Table Summarizing Research Studies Waterbirth

So what IS the evidence on waterbirth?

To answer this question, in April 2014 I conducted a thorough review of the literature on PubMed. I have published my findings online both in this article, and in a more detailed format in the Evidence Based Birth Annotated Bibliography on Waterbirth. I then used the Annotated Bibliography to write this Evidence Based Birth article.

To download the Annotated Bibliography, click here.

To read more about the methods for Evidence Based Birth articles, click here.

The specific keywords for the literature review included “childbirth” AND “water immersion” OR “water birth.” Articles were included in the Annotated Bibliography if they were published in the English language after the year 1993, and if researchers described outcomes from births that occurred underwater.

I included all levels of research evidence on this topic: systematic reviews, randomized controlled trials, prospective observational studies, retrospective survey or scientifically-conducted retrospective audit studies, qualitative studies, and case reports.

I excluded audit reports that did not follow the scientific method. For example, I excluded audits that did not have Institutional Review Board approval or did not report adequate statistics.

Also, if a research study was reported in two separate articles, I only included the most recent version.

After the initial search was conducted, I read through titles and abstract to find out which articles fit the inclusion criteria. If an article was relevant, I obtained and read the whole article. I looked at the reference list from each paper to see if there were any other articles that I should include.

Again, the PDF of the entire 70+ page Annotated Bibliography is available for download here.

The results are summarized here in Table 1 (randomized trials, prospective studies, and retrospective studies) and Table 2 (case reports), in chronological order.

When looking at the studies in Table 1, you can see that there have been more than 28,000 waterbirths documented in research studies since 1991.

In fact, there have been at least 19 studies on waterbirth in the past 20 years, and ACOG/AAP only mentioned six of these in their opinion statement. Out of the six papers that they referenced, they completely misrepresented the results of one study. Thus the vast majority of the research literature on water birth was not covered in ACOG and AAP’s review of the literature.

Table 1: Evidence on Waterbirth

First Author and Year Study Design # Waterbirths & Included in the ACOG/AAP Opinion?
# Land Births


Retrospective 679 women who had waterbirths; no comparison group No


Retrospective survey of maternity units that was completed by phone or mail 4,494 women who had waterbirths, 8,255 women who labored in water and birthed on land Yes, but the study results were  misrepresented


A retrospective survey sent to consultant pediatricians and maternity units 4,032 women who had waterbirths, their outcomes were compared to regional data for low-risk women who had land births (spontaneous vaginal deliveries at term) Yes


Prospective 49 waterbirths; no comparison group No


Case control 301 women who had waterbirths, 301 matched (similar) women who had land births No


Prospective 1,327 women who had waterbirths, compared to a matched group of women in the same unit who did not use the pool No


Retrospective survey study with collection of quantitative and qualitative data 189 women who had waterbirths; no comparison group No


Qualitative interview study 9 women who had waterbirths No


Prospective 3,617 women who had waterbirths, 5,901 women who had land births; all births were spontaneous vaginal births with a single baby in head-down position. Some of the land birth group included women who were planning a waterbirth but had to transfer to land births (n = 647). Yes


Case control Microbiome study: 34 infants born in water, 26 infants born on land after labor in water, 36 infants born on land

Case control study: 100 infants born in water compared to 100 infants born on land without water immersion



Pilot randomized controlled trial 15 women who had waterbirths, 65 land births Yes


Prospective 3,327 waterbirths, 2,763 land births in bed, and 1,049 births on birthing stools No


Prospective 1,600 women who had waterbirths, 515 women who had land births. For most of the outcomes, only women giving birth for the first time were included: 737 women who birthed in the water; 407 in bed; and 142 on a delivery stool. No


Prospective 89 women who had waterbirths, 133 women who labored in water and had land births, 146 women had no water immersion at all. All of these women were interested in waterbirth and met the inclusion criteria for waterbirth. No


Case control study with ultrasound evaluations of the pelvic floor 6 months postpartum 25 first-time mothers who had waterbirths and 27 first time mothers who had land births with no water immersion No


Cochrane review and meta-analysis of randomized, controlled trials 3 small pilot randomized, controlled trials Yes


Pilot randomized controlled trial 53 women who were randomly assigned to waterbirth, 53 women who were randomly assigned to land birth. All women birthed using their assigned method. Yes


Prospective 50 women who had waterbirths and 50 women who had land births No
Retrospective case control study with economic impact measurement 110 waterbirths of women giving birth for the first time, and 110 matched women who had land births No


Prospective 5,192 women who had waterbirths, 3,732 women who labored in water and had land births** No


Prospective 207 women who chose waterbirths, 191 women who had land births with an epidural, and 191 women who had land births with no epidural No


A retrospective study of medical records 819 women who had waterbirth and 5,220 women who had land births in an “alongside” midwifery unit. Women who transferred to the hospital labor and delivery unit during labor were not included. No


Retrospective Case Control 219 women who had waterbirths, 219 matched women who had land births and served as a control group No


Retrospective 191 women who had waterbirths; there was no comparison group No


Prospective 1,519 women who had waterbirths, 986 women who had land births. To compare outcomes between water immersion and land birth, they used data from one site where 114 women used a birthing pool (either had a waterbirth or left the pool before the birth) and 459 women who were eligible to but did not use the pool due to preference or unavailability of the pool.* No


Prospective Number of waterbirths not disclosed, but the overall sample (n = 16,577) of women who gave birth in midwifery settings included a substantial percentage of waterbirths No

*Henderson et al. (2014): Because the “birth pool” group (used for comparison purposes) included women with and without waterbirths, I did not include the Henderson et al. study in any comparisons of waterbirth and land birth.

**Burns et al. (2012): It is impossible to compare most of the results between women who had waterbirths versus women who labored in tub but had land births, because the researchers did not report most results separately. The outcomes were reported all together, with the exception of umbilical cord snap, physiological third stage, and neonatal deaths.

Total # of water births that have been recorded in research studies = 28,283

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