Birth Defects
Eating Right for Two
Conception is the quick and easy part. From then on, the fertilized egg has to go through an intricate nine-month-long process of cell growth, division, migration and specialization, all geared toward producing a living, breathing bundle of joy.
That single fertilized egg cell must grow and divide to produce several billion cells. At the same time, all of the individual cells being formed receive directions to move toward specific regions of the embryo, perhaps where an arm or an eye will be. They also receive signals to differentiate, so some become, say, nerve cells, while others become bone cells. The process is complicated enough that it's a wonder couples turn out as many perfect babies as they do.
When things do go wrong, it's due to any number of different factors. Doctors now know that certain drugs, x-rays, exposure to environmental toxins, infections such as German measles and inherited genetic abnormalities can all cause a wide range of birth defects if the embryo is exposed at certain critical stages of development. So, too, can nutritional shortages.
"What percentage of birth defects in humans is associated with nutritional deficiencies isn't known," says William McGanity, M.D., professor of obstetrics and gynecology at the University of Texas Medical Branch at Galveston. "In about half of all cases of birth defects, however, the cause is not known, and in many of those cases, poor nutrition is believed to be one of the factors, either acting directly or interacting with other factors."
Nutrients such as protein, calcium, magnesium, iron and folate (the naturally occurring form of folic acid) are literally the building blocks for a new being.
"Studies of animals have confirmed that a severe shortage of any one of several different vitamins can lead to birth defects," Dr. McGanity says. These vitamins include thiamin, riboflavin, niacin, pantothenic acid, folate and vitamins A, B6, B12, C, D, E and K. Shortages of these nutrients are known to cause a wide range of birth defects in animals, including cleft palate, hydrocephalus (water on the brain), Siamese twins and kidney, limb, eye and brain malformations.
So far, however, deficiency of only one vitamin, folate, has been firmly linked to human birth defects, Dr. McGanity says. Whether any other vitamin will prove to play as crucial a role as this one remains to be seen. "Right now there doesn't seem to be any other nutrient that has as small a margin of safety as folic acid," Dr. McGanity says.
Here's what research shows.
Folic Acid: Right from the Start
As early as 1965, researchers suggested a relationship between folate deficiency and major central nervous system problems. That connection was suspected after reports of very serious birth defects in babies born to women taking anticonvulsant drugs that interfered with folate metabolism.
Those serious birth defects, called neural tube defects, are enough to turn the blessed event into a nightmare.
In a developing baby, the neural tube is a fold of tissue running the length of the embryo. This tube is what develops into the central nervous system, or the brain and spinal cord. When the neural tube fails to close at the top, the baby is born with only a very small brain or with no brain, Dr. McGanity says. The baby usually dies within a few hours or days.
When the neural tube fails to close at the base of the spine, the baby is born with a condition called spina bifida, a defective fusion of the vertebrae in the lower back. In severe cases, spina bifida causes crippling paralysis of the lower extremities.
It wasn't until the 1980s that the cause and effect really started to get nailed down. In two separate studies, researchers in Britain found that women who had given birth to one baby with a neural tube defect (which put them at high risk for having another) were much less likely to have a second baby with the same problem if they took folic acid supplements prior to becoming pregnant and during pregnancy.
In fact, in the high-risk group of the second study, the incidence of neural tube defects was cut by more than 80 percent.
Other later studies, in 1992 and 1993, showed that folic acid supplementation prior to conception could prevent first-time neural tube defects.
"Folic acid is important for fetal development because it's needed for the fetus to make DNA, the genetic material found in every cell," Dr. McGanity says. When it's lacking, cell production lags. "Requirements for this vitamin are much higher in the fetus than in the mother because of the rapid rate of cell growth and division," he explains.
Neural tube formation happens early in pregnancy, during the third and fourth weeks. Usually, that's about the time a woman first becomes aware that she's pregnant. "That's why it's important to start taking folic acid before you get pregnant," Dr. McGanity says. Studies show that folic acid offers the most protection when it's started at least three months prior to becoming pregnant and continued for at least three months into the pregnancy.
The results of these studies were strong enough for U.S. public health officials to make two recommendations.
First, they recommend that women who've had a baby with spina bifida take 4,000 micrograms of folic acid daily before and during pregnancy. (That is a very large dose and can be obtained only with a prescription.)
Second, they recommend that all women of childbearing age make sure to get the Daily Value of 400 micrograms of folic acid a day, even if it means taking a supplement to do so.
There's good evidence that many women aren't getting anywhere near 400 micrograms of folate a day from foods, say researchers at the University of California, Davis.
They found that even sensible eaters--those following the U.S. Department of Agriculture's Food Guide Pyramid, getting two to three servings of fruits and three to four servings of vegetables a day--consume only 190 micrograms of folate a day. (Public health officials are still debating the merits of fortifying foods with folic acid to increase intake, but the British aren't. They have already added it to cereals and other items.)
