Objective: To ascertain if dye-determined amniotic fluid volume just prior to delivery correlates with fetal acidosis at delivery.
Design: The present was a prospective observational study.
Setting: The study took place at the University of Mississippi Medical Center, Jackson MS, USA.
Population: The population included 100 unlaboured women undergoing an amniocentesis for the assessment of fetal lung maturity before an elective Caesarean delivery between January 1997 and December 2000.
Main outcomes measured: The amniotic fluid volume was estimated by ultrasound measurement and quantified by dye-determined methodology immediately prior to Caesarean delivery. Umbilical cord artery pH was collected at the time of Caesarean delivery.
Results: The predictive accuracy of an amniotic fluid index ≤ versus >5 to identify an umbilical artery pH of <7.20 had a sensitivity of 0%, a specificity of 84%, and a likelihood ratio of zero. None of the dye-determined low amniotic fluid volumes were identified using the single deepest pocket technique. Dye-determined low, normal, and high amniotic fluid volume groups contained a similar number of fetuses with umbilical cord arterial pH <7.20 (P = 0.371), <7.10 (P = 0.460), and <7.00 (P = 0.614). Receiver-operating characteristic curves could not identify any amniotic fluid index from 0 to 18, single deepest pocket from 0 to 12, or dye-determined amniotic fluid volume 100–1900 mL to differentiate between the two newborns with an umbilical cord artery pH <7 from 98 babies with cord pH ≥7.0.
Conclusions: Neither ultrasound estimates nor dye-determined amniotic fluid volumes are predictive of a low umbilical artery pH at delivery.