Low amniotic fluid volume is poorly identified in singleton and twin pregnancies using the 2 x 2 cm pocket technique of the biophysical profile

Background, This study was done to determine the accuracy of the 2 x 2 cm p ocket identifying low amniotic fluid (AF) volume in singleton and twin preg nancies. Methods. The AF volume was evaluated by ultrasonography for the presence of a 2 x 2 cm pocket before amniocentesis. The actual AF volume was then dete rmined by a diazo-dye reaction with subsequent spectrophotometric analysis using paraminohippurate. Results, The AF volume was low in 21 of the 79 singleton pregnancies and no rmal in 47; hydramnios was present in 11. Among amniotic sacs of the 60 twi n pairs, oligohydramnios was found in 33 amniotic sacs. normal AF volume in 80 sacs, and high volume in 7. An AF pocket smaller than 2 x 2 cm was iden tified in only 3 of the 79 singleton pregnancies and in only 2 of the 120 t win amniotic sacs. Conclusions. Judging AF volume on the basis of a 2 x 2 cm pocket misses mor e than 90% of cases of oligohydramnios in singletons and twins.