Check out the newest water birth study; its a retrospective cohort study and focuses on the risks to the mother and interventions used.1
In this study labors were shorter for water births. This is a normal finding in retrospective studies, my paper on hydrotherapy in labor discusses some potential reasons for this, namely that the labors that “risk out” of giving birth in water tended to be longer.2 This study also reported less use of amniotomy, internal fetal monitoring, and augmentation of labor for women who had a water birth. Again, this makes sense in a retrospective cohort study because women who had issues that may require internal monitoring or augmentation would have been removed from the water. We talked about the bias this introduces to water birth studies in our recently published meta-analysis (You can access the article for free for the month of February).3
What I’m most interested in now is the question of perineal integrity. In this study water birth was protective, but this isn’t true for every study. I’m doing some work with a few data sets I have trying to understand how the methods used in the study may be contributing to the disagreement we see in the literature. The work is a bit “mathy” right now, but I should have a draft ready for publication in a month or two so I’ll keep you posted.