All | Nulliparous | Parous | |
Ultrasound visit | (n = 353) | (n = 134) | (n = 219) |
Gestational agea | |||
Last menstrual period, days | 76.1 (12.5) | 78.8 (12.8) | 74.4 (12.1) |
Crown-rump length, days | 73.3 (12.9) | 74.6 (12.7) | 72.5 (13.0) |
LMP-CRL, days | 2.8 (10.8) | 4.2 (10.0) | 1.9 (11.2) |
Convergent validityb | |||
Pearson’s correlation coefficient | 0.63 | 0.69 | 0.61 |
Bias Correction Factor | 0.98 | 0.95 | 0.99 |
Lin’s concordance correlation coefficient (95 % CI) | 0.63 (0.56, 0.69) | 0.66 (0.56, 0.75) | 0.60 (0.52, 0.68) |
Live birth | (n = 332) | (n = 127) | (n = 205) |
Gestational agea | |||
Last menstrual period, days | 276.2 (18.1) | 275.9 (17.7) | 276.5 (18.4) |
Crown-rump length, days | 273.4 (14.2) | 271.6 (13.6) | 274.6 (14.5) |
LMP-CRL, days | 2.8 (10.7) | 4.3 (10.0) | 1.9 (11.0) |
Convergent validityb | |||
Pearson’s correlation coefficient | 0.81 | 0.83 | 0.80 |
Bias correction factor | 0.96 | 0.93 | 0.97 |
Lin’s concordance correlation coefficient (95 % CI) | 0.77 (0.73, 0.81) | 0.77 (0.71, 0.83) | 0.77 (0.72, 0.83) |
Validity of classifying preterm | |||
Prevalence of preterm by LMP, % (n) | 10.8 (36) | 13.4 (17) | 9.3 (19) |
Prevalence of preterm by CRL, % (n) | 8.7 (29) | 11.0 (14) | 7.3 (15) |
Sensitivity, % | 86.2 | 92.9 | 80.0 |
Specificity, % | 96.4 | 96.5 | 96.3 |
Positive predictive value, % | 69.4 | 76.5 | 63.1 |
Kappa | 0.74 | 0.82 | 0.68 |
Validity of classifying post-term | |||
Prevalence of post-term by LMP, % (n) | 14.2 (47) | 15.0 (19) | 13.7 (28) |
Prevalence of post-term by CRL, % (n) | 3.6 (12) | 1.6 (2) | 4.9 (10) |
Sensitivity, % | 66.7 | 87.2 | 60.0 |
Specificity, % | 88.8 | 87.4 | 89.7 |
Positive predictive value, % | 18.2 | 11.1 | 23.1 |
Kappa | 0.24 | 0.18 | 0.28 |