I had never heard this one. The only pregnancy prjudices I know about around here are (apart from the labour at full moon one) that the shape of the belly indicates if its a boy or a girl (and this one is correct in half the cases, so there must be something to it), and that if a pregnant women reaches above her (stretches her arms above the head), the umbilical cord will be around the neck of the baby.

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Knowledge is a curse, but ignorance is worse