Correlation of Ultrasound Estimated with Dye-determined or Directly Measured Amniotic Fluid Volume Revisited

Background/aims: To examine the relationship of the amniotic fluid index (AFI) and single deepest pocket (SDP) with an AFV as modelled by Brace or Magann.

Methods: AFI and SDP were evaluated for their correlation with an actual AFV using the Spearman correlation coefficient.

Results: 482 AFI and 468 SDP pregnancies were evaluated. There was a significant association between the AFI and SDP and an actual AFV (p < 0.0001). The AFI range of 5.1-20 was better correlated than 5.1-24 for normal AFVs Brace (κ = 0.175) and Magann (κ = 0.356) versus 5.1-24 (κ = 0.150 and κ = 0.319), respectively. The agreement level t for the AFI (κ = 0.175) and SDP (κ = 0.126) using Brace was slight and for the AFI (κ = 0.356) and SDP (κ = 0.295) using Magann was fair.

Conclusions: Both the AFI and SDP were correlated with actual AFV using both models. AFI of 5.1-20 better categorizes normal volumes. Although the Magann model correlates AFI/SDP and AFV better, the superiority is minimal.