Amniotic fluid volume estimation and the biophysical profile: A confusion of criteria

The biophysical profile (BPP) can be used as an initial test of fetal healt h and as a secondary back-up assessment of fetuses at risk of adverse outco mes when preliminary evaluations are not reassuring. The BPP evaluates five characteristics: fetal movement, tone, breathing, heart reactivity, and am niotic fluid (AF) volume estimation. Three of the most frequently used obst etric textbooks define adequate AF volume differently. In two of the three, the stated method of evaluating AF volume differs from that actually used by the referenced authors. We reviewed articles by Manning and found that h is methodology changed from a 1-cm pocket in one plane to a 1-cm pocket in two perpendicular planes, and finally to a 2-cm vertical pocket with a 1-cm horizontal measurement. The 2 x 2-cm pocket is a fourth methodology that h as been introduced recently. It is not known how often and in which groups each of the four methods has been used to evaluate abnormal AF volumes. The relevance and importance of determining precisely the ultrasound measureme nt actually used for investigations are emphasized by looking at women with AF indices less than or equal to 5. Fifty-three percent of those women had a 2 x 2 pocket, 72% had a 2 x 1 pocket, and 95% had al x 1 pocket. The dia gnosis of low fluid can lead to additional testing, hydration, and interven tion, so the importance of a universal definition linked with pregnancy out comes cannot be overemphasized. (Obstet Gynecol 2000; 96:640-2. (C) 2000 by The American College of Obstetricians and Gynecologists.).