Infants' low birth weight is linked to low-income mothers' chronic stress.

Low-income women who suffer from chronic psychosocial stress are at increased risk of having a low-birth-weight baby, according to findings from a study of Illinois welfare recipients. (1) Overall, 13% of women who gave birth during the course of the study delivered a low-birth-weight infant, but the proportion was significantly elevated among those who reported a variety of stressors. For example, it was 31% among those who had difficulty affording food for their household and 34% among those who had poor skills for coping with external stressors. Multivariate analyses confirmed that these and other stressors were independently associated with the likelihood of having a low-birth-weight baby.

The sample was derived from a cohort of women participating in a longitudinal study of the maternal and child health effects of making the transition from welfare to work. Members of the larger cohort had been randomly selected from among families in nine counties who received Temporary Assistance for Needy Families in 1998; participants were interviewed annually from 1999 to 2004. To examine associations between psychosocial stress and low birth weight (defined as less than 2,500 g), researchers identified women in the cohort who had singleton births during the first four years of the study and analyzed data collected within six months of delivery.

Of the 294 women who made up the analytic sample, 77% were black, 16% were white, 5% were Hispanic and the rest were members of other racial or ethnic groups. The women ranged in age from 19 to 47; two-thirds were 26 or younger. Among women who reported their household income, the mean income was $13,416. Thirteen percent of women had low-birth-weight infants; these women were significantly older than others (28 vs. 25 years, on average), but the groups did not differ with respect to any other demographic characteristics examined (race or ethnicity, education, parity, marital status and recent gap in health insurance).

In univariate analyses, the proportion of women whose infants were low-birth-weight was significantly related to five of 16 psychosocial stressors studied. It was 17% among unemployed women, 23% among those living in crowded housing, 27% among those who had a child with a chronic illness, 31% among those who had difficulty paying for the household's food and 34% among those with poor coping skills. Among women not reporting these stressors, by contrast, only 6-12% had low-birth-weight babies.

Except for home crowdedness, each of these stressors remained significantly associated with a woman's likelihood of having a low-birth-weight baby in analyses controlling for maternal age. Odds ratios ranged from 2.6 (for food insecurity) to 4.0 (for poor coping skills).

The researchers note that the finding of a positive relationship between maternal age and the frequency of low birth weight contradicts earlier findings for the general population. By way of explanation, they suggest that maternal age is a "proxy" for chronic stressors that are difficult to measure and that the relationship is evidence of the "cumulative adverse effects of chronic psychosocial stress" among low-income women. A better understanding of the association between chronic stress and low birth weight, they conclude, "may allow the development of more effective risk assessment measures or even interventions that could mitigate the damaging effects of the stress response" in low-income women.

REFERENCE

(1.) Borders AEB et al., Chronic stress and low birth weight neonates in a low-income population of women, Obstetrics & Gynecology, 2007, 109(2, part 1):331-338.