A, Discriminant analysis group classification for the nonpregnant (NP) and pregnant groups, using the ultrasound measures of SD, AC, and SSF for the predicted group (Wilks λ = 0.187; χ2[15] = 121.6; P < .0001) and within 2 days of the predicted group; n = 13 per group. B, Discriminant analysis group classification for the pregnant groups only, using the ultrasound measures of SD, AC, and SSF for the predicted group (Wilks λ = 0.451; χ 2[12] = 47.8; P < .0001) and within 2 days of the predicted group; n = 13 per group. D indicates day of pregnancy; and PD, predicted day of gestation.