of preeclampsia over the study period. They concluded that the small but consistent elevation in the rate of preeclampsia is a conservative estimate of the true population-level change.
The rate of total cesarean deliveries in the United States increased almost fivefold between 1970 and 1988 and then declined to 20.7 percent in 1996 (Figure 2-20). Since then, the rate increased 50 percent to 31.1 percent—the highest rate ever recorded—in 2006 (Menacker et al., 2006; MacDorman et al., 2008). Primary cesareans (births to women with no previous cesarean delivery) mirror the pattern for total cesareans, while vaginal birth after a previous cesarean (VBAC) increased beginning in the mid-1980s, peaked in 1996, but has declined since that time (MacDorman et al., 2008). An increase in primary cesarean deliveries appears to be the result of changes in obstetric practice rather than in medical risk profiles or maternal request (Menacker et al., 2006; MacDorman et al., 2008). However, a recent meta-analysis concluded that maternal obesity is associated with increased risk of cesarean delivery (Chu et al., 2007). The expanded