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November 19, 2001
News this month Each year in the U.S. about 60 percent of women who have experienced previous cesarean deliveries attempt to deliver subsequent babies vaginally. For the last few years there has been increasing concern that vaginal births after C-section (known as VBAC) increase the risk of uterine tears among these women. Earlier this year, a study published in The New England Journal of Medicine substantiated these concerns, particularly when labor is induced by giving women prostaglandin hormones. Prostaglandins increase risk significantly Lead researcher Mona Lydon-Rochelle, PhD, found the risk of uterine rupture was more than three times higher for those who went into spontaneous labor than those who had a planned, repeat C-section. Women induced with prostaglandins were 15 times more likely to experience uterine rupture.
Among women who had to be induced, the risk was even greater. Women induced with prostaglandins were 15 times more likely to experience uterine rupture and those induced with a nonprostaglandin agent (either the synthetic hormone, oxytocin, or by mechanically manipulating the uterus) were almost five times more likely to experience a rupture compared with women who had a repeat C-section. The odds of a uterine rupture among the women in this study were:
Uterine rupture is a rare but potentially fatal complication, which puts the baby's life at risk and can cause serious injury to the woman. Rupture can lead to the need for blood transfusions and hysterectomy. Although the overall death rate from rupture was quite low in the NEJM study, those women who had uterine ruptures were far more likely to have serious complications or to lose the baby. The researchers found the infant death rate was 10 times higher among those who had ruptures. In an accompanying editorial, Michael F. Greene, MD, director of maternal-fetal medicine at Boston's Massachusetts General Hospital, wrote the results are perfectly consistent with previous studies, with one exception. “What's new and different about this study is…the estimate of risk of uterine rupture associated with prostaglandin induction of labor.” Women who attempt labor [after a previous C-section] should make sure the hospital and staff they intend to use are equipped to manage any complications that might occur.
Take special precautions with VBACs 
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VBAC decision based on individual risk For decades, the standard of practice for obstetricians was, "Once a cesarean, always a cesarean." That axiom was based on concern about how well the scar on the uterus that results from a cesarean would withstand labor. The tide turned in the early 1980s based on several large studies and shifts in both popular opinion and medical practice. Women began to be encouraged to deliver vaginally. In fact, from 1989 to 1996, the rate of vaginal births after cesarean (VBACs) in the U.S. increased by 50 percent. “From 1989 to 1996, the rate of vaginal births after cesarean in the U.S. increased by 50%.”
Almost all patients who had had a previous cesarean were encouraged to attempt a VBAC. In addition, induction of labor and the use of cervical ripening agents were also considered safe. But over the last two years, obstetricians have begun to question the broad-based commitment to VBACs, especially when it's necessary to ripen (soften) the cervix before inducing labor. Why postaglandins are used A class of compounds, called prostaglandins, have proven to be helpful in ripening the cervix so vaginal delivery is possible. The prostaglandins work by causing repetitive and, at times, strong uterine contractions, thus softening, thinning and dilating the cervix. “One particular prostaglandin, called misoprostol, is associated with most of the problems.”
In general, a normal, unscarred uterus can handle the stimulation of the prostaglandins without significant risk. However, recent reviews of patients with previous C-section scars suggest there is a higher risk of uterine rupture than previously recognized. One particular prostaglandin, called misoprostol, is associated with most of the problems. In fact, the American College of Obstetricians and Gynecologists has recommended against its use in patients who have had a previous C-section. The recent articles in the NEJM support that recommendation and suggest all prostaglandins when used for cervical ripening are associated with an increased risk of uterine tearing. Patient selection is key Proper patient selection is key to safe vaginal deliveries. Physicians need to consider their patients' personal preference, general health and the reason for the first C-section. The type of uterine scar is also critical. Women with vertical scars are not considered safe candidates for a vaginal birth. Patients with a small pelvis, those who are carrying large babies and/or babies with a floating vertex (babies whose heads are not engaged in the birth position) and those with a very unfavorable cervix after their due date are not likely to be good candidates for a VBAC. “Properly selected patients…especially those who go into labor spontaneously, are likely to progress to a safe vaginal delivery.”
Properly selected patients, however, especially those who go into labor spontaneously, are likely to progress to a safe vaginal delivery and avoid the risks associated with major surgical procedures such as C-sections. Careful selection is key. Not all patients should attempt VBAC, but
many may be considered safe candidates. If the progress of labor slows
or stops, however, physicians need to re-evaluate the situation and
determine if an operative delivery is best. Dr. Lynch is an attending gynecologist/obstetrician at Yale-New Haven Hospital and a clinical professor in obstetrics and gynecology at the Yale School of Medicine. He is a partner of the Greater New Haven Obstetrics/Gynecology Group with offices in New Haven, Orange and Hamden. |
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The Yale-New Haven Experience For some years, Yale-New Haven has engaged in a program to reduce the number of C-sections. This issue of HealthLINK illustrates the benefit of such an approach because women who have delivered by C-section face more complicated choices in subsequent deliveries. If a woman is an appropriate candidate for vaginal birth after C-section (VBAC), we encourage her to consider VBAC. The Obstetrical Practice Council at Yale-New Haven closely monitors the rate of uterine rupture and separation of the original uterine scar. The YNHH rate is extremely low and, for at least a year, there have been no negative outcomes. While vaginal birth after cesarean (VBAC) has risks and benefits, there are also risks and benefits to having a Cesarean. You should discuss both with your health care provider. |
