Effect of maternal stress during pregnancy on the risk for preterm birth

Background: Preterm birth defined as birth prior to 37 weeks of gestation is caused by different risk factors and implies an increased risk for disease and early death for the child. The aim of the study was to investigate the effect of maternal stress during pregnancy on the risk of preterm birth. Methods: A case-control study that included 340 women; 168 women who gave birth preterm and 172 women who gave birth at term. Data were manually extracted from standardized medical records. If the medical record contained a psychiatric diagnosis or a self-reported stressor e.g., depression or anxiety the woman was considered to have been exposed to stress during pregnancy. Adjusted odds ratio (AOR) was used to calculate the attributable risk (AR) of maternal stress during pregnancy on preterm birth, both for the women exposed to stress during pregnancy (AR1 = (AOR-1)/AOR) and for the whole study population (AR2 = AR1*case fraction). Results: Maternal stress during pregnancy was more common among women who gave birth preterm compared to women who gave birth at term (p <0.000, AOR 2.15 (CI = 1.18-3.92)). Among the women who experienced stress during pregnancy 54 % gave birth preterm with stress as an attributable risk factor. Among all of the women the percentage was 23 %. Conclusions: Stress seems to increase the risk of preterm birth. It is of great importance to identify and possibly alleviate the exposure to stress during pregnancy and by doing so try to decrease the preterm birth rate.