Amniotic Fluid Volume Estimation from 20 Weeks to 28 Weeks. Do You Measure Perpendicular to the Floor or Perpendicular to the Uterine Contour?

Figures & data

Table 1 Descriptive Statistics for Study Population (N = 160)

Variable	Statistic
Maternal age, mean ± SD	27.98 ± 6.39
Race/ethnicity, N (%)
White	94 (58.75%)
Non-White	66 (41.25%)
Parity, median [Q1, Q3]	1 [0, 2]
Gravidity, median [Q1, Q3]	2 [2, 3.5]
AFI perpendicular to the floor, mean ± SD	15.04 ± 3.15
AFI perpendicular to the uterine contour, mean ± SD	17.05 ± 4.15
SDP perpendicular to the floor, mean ± SD	5.11 ± 1.18
SDP perpendicular to the uterine contour, mean ± SD	5.75 ± 1.38

Table 2 Pearson’s Correlation Coefficient and Intra-Class Correlation Coefficient with Bootstrap Confidence Interval

	AFI		SDP
Population	Correlation (95% CI)	ICC (95% CI)	Correlation (95% CI)	ICC (95% CI)
Gestational age <28 weeks	0.67 (0.57–0.74)	0.56 (0.49–0.63)	0.47 (0.34–0.58)	0.42 (0.31–0.52)

Notes: 95% CIs for Pearson’s correlation coefficients are based on Fisher’s transformation; 95% CIs for ICCs are based on bootstrap CIs.

Figure 1 Scatterplot of AFI and SDP estimates based on measures perpendicular to the floor versus uterine contour.

Figure 2 Bland-Altman plot for AFI, with the representation of the limits of agreements.

Figure 3 Bland-Altman plot for SDP, with the representation of the limits of agreements.