Vaginal Birth After Cesarean Birth --- California, 1996--2000

In 2000, of all births in the United States, 23% were cesarean (1), approximately 37% of which were repeat cesarean births (i.e., births to women who had a previous cesarean birth). Approximately 60% of cesarean births might be by elective repeat cesarean delivery (ERCD) (2). Because cesarean birth is associated with higher maternal morbidity than routine vaginal birth (2,3), two of the national health objectives for 2010 are to reduce the cesarean birth rate among women at low risk to 15% of women who are giving birth for the first time (objective no. 16-9a) and to 63% of women with previous cesarean births (objective no. 16-9b) (4). A key strategy to reduce the repeat cesarean birth rate is to promote vaginal birth after cesarean (VBAC) as an alternative to ERCD. Achieving the national health objective for 2010 will require increasing the VBAC rate to 37% (1,3,4). During 1989--1999, VBAC rates in the United States increased from 19% in 1989 to 28% in 1996 and then decreased to 23% in 1999 (1). This report summarizes an analysis of California's VBAC rates during 1996--2000, which indicates that the VBAC rate in California decreased by 35%, from 23% in 1996 to 15% in 2000. Strategies to improve VBAC rates might include educating women about the risks for complications and benefits of VBAC, ensuring careful selection of VBAC candidates, developing guidelines for management of labor, and educating health-care providers about reducing VBAC risks.

To assess California's progress toward meeting the national health objectives for 2010, CDC analyzed birth certificate data from the California Office of Vital Statistics. The analysis included all births to California residents during 1996--2000 for which the mother had a previous cesarean birth (i.e., the delivery method as recorded on the birth certificate was either a repeat cesarean birth or VBAC). Birth certificate files with unknown delivery methods were excluded. A birth was defined as VBAC if the delivery method was recorded either as VBAC or as VBAC and another type of vaginal birth (e.g., forceps- or vacuum-assisted delivery). The VBAC rate for each year during 1996--2000 was determined by dividing the number of women having VBAC per year by the number of women with previous cesarean birth giving birth that year, and trends were tested for statistical significance using Chi-square for linear trend. Maternal race/ethnicity, age, education, and insurance type were stratified, and VBAC rates were calculated for each population. VBAC rates for each population during 1996--2000 were compared to determine the relative percentage change and 95% confidence intervals.

During 1996--2000, the VBAC rate in California decreased from 23% (12,767 of 55,985 women with previous cesarean births) in 1996 to 15% (8,562 of 58,005) in 2000, a decline of 35% (Figure). After maternal race/ethnicity, age, insurance status, and education were stratified, a consistent downward trend in VBAC rates was observed for all populations (Table). By race/ethnicity, Asian/Pacific Islander women had the highest VBAC rates, ranging from 25% in 1996 to 18% in 2000; VBAC rates among American Indian/Alaska Native women declined the most, and rates among non-Hispanic black women declined the least. By age, the highest VBAC rates occurred in 1996 among women aged <19 years and in 2000 among women aged 20--29 years, and the lowest rates occurred among women aged >40 years in all years; VBAC rates declined the most (49%) among women aged <19 years. By education level, college graduates had the highest VBAC rates, and women with less than a high school education had the lowest rates; declines in VBAC rates were similar among women of all education levels. By insurance coverage, women with Health Maintenance Organization (HMO) coverage had the highest VBAC rates, and women with MediCal/Medicaid had the lowest rates; the decline in VBAC rates was significantly smaller among women with HMO insurance than among women with MediCal/Medicaid or private (i.e., fee-for-service) insurance.

Reported by: GF Chavez, MD, E Takahashi, PhD, Maternal Child Health Br, California Dept of Health Svcs; K Gregory, MD, Cedars-Sinai Medical Center, Los Angeles, California. S Durousseau, MD, EIS Officer, CDC.

Editorial Note:

The findings in this report highlight changes in obstetric practice during 1996--2000 across all populations of women in California toward more repeat cesarean births and fewer VBACs. The decreasing trends in VBAC rates described in this report indicate that California probably will not meet the national health objective for VBAC rates in 2010. The decreasing trend in California VBACs is similar to national data demonstrating a decline in VBAC rates across all racial/ethnic and age populations during 1996--2000 (1). The decrease in VBAC rates might reflect medical and legal pressures, provider preferences, changed standards of obstetric practice, concerns about convenience, fear of prolonged or failed labor, and maternal preferences (3,5).

