Non quantitative estimation of amniotic fluid volume in suspected prolonged pregnancy.

A simple non-quantitative method of assessing the volume of amniotic fluid by ultrasound examination is described. The classification is based on the presence or absence of echo-free space between the fetal limbs and the fetal trunk or the uterine wall. In order to test the value of the classification, 150 patients with pregnancies of 42 weeks or more duration underwent ultrasound examination in the 48 hours prior to delivery. The patients classified as having "reduced" or "absent" amniotic fluid has statistically significant excess incidence of meconium stained liquor, fetal acidosis, birth asphyxia and meconium aspiration. The outcome of patients with "normal" amniotic fluid volume was excellent.