The Brain–from Womb to Tomb
From IQ to mental illness, how prenatal life affects the brain
It was on the cover of The New York Times Book Review. And the cover of Time Magazine. Suddenly, the obscure science of “fetal origins” is getting popular, in the pages of a new book called “Origins: How the Nine Months Before Birth Shape the Rest of Our Lives.”
Written by science journalist Annie Murphy Paul, “Origins” explores the still-murky but growing research into how the environment in the womb can affect a baby’s life ever after — including the life of the mind. A few questions for the author:
Q; In “Origins,” you describe myriad ways that the prenatal environment appears to influence the fetus. What do we know about the effects of the womb on the brain?
A: Fetal origins is very much an emerging science, so we know less than
we would like about the effects of the prenatal environment on the
brain. We do know, of course, that the brain is formed during the nine
months of gestation, and that a number of influences during this
period–chemical exposures, stress, depression, drug and alcohol use,
nutrition–can have effects on the brain, showing up in things like
measures of neural conduction speed, tests of cognitive ability, and
Q: Many pregnant women worry that their own emotional state, particularly stress, will affect the fetus. How would you sum up the findings on that?
A: The findings on the effects of prenatal stress are twofold. It’s
fairly well established that traumatic stress–severe,
life-threatening stress, like that experienced in a natural disaster
or war–is associated with a higher risk of premature delivery, low
birth weight, and in some studies, birth defects. Chronic stresses
like those associated with poverty and discrimination may also have
deleterious effects. Moderate stress, however–the everyday hassles
experienced by your typical working woman or woman caring for other
children–actually appears to accelerate fetal brain development,
leading to faster neural conduction speed as infants and higher scores
on tests of cognitive ability as toddlers.
Q: And what is known about the possible origins of mental illness in the womb?
A: A number of studies on different populations suggests that severe
prenatal stress or malnutrition, particularly in the first trimester
of pregnancy, is associated with a higher risk of schizophrenia among
offspring. Higher rates of this mental illness have been found, for
example, in individuals whose mothers were pregnant during the Nazi
siege of Holland during World War II, during the famine that followed
China’s “Great Leap Forward,” and during the Arab-Israeli War of 1967.
A more speculative theory is that women’s own mental states of
depression or anxiety affect the offspring’s own likelihood of
developing mental illness, perhaps through the effects of the stress
hormone cortisol. Dr. Catherine Monk at Columbia University is doing
fascinating work, measuring the responses to stress exhibited by
fetuses of depressed and non-depressed women. She believes that
intrauterine conditions may be a “third way” that mental illness is
passed down in families, along with genes and parenting behaviors.
Q: One fascinating theory suggests that the womb may be the arena of a fight between the fetus’s heart and its brain for resources. How does that work?
A: A theory originally put forth by British physician David Barker (and
long known as “the Barker hypothesis”) proposes that when a fetus
receives insufficient nutrition, it will “make the best of a bad job”
by diverting most of the nutrients it does receive to the organ most
critical to its survival: the brain. This act of triage allows it to
survive to be born and perhaps even grow into middle age–but at some
point the early deprivation experienced by the heart and other organs
shows up in increased rates of heart disease and other illnesses.
Q: You mention that the prenatal environment may account for something like 20% of IQ. Really? And how best can we make smarter babies?
A: To be more precise, a study published in Nature by researcher Bernard
Devlin and his coauthors found that in their analysis of twin studies
of IQ, the intrauterine environment accounted for 20 percent of IQ
similarity between twins, and genes for only 34 percent. Devlin’s
point was that in drawing conclusions from such studies (which were
used to buttress the assertions in the book “The Bell Curve,” for
example), we must take into account not only genes and childhood
environment, but also the very FIRST environment that twins share: the
In terms of making smarter babies, the best advice to pregnant women
is to eat a wholesome diet, refrain from drinking alcohol and using
drugs, protect yourself from environmental toxins, and try to
alleviate excessive stress. There’s some preliminary evidence that
physical exercise by the pregnant woman may promote offspring’s
intelligence, and it can’t hurt. But forget about playing Mozart to
the fetus and other “prenatal education” products–they won’t increase
intelligence and may even be harmful.
Q: There’s also a theory that links the prenatal environment and homosexuality. How would that work?
A: It’s a well-established finding that homosexual men are more likely to
have older brothers. The theory–and it’s still speculative–is that
the body of a woman carrying a male child generates antibodies in
response to her fetus which stay on in her body after she gives birth.
When she becomes pregnant again with another male child, those
antibodies affect the developing brain of the fetus in ways that
incline the offspring towards homosexuality. It’s an intriguing theory
but one that needs a lot more substantiation.
Q: What do you say to mothers who protest that “fetal origins” research is just more reason for even more maternal guilt?
A: I would say, first: I totally sympathize. I was pregnant when I
researched and reported “Origins,” and I had to work through a lot of
my own anxiety and guilt. What I came to realize is that the science
of fetal origins is growing so rapidly that we are only going to hear
more and more about how prenatal conditions affect later health and
well-being–so we need to find a more positive and productive way of
thinking and talking about these findings, one that neither dismisses
them out of hand nor makes us crazy with worry. I also found the
excitement and optimism of the fetal-origins researchers I talked to
rather contagious: they see pregnancy as a scientific frontier, a
wonderful new opportunity to head off public health problems like
obesity and diabetes. So I came, over the months that I was writing
“Origins,” to see pregnancy in that light–as a physical, emotional,
and intellectual adventure.
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