[Clinical application of ultrasonographic indexes for assessment of amniotic fluid volume]

To find the favorable interval of assessment of amniotic fluid volume and the optimal standard for oligohydramnios.

To determine actual amniotic fluid volume (AAFV) by collecting amniotic fluid during cesarean section and compare it with maximum vertical pocket (MVP) and amniotic fluid index (AFI) in different interval between cesarean section and measurement and test the sensitivity and specificity of MVP and AFI of different standard.

The ultrasonographic results were divided into three groups according to the interval between measurement and delivery: within 24 hours group, 24-96 hours group and longer than 96 over hours group. The results of the within 24 hours and 24-96 hours groups were positively correlated with AAFV, while the results of the group longer than 96 hours were not statistically significant. The correlation coefficients were 0.840 and 0.869 for MVP, 0.789 and 0.874 for AFI respectively. The receiver-operator characteristic curve showed that MVP < 4 cm and AFI < 10 cm were superior to any other standards to scan oligohydramnios. The sensitivity of these standards was 0.76 and 0.61, and the specificity was 0.83 and 0.91.

It is highly recommended to estimate the amniotic fluid of high risk pregnant women, women with MVP < 4 cm or AFI < 10 cm and with a pregnancy week > 40 weeks should be monitered by ultrasonography every four days.