Babies born underwater face no more risks than babies born in other types of midwife-led births, according to new research from a team of midwives and epidemiologists at Oregon State University.
This study, which was published in the Journal of Midwifery & Women's Health, looked at the outcomes of more than 18,000 births, including 6,534 infants born underwater.
The results challenge a joint opinion by the American College of Obstetricians and Gynecologists and the American Academy of Pediatrics opposing birth underwater.
That opinion recommended that water births only be performed as part of clinical trials.
"We just have a long history of doing birth on land, and while women might like to be in the water, it does pose some interesting questions for the provider who is responsible for her safety,"said Melissa Cheney, an author of the study and a medical anthropologist at OSU and a practicing midwife.
"We found that being born underwater posed no increased risk of mortality, or negative outcome, to newborns."
However, the study did find that mothers who gave birth in the water were somewhat more likely to suffer from genital tears.
Birth centers and some hospitals offer specialized tubs filled with warm water to help women manage the pain of labor. Obstetricians and pediatricians have accepted women immersing themselves during the early stages of labor.
However, they have raised concerns that infants born in the water may be at risk of aspirating water, drowning, or infections, based on individual case reports.
Proponents of water birth say several natural mechanisms, including the dive reflex, protect healthy newborns from inhaling water.
Practitioners on both sides of the debate agree that water births are not appropriate for complicated or high-risk births.
The new OSU study is among the largest-ever of water births, and it's the first large study that examines the practice in the United States.
It drew on data from 2004 to 2009 from the Midwives Alliance of North America Statistics Project, (known as MANA Stats) a national online database of medical records from mid-wife led births.
The study found that babies born underwater performed just as well in tests of their respiration, activity, and pulse in the first few minutes of life. The authors also found no increase in neonatal deaths or hospital admissions for the group born underwater.
The American College of Obstetricians and Gynecologists did not immediately respond to a request for comment.
The Vice President of Women's Health at Legacy Health, Dr. Duncan Neilson, said the methodology of the OSU study was statistically sound. He said could help change attitudes toward water birth in the U.S. -- though he expects that will happen slowly.
"Practitioners in the U.S., especially pediatricians have very little experience with this modality, and therefore they're terrified of being called in to have to resuscitate a drowning newborn," he said.
Neilson said the study will likely face criticism on the grounds that most midwives enter records into the MANA Stats database voluntarily, and that could bias the study's results.
But Neilson and the authors point out that the database is designed to reduce selection bias, by requiring midwives to start entering patient information early in a pregnancy, before the outcome is known.
"They can't hide bad outcomes," he said.
Neilson, who calls himself a traditional obstetrician, did not participate in the study, but he did help establish a water birth program at Legacy's Portland hospitals.
His own beliefs on the practice have evolved.
"My first response to the people who asked me to support water birth program was 'No way, Jose. We don't do that. Humans are land animals. We're not seals or whales,'" Neilson said.
Now Neilson says he supports water birth as a way of making the hospital setting more
inviting to women who find birth overly medical, and want more control over the process.
Neilson says he was concerned that many Oregon women - close to five percent- were choosing to give birth outside the hospital setting, and hospitals were reluctant to admit those patients when emergencies arose, leading to tragic deaths.
When he looked further into the issue, Neilson says he found little concrete evidence of the risks of water birth, and in 2007, he helped Legacy launch its program. Neilson says that about 500 babies in the program have been born in the water.
Oregon Health & Science University has also offered water births for more than 15 years.
Legacy has been subject to at least one lawsuit filed by parents who say they were not adequately informed of the risks of water birth.