Objective To explore trends in primary cesarean delivery rates among parous women with singleton pregnancies in the United States between 1990 and 2003. Methods The analysis used data from national birth files based on U.S. birth certificates between 1990 and 2003. The primary cesarean delivery rate was defined as the number of primary cesarean deliveries per 100 deliveries among parous women with singleton pregnancies who have not had a previous cesarean delivery. A stratified analysis was employed to investigate whether trends varied by maternal age, gestational age, race/ethnicity and region. Results In the United States, the primary cesarean delivery rate among parous women decreased modestly from 7.1% in 1990 to 6.6% in 1996 but increased progressively to 9.3% in 2003. The increase in cesarean rates from 1996 to 2003 varied substantially by race/ethnicity: Hispanic and non-Hispanic white women exhibited lower and similar rates, while rates for non-Hispanic black women were consistently higher and rose by a far greater extent across the years. There were substantial differences in cesarean delivery trends across geographic divisions, with greatest increases observed in the Mid-Atlantic, South Central and South Atlantic areas of the United States. Primary cesarean rates also declined considerably with increasing gestational age. Conclusion Similar to the overall cesarean delivery rate, primary cesarean rates among parous women with singleton pregnancies increased substantially in the United States since 1996.

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