Table 3

Agreement between early ultrasound dating versus gestational age (GA) determined by last menstrual period (LMP), Ballard Score and AMANHI machine learning models (A, B, C, D)

GA determined by:NMean difference in days (95% CI) (GA test method—GA ultrasound)Bland-Altman 95% limits of agreement (in days)Precision of predicted GA (in days)*
LMP† (<37 weeks)7428−1.69 (−2.15 to –1.24)(−41.0 to 37.6)±39.3
Original Ballard Score‡74289.16 (8.87 to 9.44)(−15.3 to 33.6)±24.5
AMANHI model A
Newborn 10-characteristics § (including birth weight)
74280.03 (−0.17 to 0.23)(−17.3 to 17.4)±17.3
AMANHI model B
Newborn 10-characteristics§+LMP†
74280.03 (−0.15 to 0.22)(−15.7 to 15.8)±15.7
AMANHI model C
Birth weight+LMP†
74280.07 (−0.13 to 0.26)(−16.6 to 16.8)±16.7
AMANHI model D
Birth weight+head circumference
74280.06 (−0.15 to 0.28)(−18.3 to 18.4)±18.4
  • *Interpretation: Refers to the precision of the predicted GA values estimated by the test method bias (95% CI of the individual differences) around the mean difference.

  • †LMP: In this study LMP was collected from maternal recall at <20 weeks gestation in all sites as part of prospective research studies.

  • ‡Ballard Score: GA was calculated from the Ballard signs as described in Ballard et al29 using the formula GA=((2×score)+120))/5.

  • §AMANHI 10-characteristics: Birth weight, head circumference, chest circumference, foot length, breast bud diameter, breast development, foot surface (plantar creases), skin texture, ankle dorsiflexion, infant sex.

  • AMANHI, Alliance for Maternal and Newborn Health Improvement.