One Third of First-Time Pregnancies Delivered by Cesarean

From Medscape Medical News
Fran Lowry

August 30, 2010 — The rate of cesarean deliveries in the United States is continuing its upward trajectory, according to a new study released today. Now accounting for 30% of all deliveries, the rate of cesarean delivery has increased 50% from 1996 to 2007 and shows no signs of diminishing.

Results of a large, retrospective, observational study conducted by the National Institute of Child Health and Human Development and National Institutes of Health, in collaboration with 12 institutions across the United States, show that:

•1 in 3 women pregnant for the first time are now being delivered by cesarean.
•Repeat cesarean after a previous caesarean delivery now accounts for one third of all cesarean deliveries.
•The rate of trial of labor after a previous cesarean is low, at 29%, and the success rate for a trial of labor has declined to 57%.
•44% of women attempting vaginal delivery had their labor induced, and their rate of cesarean delivery is twice as high as women who have spontaneous labor.
•Half of cesarean deliveries were conducted before 6 cm of cervical dilation — which is considered an early phase of labor, especially in first-time mothers — induced labor, or women who are attempting vaginal birth after cesarean delivery (VBAC).

The results were announced by lead researcher Jun Zhang, PhD, MD, from the Eunice Kennedy Shriver National Institute of Child Health & Human Development. The findings are published in the September issue of the American Journal of Obstetrics and Gynecology.

Speaking at a teleconference today, Dr. Zhang told reporters he was particularly surprised by the finding that 1 of every 3 first-time mothers are delivering via cesarean.

"This has important consequences for future pregnancies, since vaginal delivery after C-section is still thought to be somewhat risky, despite recommendations by the American College of Obstetrics and Gynecology (ACOG) to the contrary," he said.

Another surprising finding was that many cesarean deliveries are being done very early in labor, before 6 cm of dilation, Dr. Zhang added.

The study, called the Consortium on Safe Labor, was conducted to collect comprehensive information on current labor and delivery practice across the United States. It included 12 clinical centers, made up of a total of 19 hospitals, located across 9 ACOG districts. Most were university or community teaching hospitals, and only 2 were nonteaching community hospitals. They were chosen because electronic medical records were available at each institution and because they were geographically representative of all ACOG districts in the United States.

Dr. Zhang told Medscape Medical News that several factors may be driving the increase in cesarean deliveries.

"Delayed child bearing, increased maternal body mass, more twin pregnancies, and low use of vaginal birth after previous C-section, which is increasing because of 2 forces — the increasing C-section rate in first-time mothers and the decrease in VBACs. Put all these together, and it looks as if the upward trajectory may continue for a little while."

He admitted that the study has limitations. The participants are not a random sample of what is going on in the United States, and academic institutions are overrepresented in the study sample, he told Medscape Medical News.

"Although this is quite a comprehensive database, it is not totally representative of the United States population. That is one drawback."

The second is that the study is retrospective.

"We think that the quality of information we have is very good, but we still have to rely on what is recorded in the medical records. We extracted the information from the hospital database, so our data are only as good as the medical record. That is another deficiency."

Dr. Zhang said that reducing this high rate of cesarean delivery will need to focus on preventing unnecessary primary cesarean deliveries "from several aspects."

"First, we need to decrease the rate of cesarean delivery associated with a high rate of induction of labor. Cesarean section for dystocia should be avoided before active phase of labor is established, particularly in nulliparous women, induced labor, and VBAC attempts."

He added that there should be a clinically accepted indication for performing cesarean delivery. Also, physicians and patients should be educated about trial of labor in women with a previous uterine scar.

"We agree with ACOG. They have just issued guidelines that call for increased use of VBAC, and we are in accordance with this," he noted.

S. Katherine Laughon, MD, MS, a fellow and maternal–fetal medicine specialist working with Dr. Zhang, said that barriers to VBAC exist but the study was not set up to address the specific reasons why.

"Recently, there was a National Institutes of Health consensus conference on what are the barriers to women getting access to providers and to healthcare facilities that will provide the opportunity for a trial of labor after a prior cesarean section, and also what are the barriers for physicians," Dr. Laughon said. "This particular study does not address that exact question, but it is something that both clinicians and policy makers at the national level need to investigate and find answers for."

Dr. Zhang and Dr. Laughon have disclosed no relevant financial relationships.

Presented August 30, 2010, in a teleconference at the National Institutes of Health.

Am J Obstet Gynecol. Published online August 13, 2010.