Neonatal Mortality Risk for Repeat Cesarean Compared to Vaginal Birth after Cesarean (VBAC) Deliveries in the United States, 1998–2002 Birth Cohorts

Fay Menacker; Marian F. MacDorman; Eugene Declercq

Disclosures

Matern Child Health J. 2010;14(2):147-154. 

In This Article

Results

Trends in the repeat cesarean rate were similar for all women, low-risk women (women with full-term, singleton, vertex infants), and NIR women (Fig. 1). There were virtually no differences in the trends across all three groups with all having nearly a 90% repeat cesarean rate in 2002. There was an overall increase in the repeat cesarean rate for all groups of 11–13% between 1991 and 2002. For all three groups the rates declined by 9–11% between 1991 and 1996, and then rose by 22–26% between 1996 and 2002. In 2002 there were 158,586 "no indicated risk" repeat cesareans in the U.S., an increase of 61,454, compared with 1996. Repeat cesareans to women at "no indicated risk" represented over half (53%) of the total increase (116, 025) in repeat cesareans in the U.S. during that period. The proportion of NIR mothers who had a previous cesarean decreased from 38.8% in 1991 to 34.5% in 1996, (data not shown) then increased to 38.8% by 2002 (data not shown).

Figure 1.

Repeat cesarean rates (per 100 births to women who had a previous caesarean) for all women, low-risk women (per 100 women with singleton, full term (37+ weeks) infants in vertex presentation), and women at no indicated risk (NIR) [per 100 women with singleton, term (37–41 week) infants in vertex presentation and no reported medical risk factors or complications of labor and/or delivery reported on the birth certificate]: United States, 1991–2002

In Table 1 we present descriptive information on the characteristics of all women, low-risk women and the 158,586 women at no indicated risk and their corresponding repeat cesarean rate in 2002, by maternal race, age, parity, initiation of prenatal care, education, smoking status and marital status and by infant gestational age and birthweight. With few exceptions (American Indian/Alaskan Native ethnicity, no prenatal care, 40–41 weeks gestation) for almost every variable examined, NIR women had rates of repeat cesarean delivery around 90%, and their rates were slightly but significantly higher than rates for all women and low-risk women. Repeat cesarean rates were highest for NIR women who were parity 2 (91.9%) and gave birth at 37–39 weeks (91.1%). They were lowest for those who had no prenatal care (75.8).

Repeat cesarean rates for NIR women varied among states and by region (Fig. 2), but tended to be higher in the South and Southeast (90.0–93.9%) and lower in the West and upper Midwest (74.0–89.9%). Vermont (74.2) and North Dakota (79.9) had the lowest rates; rates were highest in Louisiana (93.9) and Mississippi (93.7). For many years, researchers have documented significant regional variation in rates and costs of surgical procedures not explained by patient characteristics.[11,12]

Figure 2.

Repeat cesarean rates for women at no indicated risk (NIR) [women with singleton, term (37–41 weeks of gestation) births in vertex presentation with no medical risk factors or complications of labor and or/delivery reported on the birth certificate]: United States, 2002

Table 2 presents neonatal mortality rates for births by VBAC and by repeat cesarean to low-risk and NIR women, for the 1998–2002 birth cohort. For low-risk women the neonatal mortality rate was 1.03 neonatal deaths per 1,000 live births, while for the subset of the low-risk group, NIR women, it was 0.76 per 1,000. Not surprisingly for such low-risk groups, numbers and rates of infant and neonatal mortality were very low, compared with the neonatal mortality rate of 4.76 for all births in the US for this time period. Notable differentials in mortality by method of delivery existed with a neonatal mortality rate 20% higher for infants delivered by repeat cesarean compared to infants in VBAC deliveries in the NIR group and 29% higher in the low-risk group. As expected, differences by method of delivery were largest for early neonatal deaths (<7 days), since one would expect a greater effect of method of delivery on mortality close to the time of delivery.

There was little variation across different demographic groupings in repeat cesarean rates. Nonetheless, logistic regression was used to assess the adjusted risk of neonatal mortality for VBAC and repeat cesarean deliveries for low-risk women (Model 1) and for NIR women (Model 2) (Table 3). In both models the dependent variable is total neonatal mortality. After controlling for demographic and medical covariates (which influence neonatal mortality and were available on the birth certificate), the adjusted odds ratio for neonatal mortality associated with repeat cesarean delivery for low-risk women is 1.36 (95% confidence interval = 1.20–1.55) compared to VBAC. After controlling for the same covariates as in Model 1, the adjusted odds ratio for repeat cesarean delivery for NIR women Model 2) was 1.24 (0.99–1.55) (not significantly different).

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