When it comes to medical care and pregnancy, you can never start too early.

"The best start to having a healthy baby is to see your health-care provider before you conceive," says Richard Schwarz, M.D., an obstetrician and national consultant for the March of Dimes.

"There are lots of things you can do ahead of time," Schwarz adds. "You can make sure you're immune to rubella [German measles], you can know your blood type, you can stop smoking and make sure your diet is healthy, and you can get any illnesses you might have under control."

Once you're pregnant, your health professional--either an obstetrician, family practitioner, nurse-practitioner, or nurse-midwife--will have you begin with monthly visits that increase to once a week or more at the end.

At each visit, the physician or nurse will perform a series of examinations and tests to determine the health of the mother and baby. These include measuring the growth of the uterus, listening to the baby's heartbeat, taking the mother's blood pressure and weight, and checking her urine for evidence of protein or sugar, which could be symptoms of complications. The care provider will ask the mother if she has any concerns or problems such as blurred vision, leg cramps, abdominal cramps, or unusual headaches. The mother may also undergo ultrasound and genetic tests during the pregnancy.

Although prenatal visits may seem simple and even mundane, their importance can't be overestimated. Years of research have shown that pregnant women who get adequate prenatal care are more likely to have healthy babies and fewer complications during labor and recovery. Says Schwarz, "We know that pregnancy outcomes are better in women with early prenatal care."

Good nutrition is another crucial step in having a healthy baby. A pregnancy takes about 300 extra calories a day to maintain, and an average-sized woman can expect to gain between 25 and 35 pounds overall.

Those extra calories should be nutritious ones, however. A pregnant woman needs a balanced diet complete with protein, fruits, vegetables, and whole grains, and a minimum of sweets and fats.

"Good nutrition is extremely important even before a pregnancy," says Shirley Blakely, Ph.D., a registered dietitian with the Food and Drug Administration's Center for Food Safety and Applied Nutrition. "If nature favors the growing fetus, the mother will suffer if she hasn't had a good diet."

According to the March of Dimes, a pregnant woman should increase her daily food portions to include:

• 6 to 11 servings of breads and other whole grains
• 3 to 5 servings of vegetables
• 2 to 4 servings of fruits
• 4 to 6 servings of milk and milk products
• 3 to 4 servings of meat and protein foods
• 6 to 8 glasses of water, and no more than one soft drink or cup of coffee per day to limit caffeine.

Some nutrients have been found to provide specific benefit to mother or child. For example, the B vitamins have been found to be especially important. One of them, folate, or its synthetic form, folic acid, can reduce the risk of birth defects of the brain and spinal cord, called the "neural tube." (See "Folic Acid Awareness." )

Each year, an estimated 2,500 babies are born with neural tube defects. The most common of these is spina bifida, in which the spine is not closed. The exposed nerves are damaged, leaving the child with varying degrees of paralysis, incontinence, and sometimes mental retardation.

Because neural tube defects develop in the first 28 days after conception, "Once you know you're pregnant it's too late to do anything about [them]," says Blakely.

Because half of all pregnancies are unplanned, the U.S. Public Health Service recommends that all women of childbearing age get 400 micrograms of folic acid each day. If all women received that amount daily, the incidence of neural tube defects might be reduced by an estimated 45 percent, studies suggest. To help reach this goal, FDA now requires that all flour products, such as breads, buns and bagels, be fortified with extra folic acid.

Natural sources of folic acid include green leafy vegetables, nuts, beans, and citrus fruits. It's also in many fortified breakfast cereals and some vitamin supplements.

Calcium and iron are also especially important during pregnancy. Getting enough calcium will help prevent a new mother from losing her own bone density as the fetus uses the mineral for bone growth. Iron helps both the mother and baby's blood carry oxygen. Most women need supplements to maintain adequate levels of these minerals. A daily vitamin supplement, while not an adequate substitute for a healthy diet, helps fill in the gaps on days when a woman's diet is less than perfect.

Many infections during pregnancy can be dangerous to an unborn child. Urinary tract infections and any sexually transmitted diseases need to be treated immediately.

Cat litter and raw meat may contain the parasite Toxoplasma gondii , which can cause toxoplasmosis infection . It's rare for a pregnant woman to get the infection, but if she does, her baby could be at risk for serious illness or death. Get someone else to change the kitty litter if possible, or wear a face mask and rubber gloves for protection.

Problems also may arise when a pregnant woman eats undercooked or raw foods, or cooked foods that have been cross-contaminated with bacteria from raw food nearby. Food poisoning can cause meningitis, pneumonia, or even death to an unborn child, plus the vomiting and diarrhea involved leave the mother exhausted and dehydrated. (See "On the Home Front" in the November-December 1997 FDA Consumer.)

Nearly everyone knows pregnant women shouldn't take illicit drugs, but it's the legal ones--alcohol and tobacco--that are more commonly the source of pregnancy problems.

"I think if women truly understood the adverse impact smoking and drinking have on their babies, they would quit," says Jeffrey King, M.D., the director of the division of maternal and fetal medicine at Wright State University School of Medicine, and the author of a recent study on substance abuse in pregnancy.

Smokers put their babies at a significantly higher risk of preterm birth, low birth weight, and stillbirth compared with nonsmokers. After birth, the babies of mothers who smoked during pregnancy are more likely to have poor lung development, asthma and respiratory infections, and to die of sudden infant death syndrome (SIDS).

If a woman quits smoking early in pregnancy, however, she can still improve her chances of having a healthy baby. Expectant fathers or other members of the family should quit, too, because studies suggest breathing second-hand smoke may be dangerous as well.

Alcohol, too, can damage a developing fetus. Alcohol travels rapidly to the bloodstream, so when an expectant mother drinks, her baby drinks also.

Alcohol is known to cause mental retardation and facial abnormalities in babies, a condition called fetal alcohol syndrome. The Institute of Medicine estimates some 12,000 children with fetal alcohol syndrome are born in the United States each year. No one knows what amount of alcohol is safe during pregnancy; therefore, the U.S. Surgeon General recommends pregnant women avoid alcohol altogether.

A few other activities are known to be dangerous during pregnancy. X-rays can expose the fetus to radiation and potentially cause birth defects. Hot tubs and saunas can raise the core temperature of a pregnant woman's body and could potentially harm the fetus. Warm baths, however, are fine if the water is kept at body temperature.

Exercise

There's increasing medical evidence to show that exercise, even a vigorous workout, is healthy during pregnancy. An October 1998 study published in the American Journal of Public Health found that exercise is usually safe during pregnancy, and that women who exercised vigorously were more likely to carry their babies to full term compared with women who exercised less or not at all.

A pregnant woman should check with her doctor before exercising, however. If she gets the OK to work out, she should do so at least three times a week for 20 minutes each time, recommends the American College of Obstetrics and Gynecology.

Walking, swimming, riding a stationary bicycle, and joining a prenatal aerobics class are all excellent exercise choices for a pregnant woman. Exercises that require jerky, bouncy movements and being outside in hot weather are not good choices. Don't try deep knee bends, sit-ups (or any exercise that requires you to lie on your back after the first trimester), and toe touches. Other sports to avoid include downhill skiing, rock climbing, and horseback riding.

Wear a supportive bra and properly fitting athletic shoes while exercising. Stop if you feel dizzy, faint, overheated, or in pain. Drink plenty of water.

Staying in shape will help you keep up your stamina during your own impending marathon--labor! And, afterward, the more muscle mass you have, the quicker you'll regain your pre-pregnancy shape and be able to pack away those maternity pants.