Barnett and Humenick (1982) found that long, hard valsalva pushing during second stage increased fetal acidosis. Women with normal pregnancies in first stage of labour (n=10) were randomly assigned to either: a long valsalva closed-glottis pushing group (breathholding for ten seconds while pushing); or a short open-glottis pushing group (allows exhalation while bearing down). Neonatal outcomes were