Amniotic fluid volume in normal pregnancy: comparison of two different normative datasets

Abstract

Aim: The aim of the present study was to compare the two normative datasets of amniotic fluid volume (AFV).

Material and methods: The similarity of the two datasets to classify AFV as oligohydramnios, normal, and polyhydramnios based on fixed cut-offs, stratified by gestational ages (<24 weeks, 24-33(6/7), 34-36(6/7) , and >37 weeks, and to identify oligohydramnios/small for gestational age (SGA) and polyhydramnios/large for gestational age (LGA) was evaluated.

Results: Of the 209 pregnancies assessed, the AFV was 94 ≤ 500 mL, 101 between 501 and 1999 mL, and 14 ≥ 2000 mL. The datasets were in agreement classifying the AFV as oligohydramnios, normal, and polyhydramnios in 76% of the pregnancies. Brace classified more overall patients with oligohydramnios (19%) versus Magann (3%) (P < 0.001). In term pregnancies (>37 weeks), Brace was more likely to classify pregnancies with oligohydramnios (15%) than Magann (3%) (P = 0.004). The likelihood ratio (LR) to detect oligohydramnios/SGA was greater with Magann (LR 12.9) versus Brace (LR 2.75).

Conclusion: The two datasets classify AFV differently in 24% of cases. Brace's dataset is more likely to categorize patients as having oligohydramnios and Magann's dataset is a more useful test for oligohydramnios/SGA identification.