Objective: To determine whether the pattern of prenatal stress, as compared to prenatal stress assessed at a single gestational time point, predicts preterm delivery (PTD).
Design: Perceived stress and anxiety were assessed in 415 pregnant women at 18-20 and 30-32 weeks' gestation.
Main outcome measures: Gestational length was determined by last menstrual period and confirmed by early pregnancy ultrasound. Births were categorized as preterm (< 37 weeks) or term.
Results: At neither assessment did levels of anxiety or perceived stress predict PTD. However, patterns of anxiety and stress were associated with gestational length. Although the majority of women who delivered at term exhibited declines in stress and anxiety, those who delivered preterm exhibited increases. The elevated risk for PTD associated with an increase in stress or anxiety persisted when adjusting statistically for obstetric risk, pregnancy-related anxiety, ethnicity, parity, and prenatal life events.
Conclusions: These data suggest that the pattern of prenatal stress is an important predictor of PTD. More generally, the findings support the possibility that a decline in stress responses during pregnancy may help to protect mother and fetus from adverse influences associated with PTD.