Before the 1980s, obstetricians performed ERCD for women with a previous cesarean birth routinely because of the risk for uterine rupture among women in labor who had uterine scars, a complication associated with high perinatal and maternal mortality (2,3,5,6). In 1980, the National Institutes of Health concluded that a trial of labor after cesarean (TOLAC) birth was safe for women with previous cesarean births with low transverse uterine scars (7). Studies conducted in the early 1990s indicated that VBAC and TOLAC were not associated with increased maternal and perinatal mortality and morbidity compared with ERCD and that 60%--80% of women with TOLAC will deliver vaginally successfully (3,6,8). In 1999, the American College of Obstetricians and Gynecologists issued guidelines specifying that the majority of women with low-transverse incisions with no contraindication to vaginal birth are candidates for TOLAC (3).

Data are conflicting about the use of TOLAC, and this conflict might be contributing to the declining VBAC rates in California. Some data have suggested an association between TOLAC and uterine rupture (1). A recent U.S. study of 20,000 women with previous cesarean births found that women who had TOLAC, especially women who had labor induced by prostaglandins, were more likely to have uterine rupture than those women with ERCD and no labor (9). Women with unsuccessful TOLAC resulting in nonelective cesarean births have more fevers, infections, and prolonged hospitalizations than women delivering by VBAC or by ERCD (3,6). Conversely, compared with women delivering successfully by VBAC, women delivering by ERCD have more infections, hemorrhages, problems with subsequent pregnancies, and potentially decreased infant bonding (3,5,6). In addition, the choice of birthing method is influenced by a mother's values and beliefs (3,5).

The findings in this report are subject to at least three limitations. First, because birth certificates do not record information on provider or maternal preferences, it was not possible to identify the reasons for the decline in the VBAC rate. Second, because birth certificate data do not record how many women have TOLAC, it was not possible to assess whether fewer women are offered, accept, or attempt TOLAC or to calculate the VBAC success rate. Finally, because birth certificates might not record delivery methods correctly (e.g., VBAC classified as another type of vaginal birth or a primary cesarean birth classified as a repeat cesarean birth) (10), VBAC rates might be underestimated. Despite these limitations, conclusions about trends in VBAC rates can be made because the methodology used to collect and record information on birth certificates remained unchanged during 1989--2000 (2).

The reasons for the decreasing trend in VBAC rates are unclear, and potential research priorities might include determining the maternal, provider, and institutional factors affecting VBAC rates. The changing trends noted in this report highlight the complexity of birth-related medical, socioeconomic, and cultural issues and indicate a need for increased understanding of these issues.

VBAC rates might be improved by ensuring careful selection of VBAC candidates (i.e., women with one previous low-transverse cesarean incision delivering full-term singletons in vertex presentation), developing guidelines to manage labor, and educating health-care providers about reducing the risks for complications from VBAC (3,5). Surveillance of VBAC rates should continue at both institutional and population levels. Women should be informed about the risks for complications and benefits of VBAC and cesarean birth so they can make informed birth choices; the decision to attempt VBAC should be based on the clinical status of the pregnancy and on discussions between the woman and her health-care provider.

References

1. Martin JA, Hamilton BE, Ventura SJ, Menacker F, Park MM. Births: final data for 2000. National and vital statistics reports. Hyattsville, Maryland: National Center for Health Statistics, 2002. Available at http://www.cdc.gov/nchs/data/nvsr/nvsr50/nvsr50_05.pdf.
2. Gregory K, Curtin S, Taffel S, Notzon F. Changes in indications for cesarean delivery: United States, 1985 to 1994. Am J Public Health 1998;88:1384--87.
3. American College of Obstetricians and Gynecologists. Evaluation of cesarean delivery. Washington, DC: American College of Obstetricians and Gynecologists, 2000.
4. U.S. Department of Health and Human Services. Healthy people 2010, 2nd ed. With understanding and improving health and objectives for improving health (2 vols). Washington, DC: U.S. Department of Health and Human Services, 2000.
5. Sachs B. Vaginal birth after cesarean: a health policy perspective. Clin Obstet Gynecol 2001;44:553--60.
6. McMahon M. Vaginal birth after cesarean. Clin Obstet Gynecol 1998; 41:369--81
7. National Institutes of Health. Cesarean childbirth. Washington, DC: National Institutes of Health, 1981. (NIH publication no. 82-2067).
8. Gregory KD, Korst LM, Cane PC, Platt LD, Katherine K. Vaginal birth after cesarean and uterine rupture rates in California. Obstet Gynecol 1999;94:985--9.
9. Lydon-Rochelle M, Holt VL, Easterling TR, Martin DP. Risk of uterine rupture during labor among women with a prior cesarean delivery. N Engl J Med 2001;345:3--8.
10. Green DC, Moore JM, Adams MM, Berg CJ, Wilcox LS, McCarthy BJ. Are we underestimating vaginal birth after previous cesarean birth? The validity of delivery methods from birth certificates. Am J Epidemiol 1998;147:581--5.

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