In Origins, you say that exercising while pregnant makes babies healthier and smarter. Are concerns about overdoing it and harming the fetus unfounded?
Moderate exercise is very beneficial. When a woman works out, her fetus is getting a workout, too. Research suggests that women who exercise while expecting have larger babies who grow up to be smarter adults, perhaps because their brains are bigger. But if you're getting so winded you can't manage to gasp out a sentence, you're probably working out too hard. Pregnant women need to make sure they don't become dehydrated—so, drink a lot of water during and after exercise.
About 20 percent of pregnant women experience mood or anxiety disturbances, and at least 10 percent develop full-blown depression, according to your book. How does this affect the fetus?
Pregnant women who are depressed are more likely to deliver early and have babies with a low birth weight. The mother's emotional state can also influence the fetus's developing brain and nervous system, and potentially shape the way the baby will experience and manage its own emotions. Plus, babies born to depressed mothers are more likely to be irritable and have trouble sleeping. Pregnant women should be screened for depression, just as we screen for gestational diabetes.
Pregnant women are inundated with tips: Do this, but avoid that—until next week, when the advice changes. How can women become more savvy about what's worthwhile, and what they should approach more skeptically?
Women should read and learn as much as they can, and talk with their obstetrician. And remember that the fetus is resilient. We've been giving birth to babies for the entire history of humanity. If you're thinking about it and worrying about it, you're probably doing the best you can.
What's the single most important habit for pregnant women to adopt?
Nutrition. What a woman eats and drinks during pregnancy is so important—not only for her own health, but for the health of her offspring into infancy, childhood, and potentially even adulthood. Eat a well-balanced, healthy diet, with fruits, vegetables, whole grains, and fish. A lot of women are scared to eat seafood because of warnings about mercury, but it actually facilitates fetal brain development. Opt for kinds that are low in mercury: sardines, anchovies, tilapia, salmon, or shell-fish.