Waterbirth: characteristics and outcomes in low risk women and babies: a retrospective population cohort study in England 2015/16.

Background Little is known about the incidence of delivery in water and concerns have been raised about the effects of waterbirth on women and their babies as it becomes more popular. Aims and objectives of the study To identify the proportion of low risk women who give birth in water. To compare the characteristics and outcomes of low risk women and their babies who give birth in water with women who do not. Methods Ethical approval was not required as data from maternity information systems was linked to Hospital Episode Statistics for births in England from 1/4/15 -31/3/16. The cohort was restricted to singleton, term vaginal livebirths without instrument, in women with no risk factors requiring obstetric care, in trusts with complete data for birth in water. Multivariate logistic regression models were used to examine maternal characteristics and outcomes (PPH ≥1500ml, OASI) and neonatal outcomes (Apgar <7 at 5 mins, NNU admission). Findings Of 52,476 births, 7099 (13.5%) were recorded as having occurred in water. Water birth was more likely in older women (adjOR for age group 30-34 1.3, 95% CI (1.2,1.5), 35-39 1.3 (1.1,1.4)) and less likely in women of black (adjOR 0.42 (0.35, 0.94)) or Asian (0.26 (0.23, 0.31)) ethnicity, or of lower socioeconomic status (lowest quintile, adjOR 0.50 (0.45-0.55)). There was no association between delivery in water and low Apgar score (adjOR 0.99 (0.70,1.39)) or OASI (adjOR 1.09 (0.94,1.28)). There was a small association with reduced admission to a NNU (adjOR 0.91 (0.84,0.99)) and PPH (adjOR 0.69 (0.53,0.89)); however, in a subset who gave birth in a midwife-led setting, this effect did not persist. Conclusions and implications There is no evidence of harm to the mother (PPH, OASI) or the baby (low Apgar, NNU admission) from waterbirth. Small differences in rates of admission to NNU and PPH may be explained by unmeasured confounding variables from events during labour. Why some groups of women are less likely to experience waterbirth may reflect women‘s choice, or inequitable access.