Ultrasound placental grading and amniotic fluid quantitation in prolonged pregnancy.

Serial ultrasound examinations were performed every three to five days to monitor 200 singleton pregnancies with gestations of 42 weeks or longer. Scanning was used to measure the deepest amniotic fluid pool and to grade placental echogenic changes. Oligohydramnios, defined as an amniotic fluid pool less than 30 mm, was detected in 33 patients (17%) and was an indication for intervention. Grade III placenta was found in 53 patients (27%), and no grade could be assigned in 13 (7%). Intrauterine growth retardation and meconium-stained or absent amniotic fluid at amniotomy occurred significantly more often in association with oligohydramnios than with grade III placenta, which was found before spontaneous labor in only 24% of cases. Ultrasound placental grading appears to offer little useful additional information to amniotic fluid quantitation in satisfactory monitoring of prolonged pregnancies.