A stressed pregnant woman might put her infant at risk for cognitive problems later in life. But a mother's nurture could protect against this risk, a new study finds.
The research provides the first direct human evidence that fetuses exposed to elevated levels of the stress hormone cortisol, which possibly gets released in the mother's body when she's stressed out, could have trouble paying attention or solving problems as they grow up. But what may be more intriguing is that this negative link disappears almost entirely if the mother forges a secure connection with her baby.
Future studies are needed to confirm the findings, said study author Thomas O’Connor, a professor of psychiatry and psychology at the University of Rochester Medical Center in New York.
O'Connor and his colleagues recruited 125 pregnant women, who were at 17 weeks gestation on average, and took samples of their amniotic fluid so that stress hormones levels could be measured.
When their children reached 17 months of age, researchers tested cognitive abilities with puzzles, pretend play, and baby memory challenges.
They also watched the baby and mother interact. Using the Ainsworth "Strange Situation" test, which judges childrearing quality, the researchers categorized these mom-baby pairs as either showing secure or insecure attachment to each other.
Secure children will be able to explore their surroundings while their mother is around, and will be sad if the mother leaves and happy when she comes back. Insecure children do not explore as much, and exhibit other insecure behaviors, such as showing no emotion when the mother leaves or returns, or becoming very anxious when she goes away, yet resisting her affection upon reunion.
For the insecure mom-baby pairs, the moms who had higher prenatal stress-hormone levels were more likely to have kids with shorter attention spans and weaker language and problem-solving skills. But for kids who had secure relationships with their moms, any negative link between high prenatal cortisol exposure and kids' cognitive development was eliminated.
"Pregnancy is an emotional experience for many women, and there is already so much for mothers to be careful of and concerned about," O'Connor said. "It's a relief to learn that, by being good parents, they might 'buffer'’ their babies against potential setbacks."
The results agree with the theory of "fetal programming," the idea that events in the womb could prime the developing child for long-term health and developmental outcomes. Past studies, for instance, have found a pregnant mother's diet can sway a child's long-term risk for heart disease, diabetes and obesity.
However, the researchers note it is hard to tell whether high levels of stress hormone result from an anxious mother or are excreted directly from the fetus itself.
They hope to follow up with the children at age 6 to see the long-term effects of in-utero cortisol levels and parenting style. The tests would include imaging studies of the children's brains.
The results were published Feb. 25 in the journal Biological Psychiatry. The research was funded by March of Dimes and the National Institute of Mental Health.