Pregnant women with both high stress levels and high blood pressure may be at increased risk of having an underweight baby.

Researchers in America assessed the stress levels of 170 women, white and African-American at different points during pregnancy. One questionnaire asked about chronic stressors in everyday life, such as whether or not the women worried about paying their bills or about crime in their neighbourhood. They were also asked whether they often felt stressed or out of control, and about any symptoms of general anxiety and pregnancy-related anxiety.

It was found that women with both high stress levels and high diastolic blood pressure were at increased risk of having an underweight baby. While the high stress/high blood pressure combination seemed to affect birth weight for white and black women alike, black women were more likely to have both problems. This higher prevalence may help explain why African-American women are generally at greater risk of having a low-birth-weight infant.

The findings suggest stress and high blood pressure may affect fetal growth in a number of ways by constricting blood flow to the uterus, for example, or through effects on hormone levels or immune system function. Thus, pregnant women with both high blood pressure and chronic stress should be monitored more closely.