Predicting head circumference at birth: a study in a Dutch population using the Rossavik growth model

The use of the Rossavik growth model for predicting neonatal head circumference from data obtained from two ultrasound scans before 28 weeks' menstrual age was investigated in 50 pregnant women with singleton pregnancy in a Dutch population. The head circumference predicted at 38, 39, 39.5 and 40 weeks' gestation and at birth was compared to the head circumference observed at birth. The accuracy was expressed in percentage difference and the growth potential realization index (GPRIHC) was used as an indicator of growth outcome. The predictions at 39.5 weeks and 40 weeks were accurate without systematic error. Prediction at 38 weeks showed a statistical underprediction (mean +/- SD = -2.3 +/- 2.0%, p < 0.05) and at birth a systematic overprediction (mean +/- SD = +1.4 +/- 2.1%, p < 0.05). Based on the regression analyses of percentage differences against birth ages, the growth of the head circumference appeared to stop at about 39.5 weeks. The results of the present study were compared to studies of populations in the United States. The growth of the head circumference before 28 weeks was similar in all samples studied, but growth cessation was at 38 weeks in the fetuses in the USA and at 39.5 weeks in these Dutch fetuses. The mean values of GPRIHC were not different from 100% in all samples studied and the ranges were similar (mean, 100.3%; range, 97-103% in the present study).