In fact, women who reported more stress and anxiety during pregnancy tended to have children more advanced in their mental and motor development at age two, according to developmental psychologist Janet A. DiPietro, Ph.D., of Johns Hopkins.
These results are at odds with those of previous studies in animals and humans, Dr. DiPietro and colleagues wrote in the May/June issue of Child Development. However, the results do not suggest that women should seek out extra stress in hopes of giving their child a developmental boost, they added.
Previous studies with contrasting results may have relied too heavily on pregnant women's self-reports of anxiety, stress, and depression, Dr. DiPietro and colleagues suggested.
The study involved 137 healthy pregnant women with low-risk normal pregnancies. Women who enrolled in the study tended to be more educated than average. The investigators assessed levels of stress, anxiety, and depression in these women during mid-pregnancy, six weeks after birth, and two years later. The women's children were assessed by a battery of developmental tests at age two.
After controlling for known confounders, a mother's anxiety level during pregnancy was significantly and positively associated with the child's mental development (Pearson correlation coefficient=.29; P<.01) and motor development (Pearson correlation coefficient=.28; P<.01).
Similarly, a mother's stress level was also positively associated with mental development (Pearson correlation coefficient=.22; P<.05) but not motor development (Pearson correlation coefficient=.12; P=ns).
Elevated, though still normal, levels of depression were also positively associated with mental development (Pearson correlation coefficient=.26; P<.05) and motor development (Pearson correlation coefficient=.23; P<.05), the study found.
Furthermore, these children did not appear to be affected temperamentally by their mothers' anxiety, stress, or depression during pregnancy, according to the 26-item Infant Behavior Record, designed to measure attention, social behavior, and positive affect, the investigators said.
"While these findings may seem counterintuitive, chemicals that are produced by stress have a well-known influence on organ growth and development," Dr. DiPietro and colleagues said. "Mild to moderate stress has been proposed to be important to successful adaptation to the environment after birth and necessary for optimal brain development."
However, these results definitely do not suggest that pregnant women should seek out stress, Dr. DiPietro said. The message from clinicians to pregnant women should be that, overall, an excessive amount of stress is not good for you, "and you should not go into the challenges of birth and taking care of a baby exhausted," she said.
It is also important to note that none of the women in the study had clinically significant levels of stress, anxiety, or depression, Dr. DiPietro said.
"These women experienced the typical types of stresses and anxieties that accompany juggling the many roles and responsibilities of modern life," she said. "It is possible that the results might be different if the study had included women undergoing more chronic, physical, or severe turmoil."
Nonetheless, the findings should put many pregnant women's minds at ease and enable them to "stop worrying about worrying," she said.
- Reviewed by Zalman S. Agus, MD Emeritus Professor at the University of Pennsylvania School of Medicine
Child DevelopmentSource Reference: Janet DiPietro et al. "Prenatal distress and child development." Child Development 2006; 77:xx-xxx.