THROUGHOUT her pregnancy, Susana Hellmuth, 35, felt as if she were walking on eggshells. The Culver City woman had had two previous miscarriages, one heartbreakingly late, just as she entered her third trimester. This time, as a precaution, she spent the final six months in bed. Finally, a few weeks before her due date, she asked her doctor to schedule a caesarean section.

"After six months of not doing anything, the last thing I wanted was complications at birth," she says.

Dr. Chalil Tabsh, her physician and the medical director of the perinatal center at Santa Monica-UCLA Medical Center, said Hellmuth probably would have had a successful vaginal delivery. But he adds: "I think if somebody can decide to step into a plastic surgeon's office and have her breasts enhanced — unindicated surgery — she can have an elective C-section."

Surgical childbirth — in existence since ancient times and made increasingly safe after the advent of anesthesia and antibiotics — has saved the lives of untold millions of women and their newborns. But more women than ever are now making it a personal choice, opting to never feel a labor pain, never practice Lamaze breathing, never be coached to push.

The trend has been fueled by evolving medical opinions and new research.

In 2003, the American College of Obstetrics and Gynecology said that physicians are ethically justified in acquiescing to a woman's request for the surgery, provided the patient understands all the risks. That stance opened the door to making elective surgery a legitimate alternative for healthy pregnant women to discuss with their doctors.

Meanwhile, some research has suggested that vaginal delivery creates its own risks and that C-sections help women avoid incontinence and other health problems down the road.

Even newer studies are beginning to compare the risks of vaginal delivery not with emergency C-sections, as most previous research has done, but with planned surgical deliveries. C-sections are safer, some researchers are finding, without the last-minute rush to surgery after an exhausting trial of labor.

But critics of elective C-sections see a downside. Such research is early and conflicting, they say, and science doesn't yet understand the time-honored trip down the birth canal. Babies delivered by caesarean section have more respiratory infections later in life, and may have more gastrointestinal tract problems as well. And errors in predicting the due date could result in a baby born earlier than the full-term range of 38 to 41 weeks.

Still, elective caesarean is beginning to have a small but noticeable effect on the growing number of C-sections overall.

In one study, conducted from 2001 through 2003, the last year for which statistics are available, 127,762 American women in 17 states chose the knife over waiting for the first pains of labor — 25,140 of them in California.

The numbers, issued in a September 2005 report by Health Grades Inc., a healthcare ratings service, represent 2.55 percent of births in the United States, up from 1.87 percent in 2001. Dr. Samantha Collier, vice president of medical affairs for the service, has reported on elective caesareans for three years. "The first two research findings were not a fluke," she said. "We're seeing significant growth rates year after year."

The increase in elective C-sections comes amid a rise in C-sections overall. In 2004, close to 30 percent of all births were caesarean, up from about 20 percent in 1996.

Often, women needing C-sections are wheeled into a surgical suite after labor has begun, because the baby is too big, too small or not getting enough oxygen or the mother is bleeding heavily. The most prevalent reason women have C-sections is because they've already had one. Vaginal birth after a previous caesarean, termed VBAC, is medically possible, but the number of such procedures is falling. Those women have increased risks, including hemorrhaging from the previous incision, and physicians and hospitals have grown wary of lawsuits.

Some 80 percent of obstetrical lawsuits claim that an indicated caesarean was not done or was done too late, says Dr. Jeffrey Phelan, a Pasadena obstetrician who is also an attorney.

Today, nearly 90 percent of women who have had a C-section deliver their next babies surgically, up from a low of 72 percent in 1996.

Amid this growing overall trend, the number of elective C-sections is only likely to increase.

Hellmuth, for one, is a firm believer in surgical intervention.

On Dec. 18, in a surgical suite at the medical center, her son Nicholas arrived through an abdominal incision, full term, normal and healthy.

For the caesarean to be considered elective, the woman decides on surgery well before her water breaks. Labor has not begun at the time of the scheduled surgery, and there is no precipitating medical problem.

Whether out of a fear of pain, fear of damage to their own internal organs from vaginal delivery, fear for the baby's safety or a need for control, women who have an elective C-section do not go through the time-tested ordeal of labor and delivery.

For Karen Tse-Chang, 37, the choice was based on flashbacks to hemorrhoids after the 2001 vaginal birth of her first child. Her pregnancy had gone smoothly. Labor was short, delivery uncomplicated. No surprises — until she tried to sit. "I got home. I couldn't sit. I couldn't lie down. I could barely move. It was agony," she says. Never again, she thought.

So when she got pregnant with her son two years later, she asked well in advance to have a caesarean section, even though hemorrhoids don't rise to the level of a medical complication requiring a C-section. "It was well planned. I looked at the calendar and said, OK, this is a good day," she says, picking 10 days before she was due. "I knew I was trading one pain for another. But at least with surgical pain, I could take pain medicine," she says.

For her, recovery from the incision was more painful than she expected — but no worse than her experience with hemorrhoids. "I don't see any difference, natural or C-section, as long as you know what you're getting into."

Caesarean and vaginal births each have advantages and drawbacks for the woman, for the baby and for future pregnancies.

In the United States, the overall infant mortality rate is 6.9 per 1,000 babies; the maternal mortality rate is 11.8 per 100,000 live births, and estimates are that a C-section more than doubles the mother's risk of death.

When an infant dies in childbirth, it can take a court of law to figure out if a different birth process would have made a difference.

But in the overwhelming majority of childbirths in the United States, mother and baby do just fine, regardless of the method of delivery.