TABLE 3.
Odds Ratios for Preterm Obstetrical Intervention (Cesarean Delivery or Induction of Labor): United States, 1991, 1996, 2001, and 2006
| Year of Birth | Model 1,a OR (95% CI) | Model 2,b OR (95% CI) | Model 3,c OR (95% CI) |
| 2006 | 1.84* (1.82, 1.85) | 1.97* (1.96, 1.99) | 1.88* (1.87, 1.90) |
| 2001 | 1.45* (1.43, 1.46) | 1.52* (1.51, 1.54) | 1.48* (1.47, 1.49) |
| 1996 | 1.14* (1.13, 1.15) | 1.18* (1.17, 1.19) | 1.15* (1.14, 1.16) |
| 1991 (Ref) | 1.00 | 1.00 | 1.00 |
Note. OR = odds ratio; CI = confidence interval. Data were derived from the natality detail files of the National Center for Health Statistics.
a
Unadjusted.
b
Adjusted for year of birth, maternal age, maternal race/ethnicity, total birth order, very preterm status, and moderately preterm status.
c
Adjusted for all of the variables included in model 2 along with diabetes, chronic hypertension, and pregnancy-associated hypertension.
*P < .001.