Extreme parity and the risk of stillbirth

We examined the relationship between extreme parity and risk for stillbirth in the United States.

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 I), 5-9 (high parity, category II), 10-14 (very high parity, category III), and 15 or more (extremely high parity, category IV) prior live births were computed using logistic regression.

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 I, category II, category III, 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 [OR] 1.05, 95% confidence interval [CI] 1.02-1.07), category III (OR 1.97, 95% CI 1.81-2.15), and category IV (OR 2.31, 95% CI 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% CI 1.29-5.74), 16 (OR 3.14, 95% CI 1.17-8.41), 17 (OR 6.11, 95% CI 2.56-16.5), and 18 or more prior live births (OR 16.17, 95% CI 8.77-29.82) (P for trend < .001).

The risk for stillbirth is substantially elevated among very high and extremely high parity women, and care providers may consider these groups for targeted periconceptional counseling.

II-2.