The intensifying contractions were three minutes apart as Lynn Griesemer tried to reassure her 11-year-old daughter, who hovered anxiously beside her. Her husband, Bob, had not returned the four increasingly urgent messages she'd left on his cellphone and had neglected to give her his new office number at the Pentagon. The couple's sixth child would be born that Friday in June 2002 and Griesemer was worried he might not make it in time.

She regarded his role as central and expected him to do more than act as chauffeur and supporter. After a frantic hour battling rush-hour traffic on Interstate 66, Bob Griesemer burst through the front door of their modest suburban Virginia home and sprinted down the hall to the master bedroom. Less than 30 minutes later, their son Michael, who weighed 10 pounds, was born just as his parents planned: without assistance from a doctor, nurse or midwife. As he had five years earlier when their fifth child was born in their bed, Bob Griesemer caught the newborn and cut the umbilical cord.

"It was the highlight of our life and the highlight of our marriage," recalled Lynn Griesemer, a 44-year-old former Army officer whose four older children were born in hospitals. "An unassisted birth hammers home what it means to be a woman."

One of the leaders of a fledgling movement to encourage unattended home birth, Griesemer said she is unfazed by the reaction she often encounters when people learn about her last two deliveries.

"People think you're a freak," she says matter-of-factly.

Yet in the view of Griesemer and other advocates of the practice — also known as "freebirth"; "UC," for unassisted childbirth; and "DIY (do-it-yourself) birth" — solo birth is superior to the unnecessary interventions that characterize hospital deliveries and the intrusive presence of midwives.

For these women, out-of-hospital births are not accidents of timing, but deliberate expressions of their values. For most, a desire to retain control over one of life's most emotional, intimate and primal processes is paramount.

"Childbirth is a natural event, and I really don't need all the technology," said Griesemer, who, like many freebirthers, shuns doctors and opposes routine immunizations for her children. Unassisted birth, she adds, allows the husband to play a central, rather than a supporting, role and is better for the whole family.

But the freebirth phenomenon alarms many obstetricians, midwives and feminist health experts, who characterize the practice as ill-advised at best — and life-threatening at worst. One called it "a kind of hubris."

The practice, they say, can result in devastating injuries: brain damage, hemorrhage, infection — even death. In the view of many critics, the phenomenon has been given a significant boost by the Internet, which has lent legitimacy to a fringe practice and enabled like-minded women to find each other. To critics it represents a foolhardy repudiation of medical advances that cut infant and maternal mortality in the United States by 90 percent during the 20th century.

Some experts worry that vulnerable or gullible women will be misled into thinking that giving birth alone at home is a viable, even reasonable, alternative. These mothers, they maintain, may not understand that calling 911 — which many homebirthers cite as their emergency backup — is a poor contingency plan when every second counts.

"Obviously we don't think unassisted home birth is a good idea," said Judy Norsigian, executive director of Our Bodies Ourselves, a pioneering feminist health group based in Boston.

"There are deaths from these births that I personally know of," Norsigian said, most of which are preventable and resulted from the failure to recognize clear-cut warning signs: decelerations in the fetal heart rate, indicating respiratory distress; a breech position, in which the baby is sideways or feet first; and umbilical cord abnormalities, which can lead to brain damage or stillbirth.

"People don't report the bad stuff" about unassisted birth, said obstetrician-gynecologist Helain Landy, a high-risk pregnancy specialist who chairs the OB-GYN department at Georgetown University Medical Center. "The biggest argument against this is the unpredictability of events during labor. I've seen completely normal situations turn unexpectedly bad very quickly."

Freebirthers find such arguments unpersuasive.

"Babies die in the hospital," said Heather Jones, 27, the wife of a Navy boatswain's mate who gave birth to her third child in February at her Chesapeake, Va., home, with her husband and mother in attendance. Jones said her decision to freebirth was motivated in part by an unhappy experience delivering her first child in a hospital.

One of the most serious risks is maternal hemorrhage, which can be fatal in a matter of minutes, said Sarah Kilpatrick, chair of the committee on obstetric practice for the American College of Obstetricians and Gynecologists. The college "strongly opposes" all home births on safety grounds.

"Obviously women are adults and can make their own decisions, but do they really understand what the risks are?" asked Kilpatrick, who chairs the OB-GYN department at the University of Illinois at Chicago.

Mairi Breen Rothman is a suburban Maryland certified nurse-midwife who gave birth to two of her four children at home with "lots of midwives" in attendance. Rothman, a spokeswoman for the American College of Nurse-Midwives, said that expert guidance for women in labor is crucial — and is best provided by a trained professional, not a self-educated layperson.

"For a healthy woman, the overwhelming likelihood is that unassisted birth will be fine," Rothman said. "But a woman having a baby is not in a position to be monitoring herself."

No one knows how many women give birth at home by choice without medical assistance, nor are there any studies of the safety of the practice. Of the 4.1 million babies born in the United States in 2004, the National Center for Health Statistics reports that more than 7,000 were born at home without a midwife or physician.

All five of Laura Shanley's children, who range in age from 20 to 28, were born at home. Shanley, 49, of Boulder, Colo., is founder of an influential 10-year-old Web site, Bornfree, and is widely regarded as the American leader of the freebirth movement, which also has proponents in Great Britain, Canada and Australia.

She credits her interest in the subject to the influence of her husband, whom she met as an 18-year-old college freshman. David Shanley, a decade older, was impressed by the writings of the late British obstetrician Grantly Dick-Read, a pioneer of the natural childbirth movement who extolled the benefits of minimal intervention by doctors.

"At the time, I never wanted kids, and I was terrified of childbirth," Shanley recalled in an interview. But a few years later, when she became pregnant, Shanley said she agreed to try an unassisted home birth at her husband's behest, much to the horror of her father, a prominent physician from whom she was later estranged for many years largely over her decision to freebirth. (They have since reconciled, Shanley said.)

On her Web site and in a 1994 book, "Unassisted Childbirth," Shanley describes each birth in unsparing, sometimes graphic, detail. She said she caught one baby herself, pulled another out by his feet and gave birth to a third alone while her toddler sons slept in the next room, then cut the cord herself.

A fourth child didn't make it. Four weeks premature, he was born in the bathroom while Shanley's 19-month-old daughter stood beside her. He died a few hours later of a heart defect, pneumonia and sepsis. Shanley said the coroner told her a hospital birth wouldn't have made a difference.

In Shanley's view, many of the problems during birth are caused by the over-medicalization of a natural process.

"I believe the baby is in distress because the mother is being interfered with and terrified," she said. "You can have a better birth if you don't stand in your own way, or have other people stand in your way. Why is it so extreme to trust yourself?"

To Rothman, the nurse-midwife, Shanley's beliefs underscore a more fundamental problem with maternity care. "To me the really interesting question is, Why would someone go outside the system?" Rothman said. "What is so broken that they don't want to use it?"