| Abstract: | Objective: To determine a threshold level of amniotic fluid in low-risk term pregnancies predictive of adverse perinatal outcome. Methods: Prospective cohort study of low-risk patients at term undergoing amniotic fluid volume measurement. Amniotic fluid index (AFI) remained blinded unless ≤ 1?cm or ≥ 25?cm. Primary outcome was a positive fetal vulnerability index (FVI). The last AFI was evaluated as predictor of a +FVI. We estimated that we needed to perform ultrasounds on 620 women. Results: Patients were enrolled through 2004–2008. There were 24 (7.8%) patients delivering a neonate with +FVI. An AFI < 8?cm increased the risk of a +FVI (risk ratio 2.70 [95% CI 1.2, 6.0]; p?=?0.01); however, the area under the receiver operating characteristics curve was 0.60. Enrollment was stopped at 308 patients due to enrollment challenges. Conclusions: An AFI cutoff <8?cm was associated with an increase in FVI outcomes but had a low positive predictive value for a +FVI. Isolated incidentally found low fluid in uncomplicated pregnancies may not be an indication for immediate intervention. |
