lunes, 18 de octubre de 2010


Interesante artículo publicado en Scientific American con teorías curiosas acerca de la enorme influencia del embarazo sobre aspectos tan importantes como la posibilidad de desarrollo de enfermedades psiquiátricas, coeficiente intelectual, incluso de homosexualidad.

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 IQ scores.

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 amongoffspring. 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 womb. 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 his 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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