Do semiquantitative amniotic fluid indexes reflect actual volume?

OBJECTIVE: Our objective was to determine how well semiquantitative ultrasonographic measures of amniotic fluid, i.e., maximal amniotic fluid vertical pocket and amniotic fluid index, reflect actual amniotic fluid volumes in 50 near-term patients whose amniotic fluid volume estimates were normal by visual inspection. STUDY DESIGN: Before amniocentesis for fetal lung maturity, each patient had visual amniotic fluid volume estimates, maximal amniotic fluid vertical pocket, and amniotic fluid index performed by the same examiner, and then each received intraamniotic injection of a 10% paraaminohippurate solution. Amniotic fluid volume was quantitated by spectrophotometric assay of paraaminohippurate concentration. Oligohydramnios and polyhydramnios were defined as < 300 and > 2000 ml, respectively. RESULTS: Quantitative amniotic fluid volume was positively related to both amniotic fluid index and maximal amniotic fluid vertical pocket (r = 0.75 and 0.60, respectively). True-positive rates for oligohydramnios (amniotic fluid index < 5 cm or maximal amniotic fluid vertical pocket < 2 cm) were 100% and 0%, respectively; false-positive rates with either method were 0%. True-positive rates for polyhydramnios (amniotic fluid index > 20 cm and maximal amniotic fluid vertical pocket > 8 cm) were 0%; false-positive rates were 16% and 24%, respectively. CONCLUSIONS: Amniotic fluid index appears to be slightly better than maximal amniotic fluid vertical pocket for reflecting actual amniotic fluid volume. Both indirect methods tend to overestimate actual amniotic fluid volume at the upper end of its extremes.

Antepartum fetal assessment in hypertensive pregnancies.

Antepartum fetal assessment in hypertensive pregnancies helps to prevent perinatal morbidity and mortality. The pathophysiology of chronic maternal hypertension often leads to placental insufficiency and fetal growth retardation. Current testing schemes include serial ultrasonographic assessment of fetal growth, placental morphology, and amniotic fluid volume; fetal heart rate testing using either non-stress or contraction stress methods; multiple parameter biophysical profile; and Doppler flow velocimetry of fetal umbilical and maternal uterine arteries. The values of individual and combined testing approaches are evaluated and an integrated scheme for fetal management, illustrated by case examples, is presented.

The effects of epidural anesthesia on the Doppler velocimetry of umbilical and uterine arteries in normal and hypertensive patients during active term labor.

To study the effects of epidural anesthesia on uterine and umbilical artery blood flow in preeclampsia, we observed 25 patients in active labor at 36 or more weeks' gestation. Seven had preeclampsia, eight had chronic hypertension, and ten had no complications. Doppler velocimetry of the uterine and umbilical arteries was performed before and after intravenous fluid loading and at 30 and 60 minutes after epidural blockade. Maternal vital signs and fetal heart rate were monitored continuously. After epidural block, mean maternal blood pressure fell significantly in all groups, but no maternal hypotension was observed. Mean maternal and fetal heart rates were unchanged. After epidural block, mean uterine artery systolic-diastolic (S-D) ratios did not change in the chronic-hypertension and normal groups, but fell significantly in the preeclamptic group to values similar to those of the normal group. Umbilical artery S-D ratios did not change in any group. In preeclamptic pregnancy, epidural anesthesia may help to reduce uterine artery vasospasm and may benefit intrapartum fetal well-being.