Fetus to Mom: You're Stressing Me Out! (cont.)
Most recently, some studies are suggesting that stress in the womb can affect a baby's temperament and neurobehavioral development. Infants whose mothers experienced high levels of stress while pregnant, particularly in the first trimester, show signs of more depression and irritability. In the womb, they also are slower to "habituate" or tune out repeated stimuli -- a skill that, in infants, is an important predictor of IQ.
"Who you are and what you're like when you're pregnant will affect who that baby is," says Janet DiPietro, a developmental psychologist at Johns Hopkins University. "Women's psychological functioning during pregnancy -- their anxiety level, stress, personality -- ultimately affects the temperament of their babies. It has to ... the baby is awash in all the chemicals produced by the mom."
The Womb Is a Busy Place
So, how does a mom's stress get passed onto her fetus? Researchers aren't exactly sure which stress responses play the largest role, but it's clear that when a pregnant woman experiences anxiety, her body produces chemicals that affect the baby, too. Her nervous system, for instance, stimulates the release of epinephrine and norepinephrine, stress hormones that constrict blood vessels and reduce oxygen to the uterus.
Since a very significant decrease in blood flow is probably necessary to compromise development of the fetus, Dr. Wadhwa says that another stress response is more likely to affect fetal growth and pre-term labor. That is, when pregnant women experience stress, particularly in the first trimester, the placenta increases production of corticotropin-releasing hormone (CRH), which regulates the duration of pregnancy and fetal maturation.
CRH is one of the most exciting recent scientific discoveries that could explain why women go into labor when they do. Called the "placental clock," CRH levels measured in the mother's blood early in pregnancy -- between 16 and 20 weeks -- can predict the onset of labor months later. Those with the highest levels will likely deliver prematurely, and those with lowest levels are apt to deliver past their due dates.
And it appears that stressful events occurring during the first trimester are most critical in signaling early labor. "That's very important because it used to be thought exactly the opposite -- that women become fragile as term approaches. Indeed, our data suggests that women become psychologically stronger," says Dr. Curt Sandman, professor and vice chairman of the department of psychiatry at University of California, Irvine.
Monitoring CRH levels and managing stress that early in pregnancy may have important implications in reducing pre-term delivery, says Dr. Christine Dunkel-Schetter, a professor of psychology at UCLA. Dr. Dunkel-Schetter is working on two studies (one with Drs. Wadhwa, Hobel and Sandman) to determine who is at highest risk for pre-term birth and what types of stresses are the biggest contributors.