The evidence for abandoning the amniotic fluid index in favor of the single deepest pocket

This study assessed whether the amniotic fluid index (AFI) or the single deepest pocket (SDP) is the best technique to estimate amniotic fluid volume. The AFI and SDP were compared to a dye-determined or directly measured amniotic fluid volume. A PUBMED search from 1990 to 2006 was conducted using the search terms "single deepest pocket" or "largest vertical pocket" or "maximum vertical pocket" or "2X1 pocket" AND "amniotic fluid index". One study compared the AFI and SDP to a dye-determined amniotic fluid volume. There were 1219 publications that used the search term SDP-LVP-MVP versus 4378 using AFI. Twenty publications contained both the AFI and SDP, but only six compared the AFI and SDP. Both the AFI and the SDP poorly identified abnormal amniotic fluid volumes, and neither technique was superior to the other. The AFI identifies a significantly greater number of women as having oligohydramnios versus the SDP but without any difference in perinatal outcomes. Compared with SDP, AFI excessively characterizes a greater number of pregnancies as having oligohydramnios leading to more interventions without improvement in perinatal outcome. The AFI should be abandoned and the SDP used to estimate amniotic fluid volume.