Women should only have a cesarean delivery if there is a medical reason for it, and doctors should not switch a vaginal birth to a cesarean section sooner than recommended, conclude the authors of a new study.

These actions, which are especially important for first-time mothers, should help stop the trend of increasing c-sections in the U.S., the researchers say.

The rate of c-section deliveries has been steadily increasing in the U.S. - jumping from about 1 in 5 births in 1996 to almost 1 in 3 births in 2008. In the new study, Dr. Jun Zhang of the National Institutes of Health and colleagues tracked more than 220,000 deliveries to determine which women gave birth by c-section and why.

Zhang and his colleagues examined 6 years worth of electronic medical records from 19 hospitals across the U.S. For each birth, they analyzed information on the mother’s medical history and the newborn’s health, as well as specific notes from the delivery itself.

In line with other recent studies, they found that about 31 percent of births between 2006 and 2008 were performed by c-section. The rate was similar for both first-time mothers and mothers who had given birth before, the researchers report in the American Journal of Obstetrics and Gynecology.

They also uncovered some possible clues to explain the increase in the rate of c-sections: the procedures were much more likely in older mothers (over 35) than younger mothers, women who had c-sections for their first birth were having them again for their next deliveries, and doctors were switching women over from vaginal deliveries to c-sections earlier than recommended during labor. Obese women also had higher rates of c-section than non-obese women.

There are many reasons for rising rates of c-sections, Dr. Marian MacDorman, who studies birth patterns at the Centers for Disease Control and Prevention in Atlanta, told Reuters Health. “There’s some maternal request,” said MacDorman, who was not involved with the study, “(and) maybe doctors are more comfortable doing cesareans more regularly.”

The new findings suggest that doctors may be “intervening too soon and not allowing an adequate period of labor before calling for cesarean section,” Dr. Mark Landon, chair of obstetrics and gynecology at the Ohio State University College of Medicine, told Reuters Health by email.

C-section is clearly called for in some cases, such as when the fetus has signs of a medical condition or is positioned to be born feet-first.

But for mothers who don’t need a c-section for medical reasons, there is evidence that having a c-section puts babies at higher risk for breathing problems and mothers at higher risk for future pregnancy complications, MacDorman said.

The procedure itself puts mothers at risk of bowel or bladder injury, or for needing a hysterectomy, added Zhang. It also carries a higher price tag than vaginal delivery.

According to the Agency for Healthcare Research and Quality, the average c-section without complications costs about $11,500, more than $5,000 more than the average vaginal birth.

“Cesareans can be life saving and necessary,” Landon said, “yet most would agree that too many are performed.”

The authors say that targeting first-time mothers will be one of the key measures needed to stop the rate of c-sections from increasing further.

Zhang admitted that he and his colleagues were surprised by how high the rate of c-sections was for mothers giving birth for the first time. “The majority of the women who had a previous c-section,” Zhang noted, “would have another c-section” for the delivery of their next children. “Those two factors have pushed the overall c-section (rate) to the current level,” he said.

SOURCE:  American Journal of Obstetrics and Gynecology, online August 13, 2010.