Stress during pregnancy manifests in numerous ways

Washington: Maternal stress not only affects fetus and child development but also has an impact on birth outcomes, claims a recent study. The study was published online in the journal -- PNAS, the Proceedings of the National Academy of Sciences.

"The womb is an influential first home, as important as the one a child is raised in, if not more so," said the study leader Catherine Monk, PhD, professor of medical psychology at Columbia University Vagelos College of Physicians and Surgeons and director of Women's Mental Health in the Department of Obstetrics & Gynecology at NewYork-Presbyterian/Columbia University Irving Medical Center.

Because stress can manifest in a variety of ways, both as a subjective experience and in physical and lifestyle measurements, Monk and her colleagues examined 27 indicators of psychosocial, physical and lifestyle stress collected from questionnaires, diaries, and daily physical assessments of 187 otherwise healthy pregnant women, ages 18 to 45.

The study suggested that pregnant women experiencing physical and psychological stress are less likely to have a boy. "Other researchers have seen this pattern after social upheavals, such as the 9/11 terrorist attacks in New York City, after which the relative number of male births decreased," said Monk.

"This stress in women is likely of long-standing nature; studies have shown that males are more vulnerable to adverse prenatal environments, suggesting that highly stressed women may be less likely to give birth to a male due to the loss of prior male pregnancies, often without even knowing they were pregnant," Monk added.

Other than this, physically stressed mothers, with higher blood pressure and caloric intake, were more likely to give birth prematurely than unstressed mothers. Among physically stressed mothers, fetuses had reduced heart rate-movement coupling -- an indicator of slower central nervous system development -- compared with unstressed mothers. And psychologically stressed mothers had more birth complications than physically stressed mothers.

The researchers also found that what most differentiated the three groups was the amount of social support a mother received from friends and family. For example, the more social support a mother received, the greater the likelihood of her having a male baby.

When social support was statistically equalised across the groups, the stress effects on preterm birth disappeared. "Screening for depression and anxiety are gradually becoming a routine part of a prenatal practice," said Monk. "But while our study was small, the results suggest enhancing social support is potentially an effective target for clinical intervention."

An estimated 30 per cent of pregnant women report psychosocial stress from job strain or related to depression and anxiety, according to the researchers. Such stress has been associated with increased risk of premature birth, which is linked to higher rates of infant mortality and of physical and mental disorders, such as attention-deficit hyperactivity disorder and anxiety, among offspring.