New research from the United States suggests water births are just as safe for newborns as normal delivery, although the choice for expectant mothers isn't so clear cut.
The concept of giving birth in a warm tub instead of a dry hospital bed has been growing in popularity the world over. But in some places, including the US, the practice remains highly controversial; doctors, midwives and hospitals continue to disagree over the evidence.
While going through early contractions in the bathtub is generally considered safe and can reduce the time, stress and pain of labour, actually giving birth underwater is another matter.
Today, evidence on the safety of water births is still limited and no large rigorous studies exist. In fact, most of the research so far has been mostly observational, and depending on where you live, expectant mothers are given completely different advice or no choice at all.
Most retrospective studies have been published in Europe, whereas in the US, the research is largely anecdotal and involves a very small number of clinical cases, which are considered the lowest form of evidence.
As a result, US doctors are wary of promoting the practice, and today, water births are an option in less than 10 percent of all maternity care facilities.
In fact, in 2014 the American College of Obstetricians and Gynecologists (ACOG) and the American Academy of Pediatrics (AAP) issued a joint warning, advising strongly against allowing women to remain in the bathtub after the first stage of labour unless they were part of a clinical study.
But others argue that might be too cautious an approach. Since then, several randomised large studies in the US have found this practice is perfectly safe for the mother and the baby.
When researchers from the University of Michigan analysed 397 water births and 2,025 'land' births from two midwifery practices, they found no difference in risk for either the mother or the child.
Mothers in the water group actually sustained fewer first- and second-degree tears in their birth canal, while newborns were no more likely to enter the intensive care unit or score lower on basic development tests.
"The long and short of it is that if you use proper techniques .. the outcomes are very good," says Lisa Kane Low, who researches evidence based care practices during childbirth at of U-M.
"They mirror what we see in international studies of water birth."
Unlike US organisations, global health groups like the Royal College of Obstetricians and Gynaecologists (RCOG) and the Royal College of Midwives (RCM) support water births for healthy women, as long as they are fully informed of the risks, such as infection or umbilical cord tearing.
According to randomised studies in China, Iran, Australia, South Africa and Europe, however, these risks occur rarely with the right practices.
The University of Michigan study had a sample size too small to pick up on these rare risks. According to some researchers, at least 1,000 people in each group would have a better change of detecting such dangers. However, it does suggest that for most healthy mothers, water births aren't an issue.
Prior to these findings, the largest study in the US found that while home water births do not put the newborn at risk, they could increase genital tract trauma, although it's hard to pin this on an exact cause.
Tears in the genital tract after childbirth can be influenced by a mother's age, how long they pushed for, the size of their babies, and the position they birthed them in.
While some trials have found no difference in tears between water births and land births, others have found an increased risk in warm water, or a decreased risk in warm water. To make things even more difficult, it's also hard to split up the advantages of simply labouring in water versus birthing in water.
An unpublished randomised trial in South Africa had 60 women birth in water without actually labouring in water. And in the end, this group experienced less pain than those who birthed on land with no difference in overall trauma to the birth canal.
Still, only a handful of randomised trials have been conducted in total, probably in part because mothers who really want to have water births are unlikely to risk being thrown in a control group.
More research on this topic is clearly needed, but the authors of the new study say there's enough evidence at the moment to safely allow mothers the choice of a water birth.
"Given the current state of the science surrounding safety of water birth, the suspension of access to water birth in the hospital setting because of the absence of a clinical trial is unwarranted," they write.
"Consistent with other care options and interventions during childbirth, families can be supported to make informed choices about what best safely meets their needs."
The study was published in Birth.