Introduction: Two techniques for sonographic evaluation of amniotic fluid are Amniotic Fluid Index (AFI) and Single Deepest Pocket (SDP).  In this study,we aimed to determine the accuracy of AFI and SDP in predicting prolonged pregnancy outcomes.
Methods: In this prospective, double-blinded, cohort study, 362 women with more than 40 weeks of gestational age were evaluated. Both AFI and SDP methods were used for all patients. Pregnancy-related outcomes and complications including meconium-stained amniotic fluid (MSAF), 5-minute Apgar score, Neonatal Intensive Care Unit (NICU) admission, necessity of cesarean section, and mortality rate were evaluated. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were also calculated.
Results:Sensitivity and specificity of AFI in the diagnosis of MSAF were 68% and 47%, respectively; the rates were higher than those of SDP. Compared to SDP, AFI was more sensitive for predicting the necessity of cesarean section (85% vs. 68%). No association was found between abnormal 5-minute Apgar score and abnormal AFI or SDP.
Conclusion: Compared to SDP, AFI is a better method for predicting MSAF and necessity of NICU admission or caesarian section.