Paulson said many of the misconceptions about controlling a baby's sex come from a single book: the late Dr. Landrum Shettles' "How to Choose the Sex of Your Baby."
The book has sold more than 1.5 million copies and is the first source for the idea that male sperm are sprinters and female sperm are marathon runners.
"I'm not even sure what research this was based on, but because he was a doctor, people believed it," Paulson said.
Paulson has never seen research that could confirm this idea, or research proving that the methods in Shettles' book work, but he has seen plenty of patients who tried to change the odds for having a boy or a girl.
By the Shettles method, couples wanting a boy should try to conceive right after the woman has ovulated, presumably to give the faster, yet short-lived male sperm a better chance to get to the egg.
If a couple wants a girl, the Shettles method says to try to conceive a few days before the woman ovulates to let the male sperm die off and give the so-called heartier, yet slower, female sperm a chance to make it to the egg.
"This thing has absolutely percolated into the population and everyone believes it," said Paulson.
"Guess what? It doesn't work," he said. "There's never been one shred of evidence that it works."
Moore said she has heard many more myths about how to guess the sex of the baby after conception, including myths that suggest carrying high or low can predict the gender, and bad morning sickness means a baby girl.
"The other one that drove me crazy is if you had terrible indigestion, it's a girl, or the baby will have a full head of hair," said Moore.
"In the year 2009, the best way to tell if it's a boy or a girl is an ultrasound," said Moore.
Moore, who spent years working as an obstetrician, thinks awe, more than ignorance, fuels many of these pregnancy myths.
"As much science as we know about pregnancy and childbirth, it's all really unbelievable. It's a miracle," said Moore. "Every single time ( at birth), part of me was feeling like, 'there's no way a baby's coming out of there."
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