Nulliparity and duration of pregnancy in multiple gestation.

Objective: We sought to test the hypothesis that nulliparous women with multiple gestations would be more likely to have shorter gestational durations, a higher frequency of previable deliveries, and fewer pregnancy complications when compared with parous women.

Methods: We reviewed the medical records of women who delivered a multiple gestation at 15 or more weeks at 2 institutions between January 1, 1990 and June 30, 2002 (n = 1,035). We recorded demographic data, medical complications, and pregnancy outcomes and analyzed these using paired t tests for continuous variables, chi(2) for categorical variables, and linear regression analysis for the effect of multiple variables on the primary outcome variable, gestational age at delivery.

Results: There was a statistically significant difference in mean gestational age at delivery (34 versus 34.9 weeks, P =.006) between the nulliparous and multiparous groups after excluding women with a history of previous preterm birth and/or midtrimester loss. There were no differences between groups in the likelihood of delivering before 20, 24, or 28 weeks. In linear regression analysis, ongoing fetal number (P <.001), premature rupture of membranes (PROM; P <.001), cerclage (P =.002), and death of 1 or more fetuses (P <.001) were associated with shorter gestation. Cesarean delivery was associated with longer gestation (P <.001). Nulliparous women were significantly more likely to have a pregnancy complicated by hypertension (20.8% versus 9.2%, P <.001), diabetes (7% versus 4%, P =.03), or PROM (24.4% versus 17.3%, P =.006).

Conclusion: Nulliparous women with a multiple gestation deliver their pregnancies, on average, 0.9 weeks earlier than parous women and more frequently experience hypertension, diabetes, and PROM. They are not, however, more likely to deliver before 24 weeks of gestation.