Mysteries have always surrounded the creation of new life. From two humans, a new one; from a woman's body, nourishment for a zygote, an embryo, a fetus, a newborn.
Every woman knows that how she takes care of herself during the months she's pregnant helps make a healthy baby. But now scientists are finding that prenatal and early-infancy influences may have a lifetime impact. "Genes are very important, but there's a whole new realm of research showing that experiences before birth can also shape health in a significant, long-standing way," says Lise Eliot, Ph.D., assistant professor of neuroscience at the Chicago Medical School.
New questions uncover new mysteries. Does a pregnant woman's behavior -- what she eats, whether she exercises, how she manages stress -- have permanent effects on her future baby? When sperm breaches egg, a genetic blueprint is written, but how that house is built greatly influences who the new person will be. It all begins before birth.
In pregnancy, then infancy, there are moments when certain factors -- nutrients, hormones, toxins -- can have a profound impact. Consider folic acid. If every woman of childbearing age had adequate amounts of this vitamin in her body, the incidence of neural tube defects, including spina bifida, would decline by 70 percent. Current efforts -- primarily fortification of flour with folic acid, which began in 1998 -- have already led to a 20 percent drop. While it's possible to get enough folic acid from diet alone, experts advise that every woman of childbearing age take a daily supplement of 400 micrograms.
But don't wait until you're pregnant. Folic acid needs to be present at the moment when an embryo's cells curve over one another to create the neural tube, between the 25th and 28th day after conception -- often before a woman knows she's expecting. A day late may be a lifetime short. "If the tube can't close, it can damage the entire central nervous system," says Mark Merkens, M.D., director of the Spina Bifida Program at Oregon Health Sciences University, in Portland.
That a simple pill could prevent most cases of spina bifida is remarkable. That the first recommendation for women to take folic acid came in 1992 shows how new the science is. What might we discover next?
A Delicate Beginning
Maybe we'll learn why women in the first trimester are often nauseated. We do know that can be a good thing: Those who experience the worst pregnancy sickness are at the lowest risk of miscarriage, stillbirth, or premature delivery. It's not clear why, although the queasiness may have evolved to keep women away from noxious foods that posed a threat to the fetus at a vulnerable time.
And vulnerable it is. First the spinal cord forms; then, in a matter of days, each organ appears. Within weeks, the embryo is a fetus, the length of a paper clip, with no further assembly required -- it simply grows bigger until birth. Writer Sandra Steingraber, Ph.D., in Having Faith: An Ecologist's Journey to Motherhood, describes the process: "Sometimes it seems like a magic show. At other times it's like origami, the formation of elegant structures from the folding of flat sheets."
Now's the time to heed those restrictive warnings: no smoking, alcohol, or drugs; no prescription, over-the-counter, or herbal medications unless specifically allowed. It's best not to:
- Paint the nursery (solvents; in an old house, lead)
- Use pesticides at home or in the garden
- Change your cat's litter (toxoplasmosis, from cat feces)
- Eat soft cheeses or deli meats (listeria -- food poisoning).
Above all, be vigilant about protecting yourself from infections, such as the flulike cytomegalovirus, or sexually transmitted diseases. "It's important to work closely with your obstetrician," says Donald Mattison, M.D., former medical director of the March of Dimes. "Call up, for example, even if you have only a slight fever."
What other critical moments might those nine months hold? Could a woman's healthy pregnancy open the window to her child's smarts or emotional equilibrium or the prevention of disease?
A Nice, Fat Brain
By the middle of the second trimester, the fetus's main work is to grow a bigger body and brain. "Fetal brain cells at six months are like saplings -- tiny little branches," says Eliot. "As they massively move out, a child's brain turns on."
To build the brain, fetuses and babies need many things, including a unique kind of fat called docosahexaenoic acid (DHA), an omega-3 fatty acid found primarily in fish. Not only does DHA help grow the branchlike dendrites, but it's also an essential component of myelin, an insulating sheath around nerve cells. "Myelin speeds up the rate at which our brains process information -- it's like going from a 486 to a Pentium 4," says Eliot.
"The brain triples or quadruples during the third trimester, and these fatty acids are uniquely concentrated in the brain during that period," says William Connor, M.D., professor of medicine and clinical nutrition at Oregon Health Sciences University. Experts recommend that pregnant women eat two servings of fish a week, including one fatty fish like salmon; vegetarians should cook with canola, flaxseed, or walnut oil; and anyone who can't do either should take a daily supplement containing one or two grams of omega-3 fatty acids.
You've finally reached the end of your pregnancy, and you're ready. How big will the baby be? How much will it weigh? You can think of the ideal as the Goldilocks standard: not too big, not too small.
An optimal birth weight, it's now thought, may set the stage not just for a healthier baby but for a healthier child and adult. Low-birth-weight babies -- those born at under five and a half pounds -- are at risk for many problems, immediate and long-term. But those born at over nine and a half pounds also risk being overweight as a child and an adult, says Mary Cogswell, a nurse-epidemiologist in the Maternal and Child Nutrition Branch of the Centers for Disease Control and Prevention, in Atlanta. Some of the risk may stem from having an overweight mother, researchers believe.
Prevention isn't simple, although gaining an appropriate amount of weight during pregnancy is part of the answer. Women who gain too much -- and 40 percent of pregnant American women do -- are more likely to have a too-heavy baby and to remain overweight themselves after giving birth. Excess weight gain also increases the risk of gestational diabetes, which ups a woman's chance of delivering a too-large infant. As obesity rates have risen over the past 20 years, so have rates of diabetes.
To gain 25 to 35 pounds during pregnancy, you need only about 300 extra calories a day. That's the equivalent of three extra glasses of skim milk. "Strive for a variety of fruits, vegetables, whole grains, dairy, and protein," says Tufts University nutrition professor Susan Roberts, Ph.D., coauthor of Feeding Your Child for Lifelong Health. "Limit unhealthy foods that encourage excess weight gain."
Tiny Infants, Chronic Ills?
Ironically, babies who weigh too little at birth may also be more prone to obesity and related problems later in life. In a long-term Harvard study of 70,000 nurses, women who weighed five pounds at birth were twice as likely to get heart disease as those who started life at ten pounds. Other studies have found that underweight newborns are more likely to have high blood pressure at 18 years and more likely to develop insulin resistance -- which increases the risk of diabetes -- as children. Epidemiologists suspect the fetus responds to undernutrition by becoming more efficient in its use of nutrients, which produces a child who is more prone to obesity and other metabolic problems later on.
Good nutrition during pregnancy may have multiple health benefits for mother and baby. But many other experts believe that the solution to optimal birth weight lies elsewhere. "Even if a mother eats well, she can have a small baby," says Roberts. One approach might be to reduce the rising incidence of prematurity -- since the 1980s, the preterm-birth rate has increased by 17 percent, according to the March of Dimes. But that's easier said than done.
Robert A. Barnett is Parenting's health editor.