Figure 2. Model Versus Biometry in the Main Test Set and IVF Test Set.

^a solid line indicates y = x, ^b dashed horizontal lines represent expected error bounds of ultrasound biometry according to the American College of Obstetricians and Gynecologists.⁴ In Zambia, “ground truth” gestational age is defined by the first ultrasound. In North Carolina it is defined by an algorithm incorporating both the last menstrual period and the first ultrasound⁴ (main test set) or by the known fertilization date (IVF test set). GA denotes gestational age and IVF in vitro fertilization.