American obstetricians performed a retrospective review of the literature on the complications that could be associated with water birth. The review revealed 74 articles regarding water births. The authors found 16 citations that described complications that were associated with underwater birth. Possible complications that were associated with water birth included fresh-water drowning, neonatal hyponatraemia, neonatal waterborne infectious disease, cord rupture with neonatal haemorrhage, hypoxic ischaemic encephalopathy and death. The systematic review did not identify an adequately controlled trial of delivery under water (second stage of labour underwater) compared with delivery in air.