"I advise women to plan their pregnancies, to take folic acid supplements prior to conceiving and to continue for three months into their pregnancies in order to significantly reduce the chances of the fetus having a neural tube defect," Dr. McGanity says. You'll want to start taking folic acid supplements at least three months before you stop using contraceptives.
| Food Factors Eating for your baby means paying particular attention to eating right. Hop on the wagon. The devastating effects of alcohol on a developing fetus are now well-known. The best course of action is to plan your pregnancy and stop drinking all alcohol for at least a few weeks before you conceive, says William McGanity, M.D., professor of obstetrics and gynecology at the University of Texas Medical Branch at Galveston. And you should definitely lay off once you know you're pregnant. If you're having trouble stopping, get help. Fill up at the produce section. Early childhood brain cancer is rare, admittedly. But some preliminary research suggests that it may be linked to what a mom eats during the time she's pregnant, report researchers at the University of Pennsylvania in Philadelphia. They found that women who ate the most vegetables, fruits and fruit juices--two to three servings of each per day--and, accordingly, got higher amounts of vitamin C, beta-carotene and folate (the naturally occurring form of folic acid) were less likely to have children who developed early childhood brain cancers than women who ate few of these foods. "It's possible that in some cases, poor maternal nutrition may set the stage for the development of cancer in offspring," says the study's main author, Greta Bunin, Ph.D., professor of pediatrics at the University of Pennsylvania. In fact, one of these cancers, primitive neuroectodermal tumors, develops from cells that line the neural tube. This is the same area of cells found to be so dependent on adequate folate for proper spinal cord and brain development. Forget the franks. A study by researchers at three different cancer centers and hospitals in the United States found that the children of women who ate hot dogs at least once a week during pregnancy were more than twice as likely to develop brain tumors as children whose mothers eschewed franks. Although little is known about the cause of these childhood cancers, it is known that certain food preservatives and nitrites are converted to nitrosamines in the body, Dr. Bunin explains. "In animals, nitrosamines (N-nitroso compounds) have been linked to nervous system cancers," she says. |
| Prescriptions for Healing If you're pregnant or planning to become pregnant within the next year, you should see an obstetrician/gynecologist to plan your course. Why so far in advance? Because if you're overweight or underweight, you may need to lose or gain a few pounds. And if you have diabetes or some other chronic disease, you'll want to make sure it's well under control. You'll also want to start taking folic acid supplements three months before you stop using contraceptives. Here's what doctors recommend to help prevent birth defects. Nutrient Daily Amount
Folic acid 400 micrograms, 4,000 micrograms for women who've had a baby with spina bifida Pregnant women should also take these nutrients for general health. Nutrient Daily Amount Calcium 1,200 milligrams Iron 30 milligrams Plus a multivitamin/mineral supplement containing the Recommended Dietary Allowances for pregnant women
MEDICAL ALERT: While doctors routinely recommend iron supplementation for women who are pregnant, you should talk to your doctor before taking more than the Daily Value, which is 18 milligrams. A daily intake of 25 milligrams or more for an extended period of time may cause undesirable side effects. |
Taking a Little Insurance
Doctors say that pregnant women need extras of just about every other nutrient as well, including vitamin A, thiamin, riboflavin, vitamin B12, calcium, phosphorus, magnesium and iron. But dietary surveys indicate that mothers-to-be tend to come up short, consistently getting well below the Daily Values of seven nutrients: vitamins B6, D and E, folate, iron, zinc and magnesium.
That's why Dr. McGanity recommends a multivitamin/mineral supplement that includes no more than the Recommended Dietary Allowances for pregnant women. (There are no Daily Values for pregnant women.) "Use of a supplement as additional insurance is worthwhile and is not potentially damaging," he says.
Not all obstetricians recommend a multivitamin/mineral supplement, however. "Doctors working in the public sector of medicine are more likely to realize the potential benefits of supplements, since they see women who are at higher than normal risk for nutritional deficiencies," Dr. McGanity says. Most likely to be at risk: teenagers, vegetarians and women who are lactose-intolerant, who are having twins (or more!) or who smoke or use drugs or alcohol.
If your doctor doesn't recommend a multivitamin/mineral supplement, ask him about taking one, especially if you don't eat as well as you should, Dr. McGanity advises. Some doctors also recommend additional amounts of iron and calcium to prevent the anemia and bone loss that can accompany pregnancy. (The Recommended Dietary Allowances for pregnant women are 30 milligrams of iron and 1,200 milligrams of calcium daily.)
On the other hand, you don't want to overdo it with supplements. If you're taking large amounts of any vitamin or mineral, get your doctor's okay to continue before you become pregnant. Iron, for example, can cause undesirable side effects when taken in daily doses of 25 milligrams or more for an extended period of time.
In large amounts, fat-soluble vitamins A and D can cause birth defects. "During your pregnancy, you should get no more than twice the Recommended Dietary Allowances of these nutrients from foods and/or supplements," Dr. McGanity says. "If you're drinking plenty of milk and eating margarine and butter, you'll easily get the amounts you need of these nutrients without supplementation." In addition, women of childbearing age should talk to their doctors before taking vitamin A in daily doses of 10,000 international units or more.
