Pregnancy is a unique time with unique challenges. It's understandable to want to do all you can to deliver a healthy baby. But how do you decide what's best? Your own health care professionals can be an important resource, but what about things you read or hear between visits? You may not want to be calling your doctor to double-check everything.
Even for those things for which there's no answer, one thing's for sure: You'll get advice about it. No matter how popular, advice that is clearly wrong is worth ignoring. I searched the web, asked readers of Aetna InteliHealth, and surveyed my friends and family to come up with the list of myths below. As expected, the number of opinions about what pregnant women should and should not do was exceeded only by the confidence placed in these rules and prohibitions. Here's a sampling of what I heard:
The gender of your baby is determined by the father. More specifically, if sperm carrying an X-chromosome fertilizes the egg, the baby will be a girl and if the sperm carrying a Y-chromosome fertilizes the egg, a boy will result. The position of intercourse has no reliable effect on which type of sperm (X or Y) successfully fertilizes the egg.
The baby's size and position determine how one "carries" their baby. For example, during late pregnancy, the baby's head "drops" lower into the pelvis in preparation for delivery. That will make it seem as if the mother is carrying "low," but that happens for male and female babies. A mother-to-be may be carrying "high" simply because the baby is large, not because of its gender.
Most experts believe this is truly a myth. However, several studies have found that among women with morning sickness severe enough to require admission to the hospital, slightly more than half (53% to 56%) delivered girls. So perhaps there is some truth to this idea. Then again, even among those with the worst morning sickness, the male and female offspring were nearly 50-50 and whether this applies to milder cases is unknown.
No one knows exactly why morning sickness (also known as hyperemesis gravidarum) occurs, though it has long been thought to relate to elevated hormone levels, including progesterone, estrogen and/or human chorionic gonadotropin, or HCG. Which hormone, if any of these, is most important, remains a matter of speculation, and several other theories have been proposed such as zinc deficiency, low blood sugar, genetic factors and psychological factors. At least one study found that women carrying a female fetus had higher HCG levels than with a male fetus. If true, that could explain the connection.
Up to 25% of fetuses have the umbilical cord wrapped around the neck. It's the baby’s activity in the womb and, perhaps, bad luck, not the mother’s activities during pregnancy that determine whether the cord is wrapped around the baby’s neck. Another important risk factor is a long umbilical cord, but, again, that may have more to do with fetal activity and is not something a pregnant woman can prevent. The good news is that nearly all of these babies develop normally and are successfully delivered.
Heartburn is common during pregnancy because, as the stomach is pushed higher by the growing baby and the expanding uterus, it becomes easier for acid to move backwards (or "reflux") from the stomach into the lower esophagus. Acid is irritating to the esophagus and causes the discomfort we know as heartburn. Remaining upright after eating, sleeping with the head of the bed at a slight elevation, and antacid medications (many of which are considered safe during pregnancy) can be helpful. Check with your obstetrician before taking any medications during pregnancy, including over-the-counter remedies.
During the later stages of pregnancy, the uterus and baby may be large enough to press on the large vein, the inferior vena cava, and reduce flow of blood from the lower body (and uterus) back to the heart. But this tends to matter only in certain circumstances such as prolonged labor, if blood pressure is high, if the kidneys are not functioning properly, or if there is a problem with fetal development. In those situations, lying on the left side may be somewhat helpful, but for normal, healthy women in the midst of a routine, successful pregnancy, the best position for sleeping is the one that's most comfortable.
Within the bounds of common sense, there is no recommendation to avoid exercise or sex during pregnancy. The baby is protected in the uterus so that sex is unlikely to cause problems. Similarly, moderate exercise is not prohibited during pregnancy, and is often recommended. Because excessive body heat can be harmful to a developing fetus, exercising in hot weather should be avoided. And if your pregnancy is complicated by bleeding, pre-term labor or other problems, your obstetrician may recommend that you avoid sex as well as certain exercises.
This myth is close to the truth but still untrue. Recommendations regarding cats during pregnancy are due to concerns about toxoplasmosis, a parasite that can cause serious infections in humans and deformities in the developing fetus. Infection can follow the handling of cat litter because it can be found in the stool of cats. So pregnant women are advised not to handle cat litter. However, no other activities are prohibited — feeding or petting your cat and allowing it to sit in your lap are considered perfectly acceptable while pregnant, especially if your cat has been tested for toxoplasmosis. The risk of getting toxoplasmosis from your cat is quite low if your cat has tested negative for this parasite or is an indoor cat that eats only store-bought canned or dry food.
While unnecessary radiation exposure should generally be avoided while pregnant, if there is a good reason for a chest X-ray (for example), the amount of radiation exposure to the fetus is minimal — in fact, according to some experts, you might receive a similar amount of radiation by taking several commercial airplane flights (due to cosmic radiation from the sun and other stars). There is no evidence that modern microwave ovens or computer terminals expose women or their fetuses to harmful radiation.
Apparently, concerns about contracting an infection that could spread from the vagina, through the cervix, into the womb led to recommendations to avoid bathing. However, there is no well-established risk known to be associated with bathing during pregnancy. The water should not be too hot, since raising body temperature above 101 degrees F may cause problems. And there may be times to avoid bathing altogether, for example, if your water has broken or there is bleeding.
While believers may never be convinced otherwise, studies have demonstrated no increased incidence of labor based on the weather or the phase of the moon. Never mind the fact that even if this were true, there’s nothing you could do about it! In fact, labor is triggered by a complex series of hormonal signals with no known connection to atmospheric conditions or the weather.
As above, scientific evidence suggests that labor is triggered by biological signals, some of which are well understood while others remain uncertain. For a routine pregnancy, as long as you eat a well-balanced diet, there is no evidence that what you eat has any effect on your delivery date.
Minor bumps, taps and jolts, as in a bumpy (but “on-road”) car ride is highly unlikely to trigger labor. The uterus and surrounding fluid provide ample cushioning and protection from minor trauma. Of course, major injury, as in a car accident or a fall, may complicate pregnancy, including inducing pre-term labor.
You may hear these myths or others during your pregnancy, or you may even be the one disseminating these well-meaning but misguided warnings. Understand that there may be some elements of truth to some of these. For example, certain types of cat exposure may increase the risk of toxoplasmosis, and you might be slightly more likely to have a girl if your morning sickness is severe. For most routine pregnancies, however, they can be safely ignored. Proving that a theory is true can be difficult, but disproving a myth can be impossible. Many of these have been ingrained in our culture and passed down through generations. If you read or hear something that concerns you about your pregnancy, talk with your doctor about it, especially if it contradicts something he or she recommended before.
There are only a few things known to matter in a routine pregnancy, above and beyond common sense. One need not live in fear of causing harm to your developing fetus for nine months, especially when the vast majority of routine pregnancies produce normal, healthy babies.
Robert H. Shmerling, M.D., is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.