The value of ultrasound measurement of amniotic fluid volume in the management of prolonged pregnancies.

Ultrasound assessment of amniotic fluid volume was used to monitor 335 patients with prolonged pregnancy. Reduced amniotic fluid was diagnosed when no single vertical pool of amniotic fluid measured greater than 30 mm. Sixty-five patients with reduced amniotic fluid had labour induced while 270 patients with normal amniotic fluid were managed expectantly unless the cervix was favourable. Patients with reduced amniotic fluid had a statistically significant increase in meconium-stained amniotic fluid and growth-retarded babies and were more likely to require delivery by caesarean section for fetal distress. There were no perinatal deaths in the series and the perinatal outcome was satisfactory in both groups. Ultrasound measurement of amniotic fluid represents an effective discriminatory test in post-term pregnancy.