Healthy Living, For Two

In “Origins,” Annie Murphy Paul explores current scientific thinking about how our lives are shaped by what happens to us in utero.

Tobacco, heavy drinking, illegal drugs, depression: We seem to grasp that these aren’t healthy for anyone, let alone a pregnant woman. But just what effect do the things that women inhale, consume and experience have on a fetus? In “Origins,” Annie Murphy Paul sets out to discover the answer. Along the way she explodes myths, reviews scientific evidence and explores the new frontier of fetal-origins research, the study of how we are shaped in utero by a combination of genes and environment.

Ms. Paul, who was pregnant with her second child as she embarked on the project, explores possible prenatal influences on everything from physical development to mental health. But “Origins” is most compelling when Ms. Paul discusses the harrowing effects of past ignorance, such as the treatment of morning sickness in the late 1950s with thalidomide, a drug later linked to severe birth deformities, and the use of diethylstilbestrol (DES) from the 1940s to the 1970s to prevent miscarriage—the drug was later found to cause higher rates of cancer and reproductive problems in the daughters of women who took it.

Ghastly though thalidomide and DES turned out to be, the problems they caused provided stark evidence of the intricate biological links between pregnant women and their unborn children. One researcher tells Ms. Paul that fetal-origins research means “extracting otherwise inaccessible scientific knowledge from the harsh soil of human catastrophe.”

A key to the evolving science is a major shift in thinking about the role of the placenta. The organ develops in female mammals during pregnancy, lining the uterine wall and partially enveloping the fetus; the umbilical cord connects the fetus to the placenta, enabling the flow of nutrients and the elimination of waste. Until modern times, the placenta was regarded as the perfect filter, protecting the fetus from harmful substances in the mother’s body and letting through helpful ones.

Such thinking has changed radically as evidence mounts that the placenta is not such a discerning filter after all. It does an impressive job of blocking bacteria from reaching the fetus, but studies show that it does not block other dangers known as teratogens—agents such as radiation, pathogens, drugs and chemicals that can cause malformation of the developing embryo.

But how worried should expectant mothers be? Anyone looking for definitive answers in “Origins” will be disappointed, because there aren’t many. Ms. Paul starts her quest in her first month of pregnancy, and it is a long slog from there to delivery. In each successive month, marked by the start of another chapter, she encounters new questions and potential minefields, and she sifts through real science and junk science. Over and over, she finds, the bottom line about what’s safe and what’s not is: “We just don’t know.” Eat fish? Yes, as long as the species isn’t exposed to mercury. Reduce stress? Yes, but remember that moderate stress levels may actually be good for the fetus, accelerating its maturation.

Even warnings about the ill effects of tobacco, alcohol and drugs taken during pregnancy are not clear-cut. As the series “Mad Men” reminds us, it wasn’t so long ago that pregnant women rarely modified their behavior with a fetus’s well-being in mind. In the heart of the baby-boom era, pregnant women were told it was fine to light up a cigarette and knock back a few drinks. Research has changed that view, of course. Smoking has been tied to miscarriage, stillbirth, premature birth, low birth weight and birth defects. Excessive alcohol use can lead to fetal-alcohol syndrome, which stunts development and can cause birth defects. Heavy drinking, surprisingly, is worse for the fetus than smoking crack cocaine; the “crack-baby epidemic” of terribly damaged infants, widely predicted in the 1980s, never materialized. Children exposed to cocaine in the womb do exhibit behavioral problems later in life, but a mother’s use of alcohol and tobacco is more damaging.

Then again: Pregnant women who smoke early in pregnancy can minimize damage to the fetus if they stop smoking by week 15. As for alcohol, the author cites studies indicating that children of women who were light drinkers during pregnancy—one or two alcoholic beverages a week—are less likely to suffer from emotional problems and hyperactivity than the children of women who shunned alcohol. But researchers also note that lighter drinkers tend to be better educated and from higher-income households than abstainers, and such factors may influence results.

“A reader venturing into this literature is liable to get whiplash,” says Ms. Paul. The readers of “Origins” may at times feel the same way. Yet with all the conflicting evidence, erring on the side of caution seems wise. When Ms. Paul tells one expert that she turned out fine even though her mother drank during pregnancy, he offers the unnerving reply: “Are you sure you’re fine? What could you have been if she didn’t drink?”

Ms. Paul does a commendable job of gathering in one place much of the literature on fetal-origins research. She discusses, for instance, concern about phthalates, a synthetic chemical used to make plastics more pliable. The evidence about its possibly damaging fetal development is not clear, but Ms. Paul chooses a prudent course. She throws away certain recyclables and makes a point of not putting the plastics in the microwave or dishwasher, where heat may release the chemical.

“Origins” also examines such matters as the possible influence of a pregnant mother’s depression on her unborn child’s later mental health. Ms. Paul visits Catherine Monk, a psychiatry professor at Columbia University, whose research suggests that the “intrauterine environment” may be one of the ways, in addition to genetics and parenting, that mental illness is passed from one generation to the next. The science remains unsettled—but on that front and many others Ms. Paul makes a persuasive case that fetal-origins research promises one day to bear valuable fruit.

Ms. Landro writes the Informed Patient column for the Journal.


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