Extreme parity and the risk of stillbirth

Objective: We examined the relationship between extreme parity and risk for stillbirth in the United States. Methods: Singleton deliveries at 20 weeks of gestation or later in the United States from 1989 through 2000 were analyzed. Risk for stillbirth in women with 1-4 (moderate parity, category 1), 5-9 thigh parity, category 11), 10-14 (very high parity, category 111), and 15 or more (extremely high parity, category IV) prior live births were computed using logistic regression. Results: Overall, 27,069,385 births, including 1,206 to extremely high parity mothers, were analyzed. Of the 81,386 stillbirths, 71,623 (2.8/1,000), 9,206 (5.0/1,000), 531 (14.4/1,000), and 26 (21.6/1,000) cases occurred among category 1, category 11, category 111, and category IV gravidas, respectively. With category I as referent category, the odds ratio for stillbirth increased consistently with ascending parity after adjusting for potential confounders: category II (odds ratio vertical bar OR vertical bar 1.05, 95% confidence interval vertical bar Cl vertical bar 1.02-1.07), category III (OR 1.97, 951% Cl 1.81-2.15), and category IV (OR 2.31, 950% Cl 1.56-3.42) (P for trend < .001). Among extremely high parity women (category IV), the odds ratio for stillbirth also increased with unit increment in the number of prior live births: 15 (OR 2.72, 95% Cl 1.29-5.74), 16 (OR 3.14, 95(/o Cl 1.17-8.41), 17 (OR 6.11, 95% Cl 2.56-16.5), and 18 or more prior live births (OR 16.17, 95% C1 8.77-29.82) Wfor trend < .001). Conclusions: The risk for stillbirth is substantially elevated among very high and extremely high parity women, and care providers may consider these groups for targeted pericanceptional counseling.