Pregnancy-specific stress, prenatal health behaviors, and birth outcomes.

OBJECTIVE Stress in pregnancy predicts earlier birth and lower birth weight. The authors investigated whether pregnancy-specific stress contributes uniquely to birth outcomes compared with general stress, and whether prenatal health behaviors explain this association. DESIGN Three structured prenatal interviews (N = 279) assessing state anxiety, perceived stress, life events, pregnancy-specific stress, and health behaviors. MAIN OUTCOME MEASURES Gestational age at delivery, birth weight, preterm delivery (<37 weeks), and low birth weight (<2,500 g). RESULTS A latent pregnancy-specific stress factor predicted birth outcomes better than latent factors representing state anxiety, perceived stress, or life event stress, and than a latent factor constructed from all stress measures. Controlling for obstetric risk, pregnancy-specific stress was associated with smoking, caffeine consumption, and unhealthy eating, and inversely associated with healthy eating, vitamin use, exercise, and gestational age at delivery. Cigarette smoking predicted lower birth weight. Clinically-defined birth outcomes were predicted by cigarette smoking and pregnancy-specific stress. CONCLUSION Pregnancy-specific stress contributed directly to preterm delivery and indirectly to low birth weight through its association with smoking. Pregnancy-specific stress may be a more powerful contributor to birth outcomes than general stress.