Unless you're sure that you've had German measles or chickenpox or have been immunized against them, schedule a blood test to find out. Also get a flu shot and regular dental checkups (skip the X-rays, though); untreated gum infections are linked to premature births.
If you get sick, don't self-medicate: Even over-the-counter medicines such as aspirin as well as some "natural" and herbal remedies can be risky. Don't take anything that hasn't been OK'd by your doctor or midwife. (To find out if any substance you're considering taking or using is linked to birth defects, go to otispregnancy.org.)
6. Eat well (but not for two)
Pregnancy is the time to make every calorie count. "Choose foods rich in nutrients such as protein, folate, calcium and iron that will nourish you and your baby," says dietitian Heather Blazier. High-fiber foods, including fruits, vegetables and whole gains, can help prevent constipation, a common problem during pregnancy. So can drinking plenty of water, which you also need to support your increased blood volume. Eating four or five mini-meals a day can help prevent heartburn and keep your blood-sugar (and, thus, energy) levels steady and prevent bingeing.
Avoid foods that can be dangerous during pregnancy, including undercooked meats, cold cuts and deli meats; raw fish and oysters; raw or undercooked eggs; and large fish, such as shark, marlin, swordfish and tuna, which can contain high levels of mercury and other toxins. Limit your caffeine consumption to 150 milligrams daily, the equivalent of about 1 1/2 cups of coffee.