The Top 7 Pregnancy Myths

Can you color your hair? Get a flu shot? Have sex? Experts clear up your biggest concerns.

Medically Reviewed by Jennifer Robinson, MD on August 11, 2016
6 min read

When you're pregnant, you're likely to hear a lot of old wives' tales -- some of which can be amusing. You've probably heard this one: Carry high, it's a girl. Carry low, it's a boy. (Sure, it's silly, but our foremothers didn't have ultrasound.)

Not all pregnancy myths are entertaining though. Some prompt unnecessary worry while others can pose real health complications for mother or baby.

Just the opposite. "Flu vaccination is very important," Nancy Chescheir, a clinical professor of maternal/fetal medicine at the University of North Carolina at Chapel Hill, says.

Some pregnant women worry the vaccine might give them the flu. Others fret that preservatives in the vaccine may hurt their unborn baby. But a flu injection won't give women the flu, Chescheir says, nor is there any evidence that flu vaccine harms fetuses.

Instead, a flu shot can be a lifesaver for mother and baby. Pregnancy alters a woman's immune system, heart, and lungs, making them more vulnerable to getting a severe case of flu. "Women who are pregnant and come down with the flu do not tolerate it well and have a much higher risk of becoming extremely sick and a higher risk of dying from the flu than the general population," Chescheir says.

But get the flu shot (containing killed virus), not the nasal spray vaccine (containing weakened, live virus). And seek out a thimerosal-free flu shot if you’re worried about preservatives.

Helping yourself to double servings of potato salad or ice cream? Not so fast. Yes, you're eating for two -- but that doesn't mean two adult-sized servings are necessary.

The average woman with a normal weight pre-pregnancy needs only about 300 extra calories per day to promote their baby's growth, according to the American Congress of Obstetricians and Gynecologists (ACOG). That's roughly the number of calories in a glass of skim milk and half a sandwich. A woman of normal weight should gain 25 to 35 pounds during pregnancy -- less if they're overweight.

It’s difficult to drop extra pregnancy pounds after birth, Chescheir says. And with each subsequent pregnancy, a woman might become even heavier.

Also, women who gain more than 50 pounds when they're carrying just one child have a higher risk of a cesarean section or a difficult vaginal birth, Chescheir says. And babies who are "overgrown" at birth, she says, are more likely to be obese when they're adults.

No need to sport dark roots with your maternity wardrobe. Chemicals from hair dye, permanents, and relaxers are absorbed through the skin only in minimal amounts that aren't harmful.

"We don't believe there's any fetal risk from hair dyes and such," Chescheir says. But strong odors from hair treatment products make some pregnant women feel nauseous. So use them, she says, in a well-ventilated space with a fan.

You can hold off on hair treatments until you've passed your first trimester if you’re really worried. You can also avoid dyes with ammonia, which has strong fumes. "Hair changes a lot during pregnancy," Chescheir says. Products that worked well before pregnancy might not give the same results.

Do you love your morning cup of coffee? Many pregnant women do, but often they're warned to give up caffeine because it might cause miscarriage, preterm birth, or low birth weight.

But the case against caffeine isn't strong. "There does not appear to be any relationship between caffeine consumption and preterm birth," Chescheir says. Also, if a pregnant woman drinks less than 200 milligrams of caffeine per day -- the amount in about one 12-ounce cup of coffee -- there's no clear evidence they face any increased risk of miscarriage or low birth weight. So be prudent, Chescheir says. Enjoy your java, but stay within the recommended limit per day.

Airport body scanners, X-ray machines at security, radiation from flying at high altitudes -- think about all that and pretty soon, a staycation sounds awfully tempting.

But don't worry about the small amounts of radiation that pregnant women might encounter while passing by or through an airport X-ray machine or flying at high altitudes, Chescheir says. "We get exposed to radiation all the time from being on the ground, and certainly flying increases that a bit. But the kind of radiation you're exposed to [during air travel] doesn't have much penetration into the body, so it's unlikely to ever cause fetal exposure at all."

Nor are body scanners dangerous. "It's a very minute amount of radiation, and it's extremely unlikely to cause any sort of fetal effects," Chescheir says. Research evaluated by the FDA, the National Institute for Standards and Technology, and the Johns Hopkins University Applied Physics Laboratory back up her views. But "because there's a completely safe alternative," she says, "I would recommend that [pregnant] women get the pat-down. If they don't want to do that, they should be reassured that going through the body scanner should be fine."

If you're planning to fly in your last trimester, check with your airline about any restrictions. "Most airlines get a little anxious if you look like you might deliver en route," Chescheir says.

Some pregnant women should never fly without a medical clearance first. "Women who have coexisting lung or cardiac problems when they're pregnant might find they don't do well flying at 30,000 feet," Chescheir says. "They should ask their doctor before they get on a plane, but an otherwise normal, healthy woman should be able to fly very safely."

Eating two servings of fish per week can be healthy for mom and baby. Coldwater fish in particular contains lots of omega-3 fatty acids, which help with your baby's brain development and vision.

You should try to avoid fish high in mercury, such as swordfish, shark, tilefish, and king mackerel, Chescheir says. Salmon, shrimp, and canned light tuna are better choices.

Skip raw fish too, including sushi or sashimi, according to ACOG. Raw fish is more likely than cooked fish to contain parasites and bacteria. It's fine, however, to eat cooked sushi.

You can still have sex when you're pregnant. Sex doesn't physically hurt the baby, who is fully protected by the amniotic sac and strong uterine muscles. A thick mucus plug also seals the cervix. But you still need to watch out for sexually transmitted infections -- pregnancy doesn't protect against that. If you get herpes, genital warts, chlamydia, or HIV, the disease could be transmitted to your baby too.

Some women wonder if an orgasm can cause a miscarriage. If you have a normal, low-risk pregnancy, don't concern yourself: Contractions from orgasm are completely different from the type that's associated with labor.

Check with your doctor to make sure your pregnancy is indeed low-risk. Your doctor may advise against intercourse if there's any threat of miscarriage or preterm labor or if there's unexplained vaginal bleeding during pregnancy.