Measurement of amniotic fluid volume: accuracy of ultrasonography techniques.
OBJECTIVE
Our purpose was to determine amniotic fluid volume by the dye-dilution technique and compare it with the amniotic fluid index, largest vertical pocket, and two-diameter pocket (defined as vertical x horizontal of the largest vertical pocket).


METHODS
This prospective study involved 40 women undergoing amniocentesis in late pregnancy to detect fetal lung maturity or evidence of chorioamnionitis. The amniotic fluid volume was quantified ultrasonographically by means of the amniotic fluid index, largest vertical pocket, and two-diameter pocket. During amniocentesis the fluid volume was calculated by the dye-dilution technique of Charles and Jacoby.


RESULTS
Ultrasonographic measurements by amniotic fluid index, largest vertical pocket, and two-diameter pocket correctly predicted normal amniotic fluid and hydramnios (74%). A new measurement, two-diameter pocket, gave a significantly more accurate estimate of oligohydramnios than did amniotic fluid index (p < 0.002) or largest vertical pocket (p < 0.0003).


CONCLUSIONS
All three indices are moderately accurate in identifying normal amniotic fluid volume and hydramnios. Two-diameter pocket is the most accurate test to predict oligohydramnios.
Magann
E F
EF
Department of Obstetrics and Gynecology, University of Mississippi Medical Center, Jackson 39216-4505.
Nolan
T E
TE
Hess
L W
LW
Martin
R W
RW
Whitworth
N S
NS
Morrison
J C
JC
D000293:Adolescent; D000328:Adult; D000653:Amniotic Fluid / Q000000981:diagnostic imaging*; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D007201:Indicator Dilution Techniques / Q000592:standards; D016104:Oligohydramnios / Q000000981:diagnostic imaging; D011247:Pregnancy; D012372:ROC Curve; D014463:Ultrasonography / Q000379:methods / Q000592:standards*