One study in this field, by a Columbia University economist, Douglas Almond, looked at children who were born after the great flu pandemic of 1918. The pandemic lasted only about five months and infected about a third of pregnant women in America, so Mr. Almond compared those who had been exposed to it while inside their mothers with others born just before or after.

Ms. Paul quotes Mr. Almond as concluding, “People who were in utero during the pandemic did worse, on average, on just about every socioeconomic outcome recorded.” They were 15 percent less likely to graduate from high school, 15 percent more likely to be poor, and 20 percent more likely to have heart disease in old age.

Stress in mothers seems to have particularly strong effects on their offspring, perhaps through release of cortisol, a hormone released when a person is anxious. Studies show that children who were in utero during the Arab-Israeli Six-Day War of 1967 were more likely to have schizophrenia diagnosed as adults. And The Journal of the American Medical Association reported that Chinese born during the terrible famine from 1959 to 1961 were twice as likely to develop schizophrenia as those born at other times.

As for obesity, Ms. Paul describes several British scientists who fed pregnant rats junk food: doughnuts, marshmallows, potato chips and chocolate chip muffins. The offspring of those rats turned out to have a sweet tooth as well: they were more likely to choose junk food when it was offered and ended up 25 percent fatter than rats whose mothers were fed regular rodent chow.

This field of “fetal origins” is still in its infancy, but one implication is that we should be much more careful about exposing pregnant women to toxins, and much quicker to regulate chemicals that are now widely used even though they’ve never even been tested for safety. Professor Agin is particularly eloquent about the potential perils of lead, dioxins, PCBs, radiation and pesticides.

One study looked at Swedish children who were fetuses during the 1986 Chernobyl nuclear accident. The radiation exposure was very slight and did not seem to affect their physical health. But their cognitive abilities, especially in math, seemed affected, and they were one-third more likely to fail middle school.

The uncertainty in this field is enormous, but we have learned that a uterus is not a diving bell that insulates its occupant from the world’s perils. Chemicals like thalidomide and DES proved tragic for those exposed to them while in their mothers’ wombs. And it’s now high time to take a closer look at unregulated chemicals that envelop us  and may be shaping our progeny for decades to come.