Slide Show: 7 Myths about Pregnancy
A look at the science (or lack thereof) behind prenatal wives' tales
Slide Show: 7 Myths about Pregnancy
- WOMEN EAT MORE WHEN EXPECTING A BOY: In 2003 a team of researchers from the U.S. and Europe studied the diets of 244 pregnant women during their second trimester and found that those carrying male fetuses ate, on average, 190 more calories per day than those carrying females. Those extra calories apparently made a beeline for the fetus, because the boy babies were heavier and their mothers did not pack on any more pounds than those carrying girls. "We found that birth weight of boys was on the average higher than that of girls," says senior author Dimitrios Trichopoulos, an epidemiologist at the Harvard School of Public Health in Boston. "Our interpretation is that boys are somehow programmed to be heavier than girls, and this requires higher caloric intake from the mother," he adds, speculating that testosterone from the fetal testicles might be involved in increasing the maternal appetite. EYELIAM VIA FLICKR
- LIFTING HEAVY OBJECTS COULD CAUSE THE PLACENTA TO RIP FROM THE UTERINE WALL: Lifting something cannot not cause the placenta to shear from the wall of the womb, cutting off the supply of nutrients and oxygen to the fetus, Saade says. The concern with lifting, he says, is that the mother could injure her back or lose balance and topple over. Being pregnant, especially during the final months, is like carrying a bag full of groceries all day—extra weight in the front that shifts the woman's center of gravity and makes it harder to balance, thereby putting stress on the spine, along with increasing her risk of falling. Lifting something heavy only adds more to that stress, Saade notes, upping the chance of back injuries such as pulled muscles. © ISTOCKPHOTO.COM/MEVANS
- A FETUS WITH A FULL HEAD OF HAIR SPELLS HEARTBURN FOR MOM: A few years ago, researchers from Johns Hopkins University (J.H.U.) in Baltimore decided to put this myth to rest with a scientific study, but they didn't get the results they were expecting. The researchers asked 64pregnant women—all in their third trimester—to rate the severity of their heartburn, and then compared the hair volumes of their infants within two weeks of birth. Their findings, published in the journal Birth: 23 out of 28 (82 percent) of the women reporting moderate or severe heartburn gave birth to babies with average or above average amounts of hair; only 11 out of 36 (31 percent) of those with mild or no heartburn produced babies with luxuriant locks. Study co-author Janet DiPietro, a developmental psychologist at the J.H.U. Bloomberg School of Public Health, cautions that the study was small and does not establish a definitive link between heartburn and fetal hair. But if there is one, she suspects pregnancy hormones such as estrogen and progesterone might be to blame. She says the same hormones that stimulate fetal hair growth might also relax the esophageal sphincter, the muscle in the esophagus that normally tightens after meals, allowing stomach acids to flow up into the esophagus and cause heartburn (acid reflux). VIRTUALERN VIA FLICKR
- PREGNANT WOMEN SHOULD AVOID PEANUTS BECAUSE THEY UP THE BABY'S ODDS OF DEVELOPING AN ALLERGY TO THEM There is no compelling scientific evidence that eating peanuts, shellfish or other potentially allergenic foods during pregnancy affects the baby's risk of developing allergies, according to Aziz Sheikh, a community health scientist at the University of Edinburgh in Scotland who has studied childhood allergies. U.T.M.B.'s Saade concurs. "For an allergen to affect the baby during pregnancy," he says, "it has to get into the mother's [blood] and then cross the placenta in a form that remains allergenic." But, he notes, the mother's metabolism might break down food allergens into nonallergenic components (such as amino acids and short chains of amino acids) before entering her bloodstream and reaching the fetus. EUROMAGIC VIA FLICKR
- BUMP IN THE FRONT? IT'S A BOY: If the fetus is male, the mom carries most of the weight low and in the front, like a basketball shooting from her hips; if it's a girl, the mother looks more like a planet, round all over—or so they say. "That's clearly a myth," says George Saade, chief of maternal-fetal medicine at The University of Texas Medical Branch (U.T.M.B.) in Galveston. How much the belly sticks out depends largely on how far the abdominal muscles flanking the left and right sides of the belly separate and relax, leaving a gap without muscle through which the uterus can bulge forward under the skin, Saade explains. And how high or low the belly sits depends on how much the pelvic joints loosen (thanks to a hormone called relaxin, produced by the ovaries mainly during pregnancy), thereby making more room for the baby to drop into the pelvis, he adds. Another factor influencing belly shape, he says, is the position of the fetus, which varies throughout pregnancy. The belly will appear wider, for instance, if the fetus is lying horizontally rather than vertically. © ISTOCKPHOTO.COM/TOMAZL
- FAT PREGNANT WOMEN ARE MORE LIKELY TO HAVE OVERWEIGHT BABIES: According to Robert Zurawin, an obstetrician–gynecologist (ob–gyn) at Baylor College of Medicine in Houston, overweight or obese mothers-to-be are more at risk than normal-weight ones of having big babies. The reason, he says: heavy women are more likely to have type 2 diabetes or to develop gestational diabetes (which occurs during pregnancy and usually passes after the baby is born). These diseases, in which the body has trouble using the hormone insulin, hinder cells' ability to absorb glucose, their primary energy source. As a result, the mom's blood contains excess glucose (also called high blood sugar), which passes to the fetus via the placenta, says Zurawin, adding "It's like the baby's eating ice cream all day long." © ISTOCKPHOTO.COM/KATE_SEPT2004
- ONLY THE MOTHER'S BIOLOGICAL CLOCK MATTERS: Wrong. Sorry guys, but you have biological clocks, too. Scientists have long known that a woman's advancing age brings decreased fertility and increased risk of having a baby with chromosomal disorders such as Down's syndrome, says Joshua Copel, an obstetrician–gynecologist at Yale Maternal-Fetal Medicine in New Haven, Conn. (The odds of a woman under 30 having a Down's child is less than one in 1,000, but by the time she is 35, it increases to one in 400; and when she reaches 42, her chances are one in 60, according to the National Institute of Child Health and Human Development.) Men can produce sperm throughout their lives, which means they can father children at any age. But there is evidence that older dads are also more likely to pass on genetic defects to their offspring, according to Copel. Studies suggest that 2 percent of infants with dads age 50 or older will develop the neurological disorder schizophrenia—that's three times the incidence among kids fathered by men in their early 20s. And some research suggests that fathers age 40 or older are six times more likely than those under age 30 to have kids with autism spectrum disorder. © ISTOCKPHOTO.COM/CHRISTIAN ANTHONY
