[The pressure of amniotic cavity during pregnancy and treatment of unruptured oligohydramnios with antepartum amnioinfusion].

OBJECTIVES

To measure the pressure of the amniotic cavity during pregnancy and to study the effects of antepartum amnioinfusion on oligohydramnios with intact membranes.

METHOD: We used an improved three-way switch apparatus to measure 110 women during pregnancy, and treated 97 oligohydramnios with antepartum amnioinfusion or intravenous infusion as controls.

RESULTS

The pressure of the amniotic cavity was 1.69 +/- 0.23 kPa, which was close to the normal value in pregnancy. In oligohydramnios, it was 1.1 +/- 0.3 kPa, and in polyhydramnios 3.2 +/- 0.3 kPa(P < 0.01-0.001). When 300 ml fluid was amnioinfused, the amniotic fluid index (AFI) increased by 5.0 +/- 1.8 cm, the pressure of amniotic cavity increased by 0.18 +/- 0.2/kPa and the incidence of vaginal delivery was 87.9%, whereas that of the control group was 12.1%. There were no fetal distress, asphyxia neonatorum, amnionitis or ruptured membrane.

CONCLUSIONS

The pressure of the amniotic cavity during normal pregnancy was stable, but changed with AFI. Antepartum amnioinfusion for unruptured oligohydramnios resulted in a marked increase in incidence of vaginal delivery, a decreased ratio of cesarean section and a reduction of perinatal morbidity. These differences are highly significant.