(CNN) Cases of Legionnaires' disease have been documented at hotels, gyms and even health care facilities, but a recent report from the Centers for Disease Control and Prevention finds that even newborns are being infected -- after water births.

In two cases in Arizona last year, babies born in home tubs contracted the disease.

In the first Arizona case, the infant was delivered by a midwife in a new birthing tub that had been cleaned with vinegar and filled with tap water just before delivery. The baby was born within an hour of the mother getting into the tub and seemed fine initially.

But the next day, the infant was taken to an emergency room with difficulty breathing. The baby tested positive for Legionella bacteria and was found to have congenital heart disease. The newborn was hospitalized for more than two months, primarily for the heart disease but also to treat the infection.

In the second case, the infant was again delivered at home. The mother had rented a Jacuzzi tub and filled it with tap water, which she kept at 98 degrees for a week before delivering.

Three days after birth, the infant developed a 101-degree fever that persisted through the following day. The baby was taken to an emergency room, where its temperature spiked to 102.6 degrees. Test results were positive for Legionella, and the baby was hospitalized for a week.

In both cases, the Arizona Department of Health found "numerous gaps in infection prevention for water births," noting that tap water itself is not sterile and that Legionella bacteria can grow in plumbing systems. Allowing the water to sit at 98 degrees contributed to bacterial growth in the first case, the agency said.

Expert recommendations

The incidences are rare but not surprising, said Dr. Joseph Wax , chairman of the American Congress of Obstetricians and Gynecologists Committee on Obstetric Practice.

"Waterborne infections with serious, even fatal, infant outcomes are a recognized complication associated with birth underwater," he said. "Appropriate measures, as suggested by the CDC report, will hopefully reduce such risks in women choosing to deliver underwater. Nonetheless, avoiding birth underwater is the best prevention."

The OB/GYN group recommends, however, that women begin labor in water. "Immersion during the first stage labor has been associated with somewhat shorter labors and less frequent use of spinal and epidural analgesia during labor," Wax explained.

But when it comes to actual delivery, the group says no, citing risks such as drowning, infections and snapping of the umbilical cord.

"The frequency with which these occurs is unknown and likely low. However, when they do occur, they can be severe or even fatal in rare instances," Wax said.

Little data to determine safety

In its position statement, the American Congress of Obstetricians and Gynecologists says there simply aren't enough data to determine the safety of water births: "Until such data are available, it is the recommendation of the American College of Obstetricians and Gynecologists that birth occur on land, not in water."

The group also says that the little data available don't show any real benefit to mother or child.

In fact, the number of water births in the United States isn't even recorded.

But Michelle Collins , director of Vanderbilt University's nurse-midwifery specialty, says the numbers are there -- but much of them are observational data, not the double-blind scientific gold standard.

"Despite limitations, the best available research indicates that water birth is associated with perinatal outcomes similar to those expected in a low-risk population," said Collins, who is also a fellow of the American College of Nurse-Midwives

Collins points to data from the American Association of Birth Centers , which tracks delivery data from birth centers across the country. According to the CDC, hospitals still account for 98% of all deliveries, but the data from the AABC show that rates of transfers from birth centers to hospitals after water births are just 1.5%, compared to a 2% transfer rate for those not born in the water.

Out of the 15,574 deliveries followed by the AABC between 2007 and 2010 there were 3998 water births. Of those births, there were "no incidences of pneumonia, sepsis or other respiratory infection following water birth and there were no reports of ruptured umbilical cords or newborns breathing water into their lungs associated with birth underwater," the association says.

of available literature evaluated 3,243 births among 12 trials that found "no evidence of increased adverse effects to the fetus/neonate or woman from labouring in water or waterbirth." Cochrane reviews are internationally recognized scientific literature reviews considered to be of some of the highest scientific standards. In addition, a 2009 Cochrane review of available literature evaluated 3,243 births among 12 trials that found "no evidence of increased adverse effects to the fetus/neonate or woman from labouring in water or waterbirth." Cochrane reviews are internationally recognized scientific literature reviews considered to be of some of the highest scientific standards.

Benefits vs. dangers

"There is a difference between saying 'there is no confirmed associated benefit that we have yet found' versus 'it's dangerous,' " Collins said.

But the Cochrane study also pointed out that further research was needed.

Wax says these observational studies that find a benefit from water births probably overestimate the benefits and underestimate the risks because of confounding factors.

"For example, in cases of planned underwater delivery that go on to deliver out of water, adverse outcomes may be counted as occurring in the out-of-water group. This is not appropriate and can make water birth appear safer than birth out of water," he explained.

Collins believes that much of the hesitation behind water births is not grounded in science at all but is cultural. She points to practices such as continuous fetal monitoring (of the baby), suctioning and a woman giving birth on her back as practices that don't have many studies behind them but are considered normal delivery practices.

But what happens in cases like those in Arizona?

"What we see in the case reports are practitioners not doing a safe job," she said. What's key is that people and institutions follow strict protocols.

In fact, after those two cases, the Arizona Department of Health developed resources and guidelines about how to have safer water births and reduce the risks of Legionella infections.

Mothers should always use a disposable birthing tub rather than a hot tub, it said. In addition, while the risk for Legionella infection cannot be eliminated completely, it can be reduced by running hot tap water through the hose for 3 minutes to clear the hose and pipes of stagnant water and sediment.

What to ask about water births

So what's a mother to do when considering whether to deliver in the water?

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Wax says women need to be educated about the risks, "understanding that these risks cannot currently be quantified but are likely infrequent," he said.

Collins advises checking with the center or hospital workers or the midwife you are working with: What are the protocols in place to ensure a safe water birth? What are the policies? What type of experience do they have in handling water birth? What are the established policies about cleaning tubs?

But ultimately, she says, it's a mother's choice.