Vaginal Birth After Cesarean and Uterine Rupture Rates in California

Vaginal Birth After Cesarean and Uterine Rupture Rates in California for 1995

Short cut to the Numbers / Risk Ratios

Gregory K, Korst L, Cane P, et al. Obstet Gynecol 94:985-9, 1999

Efforts to lower the cesarean section (c-section) rate in the United States have focused mainly on reducing the number of repeat c-sections. The Department of Health and Human Services has targeted a vaginal birth after c-section (VBAC)rate of 35%. The purpose of this study was to describe attempted labor rates,successful VBAC rates, and uterine rupture rates for women with and without prior c-sections. Researchers analyzed California hospital discharge records for 1995. That year there were 536,785 deliveries. Of this group, 66,856 (12.5%) had a history of a prior c-section. 40.3% had elective repeat c-sections, and there were 79 uterine ruptures in this group (0.28%). The remainder (39,096) attempted VBAC. There were 24,024 successful VBACs (61.4%) with 35 ruptures (0.15%) and 15,072 failed VBACs (38.6%) with 174 ruptures (1.15%).

The overall incidence of uterine rupture in the group with prior c-sections was 0.43%. Of the 469,929 women without a prior c-section, 17,209 (3.21%) had an elective primary section with 13 ruptures recorded. There were 51,333 primary sections performed for obstetric indications (9.56%) with 64 ruptures in this group (0.12%). Of the 401,387 women who delivered vaginally (74.78%), 27 ruptures were recorded (0.01%).

***For women with histories of cesarean deliveries, the unadjusted relative risk for uterine rupture was 19.5 compared with women with unscarred uteri.*** When this was adjusted for maternal age, it fell to 16.98. (The significance of this finding was uncertain. Maternal age may be a proxy for other variables, such as the number of previous cesareans.) Looking only at women with histories of c-sections, the unadjusted relative risk of rupture for those attempting VBAC was 1.88. When researchers looked at women who delivered in hospitals with attempted VBAC rates of at least 60%, they found that women were less likely to have c-sections (RR 0.8), more likely to have successful VBACs (RR 1.17) and more likely to have uterine ruptures (RR 1.56%).

Thus, in the largest study reported to date, the uterine rupture rate for all women was found to be 0.07% versus 0.43% for women with prior c-sections. Among women with histories of c-sections, uterine rupture was 1.9 times more likely if a trial of labor was attempted. However, only 34% of uterine ruptures among women with histories of c-sections were attributable to labor. The data did not include neonatal outcome. The authors conclude that risk of uterine rupture is increased among women with prior c-sections and among those attempting VBAC but that the overall rate of rupture is low. Furthermore, increased attempts at VBAC are associated with greater success, suggesting that clinical practices at hospitals with high rates of attempts at VBAC may be different from those in other institutions.

Numbers for Uterine Rupture – spontaneous (no previous CS) post-CS pregnancy
(no labor) and post CS trial of labor / Vaginal Birth After Cesarean (VBAC):

The Big Picture

Total number of births in California for 1995 were 536,785.

Of the original 536,785 birth, 66,856 were post-cesarean pregnancies (12.5%).

Vaginal Birth & Uterine Rupture

There were 51,333 primary sections performed for obstetric indications (9.56 %) with 64 ruptures in this group (0.12 %).

Of the 469,929 women without a prior c-section, 17,209 (3.21 %) had an elective primary section with 13 ruptures recorded.

There were 401,387 (74.78%) vaginal deliveries, a number that includes Pitocin-induced labors, forceps & vacuum extraction. There were 27 spontaneous uterine ruptures recorded or a rate of 0.01 %.

A “spontaneous” ruptures refers to those occurring in uteri that had never been surgically incised. Statistically speaking the majority spontaneous uterine ruptures are the consequence of artificially-stimulated labors -- induced or augmented with the artificial hormones Pitocin, Cytotec and/or prostaglandin.

Post-Cesarean Pregnancies & Uterine Rupture

Of the 66,856 post-cesarean pregnancies (12.5 %). The overall incidence of uterine rupture in the group with prior c-sections was 0.43 %.

Elective Repeat Cesarean & Uterine Rupture

Elective repeat c-sections were done on 40.3% with 79 uterine ruptures (0.28%).

Labor in Post Cesarean Pregnancies & Uterine Rupture

A total of 39,096 women attempted to deliver vaginally (VBAC).

There were 24,024 successful VBACs (61.4 %) with 35 ruptures (0.15 %)

There were 15,072 failed VBACs (38.6 %) with 174 ruptures (1.15 %). This group includes approximately 20 % labors induced or augmented with Pitocin, Cytotec and/or prostaglandins. It also includes “failed” forceps or vacuum extraction that were subsequently followed by Cesarean delivery.

Bottom Line: The Actual Risk for normal labor and VBAC

Uterine rupture ratio (RR) in a normal vaginal birth / intact uteri is 1: 14,866.
Maternal mortality ratio for mothers in this category is 1: 16,666

These facts provide us with compelling reasons to prevent primary cesareans.

RR for successful Vaginal Birth After Cesarean is 1: 1,601
Maternal mortality ratio for mothers in this category is 1: 16,666

RR for elective primary Cesarean is 1:1,323
Maternal Mortality ratio is 1: 5,000

RR in unplanned primary Cesarean is 1: 802
Maternal Mortality ratio is 1: 3,025

RR for elective repeat Cesarean is 1:375
Maternal Mortality ratio is 1: 5,000

Total RR for post Cesarean trial of labor (TOL) is 1:187

RR for unsuccessful post CS labor ending in CS is 1:87
Maternal Mortality ratio is 1: 3,025

Relative to uterine rupture, the safest category is obviously a normal spontaneous vaginal birth. However, the mother with a post-cesarean pregnancy no longer has this option. Under these circumstances, the next safest choice is a spontaneous labor and normal birth with no use of artificial, forcible or mechanical means.

The “added” risk of uterine rupture a post-Cesarean pregnancy in a spontaneous labor and normal birth is 4 ¼ times LESS that that of an elective repeat Cesarean and 133 times less than an induced or augmented post-cesarean labor in which Pitocin, prostaglandins, or Cytotec are used.

The take home message is to decline offers of elective Cesarean surgery and avoid artificially-accelerated or induced labors and operative vaginal birth through physiological management – patience with nature, social and emotional support, upright and mobile mother during labor and right use of gravity for birth.