Rates of cesarean delivery are rising globally. They now account for more than 30% of births in the United States. As a result, more women than ever face the decision of whether they should attempt a vaginal delivery after having undergone a cesarean (VBAC) or choose an elective repeat cesarean (ERCS).
The results of a new study could help them make a more informed choice. Researchers in the United Kingdom have found that women who undergo a VBAC have more than twice the chance of developing serious pelvic floor dysfunction as those who opt for a second cesarean.
“We feel these findings provide important additional information to be able to counsel this growing group of women who’ve had a cesarean section in the past about the risks and benefits associated with their future birth choices,” said lead author Kate Fitzpatrick, DPhil, of the National Perinatal Epidemiology Unit at the University of Oxford.
Current guidelines suggest that women be offered the option of a VBAC if they have no contraindications to a vaginal birth following counseling about risks and benefits of each choice. By delivering vaginally, women avoid potential complications of surgery, such as infection and blood loss; spend less time in the hospital; and have more success with breastfeeding.
But VBAC is not risk free either: Infection and blood loss also occur, and, in rare cases, the scar from the previous cesarean delivery can rupture. This can cause life-threatening uterine bleeding and fetal distress. Little is known about the long-term trade-offs.
In a study published in PLOS Medicine today, researchers in the United Kingdom address this gap. Researchers from the University of Oxford and the University of Aberdeen identified a cohort of singleton term births among women who had undergone one or more cesarean deliveries between 1983 and 1996. Using Scottish national datasets, they determined whether women were planning to attempt VBAC or undergo ERCS and tracked the outcomes for over 20 years.
Of the 47,414 women, 1159 (2.44%) required some type of pelvic floor surgery during the study period. The crude incidence of these procedures among women in the VBAC group was 1.75 per 1000 deliveries, compared to 0.66 per 1000 among those in the ERCS group.
After adjusting for demographics and maternal medical and obstetric–related factors, the risk of undergoing any type of pelvic floor surgery was more than twice as high among women who had planned for a VBAC than among those who had chosen ERCS.
Among those requiring surgery, the most common diagnoses were pelvic organ prolapse (53%) and urinary incontinence (46%), with adjusted hazard ratios of 3.17 (95% CI, 2.47 – 4.09) and 2.26 (95% CI, 1.79 – 2.84), respectively.
Kate Fitzpatrick, DPhil, of the National Perinatal Epidemiology Unit at the University of Oxford, who led the study, said the research helps define the magnitude of a long-term outcome of VBAC.
“The current guidelines and the counseling focuses on the more short-term complications, such as risk of uterine rupture,” Fitzpatrick told Medscape Medical News.
Fitzpatrick also highlighted another finding: Among women who had planned a VBAC but ultimately required an in-labor nonelective repeat cesarean, the risk of undergoing pelvic surgery was similar to that among women who had planned an ERCS.
That fact intrigued Annetta Madsen, MD, a urogynecologist in the Department of Obstetrics and Gynecology at Mayo Clinic in Rochester, Minnesota.
Few studies have distinguished the effects of labor — such as the engagement of the fetal head into the pelvis for long periods — from the effect of the vaginal delivery itself. The UK findings suggest that passage through the birth canal carries less of a risk of pelvic floor injury than does vaginal delivery.
Should the study findings change the way obstetric care providers discuss risks and benefits of VBAC with their patients?
“It may seem like the easy answer is that everyone should just have a cesarean section to avoid pelvic floor injury with childbirth, but that comes with risks as well,” Madsen said. “There’s always a balancing act between the risk of potential injury to pelvic floor linked to vaginal delivery weighted against the surgical risks associated with cesarean section.”
Fitzpatrick was funded by a National Institute for Health and Care Research Doctoral Research Fellowship for this research project. The funders had no role in study design, data collection, data analysis, decision to publish, or preparation of the manuscript.
PLoS Med. Published online November 22, 2022.
Ann Thomas, MD, MPH, is a pediatrician and epidemiologist living in Portland, Oregon.