Sitting in a tub of warm water can relieve a mom-to-be's pain during the early stages of labour, but actually giving birth under water has no proven benefit and may be risky, say recommendations for U.S. obstetricians.

There's no count of how many babies in the U.S. are delivered in water, but it is increasingly common for hospitals to offer birthing pools or tubs to help pregnant women relax during labour.

Birth as Art

Brooklyn-based performance artist Marni Kotak leans on a birthing pool. It is increasingly common for hospitals to offer birthing pools or tubs to help pregnant women relax during labour. (Kathy Willens/Associated Press)

In a report released Thursday, a distinction is made between the two uses, saying that early on immersion may be helpful, as long as some basic precautions are taken.

But there has been little scientific study of underwater delivery, along with a handful of reports over the past decade or so of near-drownings and other risks to the infant, said the joint opinion from the American College of Obstetricians and Gynecologists and the American Academy of Pediatrics.

Although complications appear to be rare, the report urges that underwater deliveries be performed only in research studies to settle the questions.

"Labouring in water is not the same as delivering under water," said co-author Dr. Jeffrey Ecker of Harvard University, adding that he's cared for numerous women comforted by immersion during labour.

As for delivery, "We want people to do more research," added ACOG committee member Dr. Aaron Caughey of Oregon Health & Science University.

In fact, midwives at Caughey's hospital perform several dozen underwater deliveries a year and are collecting data on how mothers and babies fare, said Cathy Emeis, a certified nurse-midwife at the Oregon university. She cautioned that the numbers are small but so far don't show increased risks.

Pregnant women interested in a water birth at the Oregon facility are required to take a special class and sign a consent form, Emeis said.

"We always acknowledge to our patients that there is not a lot of high-quality evidence that shows there's a benefit to birthing under water," she said.

Thursday's recommendations aren't binding. Birthing in warm water, which proponents say simulates the uterine environment, has been an option for several decades, although more women use it for early labour than delivery, said Tina Johnson of the American College of Nurse-Midwives.

"I don't know that this statement will necessarily change women's desire for that option," said Johnson, whose organization is drafting its own guidelines.

The Canadian Association of Midwives told CBC News it is standard practice for midwives in Canada to offer underwater deliveries. 

"In our experience and our understanding of the research to date, there's no major concern around the safety of water birth for healthy, normal pregnancies and healthy, normal labour and birth," Elizabeth Brandeis of the Ontario Association of Midwives said in an interview.

"The majority of women I work with gravitate towards water at some point during their labours." Brandeis called the U.S. appeal for more research "a laudable impulse."

The U.S. report recommends that hospitals or birth centres choose low-risk candidates for immersion during labour, keep tubs clean, monitor women appropriately and be able to move them out of the water quickly if a problem occurs.

It says potential risks of underwater delivery include infection, difficulty regulating the baby's body temperature and respiratory distress if the baby inhales water.