For example, according to Edwin and Mona Radford’s The Encyclopedia of Superstitions, “if a pregnant woman meets a hare, the baby will have a hare-lip (cleft palate) ... the fear inspired by such an encounter was heightened by the idea that the hare might not be the innocent animal it seemed, but instead a witch in that form.”

Ancient physicians thought birthmarks, likewise, were the work of “maternal impressions,” or the mother’s emotional state during pregnancy, according to Boston Children’s Hospital:

Greek physician Galen believed that a pregnant woman need only look at an image of someone and her child might resemble that individual. This could be used to advantage by gazing at statues one admired, a practice that was sometimes encouraged to produce attractive children, but it could also have the opposite effect. According to Ambroise Pare, a surgical giant of the Renaissance, pregnant women who were exposed to or even imagined alarming sights risked giving birth to malformed infants.

The theory stuck around until the mid-1700s, when William Hunter, a Scottish anatomist, and his brother John, a surgeon, began to disprove it. John Hunter found that a mother and her unborn fetus do not share a blood supply, the path through which the mother’s emotions were thought to be transmitted. (Yes, they were wrong about that, too, but ... baby steps.) Still, some doctors continued to believe in maternal impressions for centuries, based on anecdotes of patients who, say, saw a house burning and bore a child with a vaguely flame-like scar on her forehead. One 1992 paper, by the admittedly discredited psychiatrist Ian Stevenson, noted that studies on maternal impressions were still being published into the 1900s.

Of course, if expectant parents worry their child will come out resembling Gorbachev (okay, a very cute Gorbachev), they have very little control over the matter. Birthmarks can be hereditary, but some just happen. And they obviously have nothing to do with the mother’s diet or unmet longings. Vascular birthmarks, such as port-wine stains, arise from overgrowths of blood vessels. Pigmented birthmarks, such as moles, are caused by clusters of darker skin cells.

The old wives’ tales have left their own mark on many different cultures. In several languages, including Italian and Spanish, the word for birthmark means “cravings.” In Dutch and Danish, the term includes the word “mother,” suggesting that only one parent could be responsible for the spots.

Stuart Vyse, a psychologist who has studied superstition, said the cravings myth might have lasted for so long because “superstitions are commonly associated with big life events—things that are highly anticipated and where there is much at stake. Weddings and births are such events.”

And enduring superstitions also benefit from what Vyse calls “random noise”—like the inexplicability of a strawberry-shaped splotch—that people can try to make sense of. (“Honey, remember that time I was craving fresh strawberries in the dead of winter?”)

“Finally, this superstition probably has become popular in part because it provides an additional justification for indulgence,” Vyse added.

After all, you wouldn’t want a baby with a chicken-and-Jello shaped mole, would you?