The Risk of Perinatal Mortality in Nulliparous Women Compared to Primiparous Women at Term.

Objective: The aim of this study was to determine the rate of perinatal mortality among nulliparous women compared with primiparous women at term and further characterize the risk of stillbirth by each week of gestation.

Study Design: This is a retrospective cohort study of all term, singleton, nonanomalous births comparing perinatal mortality (stillbirth and neonatal death [NND]) between primiparous (parity = 1, with no history of abortion) and nulliparous (parity = 0) women who delivered in California between 2007 and 2011. Chi-squared tests and multivariable logistic regression analyses were performed to determine the frequencies and strength of association of perinatal mortality with parity, adjusting for maternal age, race, body mass index, pregestational diabetes, chronic hypertension, fetal sex, smoking status, and socioeconomic status.