Amniotic Fluid Measurement: Agreement Between Emergency Medicine and Obstetrics Physicians

Ultrasonic measurement of amniotic fluid volume helps predict the risk of cord compression, fetal distress, preterm birth, and still birth. We trained emergency physicians (EP) to measure the deepest vertical pocket (DVP) of amniotic fluid and determined the agreement between EP and OB/GYN resident physician measurements of DVP.

We conducted a prospective, observational study to determine whether EP physicians could be trained to measure DVP, which estimates amniotic fluid volume. Three ultrasound trained EPs received a 1-hr didactic training session on how to measure the vertical pockets in all 4 abdominal quadrants to determine the deepest pocket. This was followed by measurements of DVPs in a convenience sample of 45 gravid patients. Independent, paired measurements were made on all patients by a trained EP and an OB/GYN resident blinded to each other’s measurements. All US images were reviewed by an US-trained OB/GYN attending physician and were graded as appropriate, under, or overestimated DVP. Mean DVP measurements were compared using a paired T-test. Percentages of appropriate measurements were compared with a Chi square test. Correlation between EP and OB/GYN measurements was calculated with Pearson’s test. Bland Altman analysis was used to assess agreement between EP and OB measurements.

There were 45 2nd and 3rd trimester patients. The mean (SD) age was 31.8 (5.5). Mean (SD) DVP was 5.2 (1.8) and 5.1 (1.8) cm for EP and OB/GYN respectively (mean difference 0.1, 95%CI, -0.6 to 0.9). The percentages of appropriate measurements were 71% and 81% for EP and OB/GYN physicians respectively, P=0.28. The mean bias was 0.11, limit of agreement -2.84 to 3.05 cm. Pearson’s correlation coefficient was 0.66 (P<0.001).

There were no significant differences between EP and OB/GYN resident measurements of DVP and the percentages of appropriate DVP measurements. There was a good correlation between EP and OB/GYN measurements suggesting that EPs can be trained to measure DVP.