Changes of the neonatal head diameter during the first week of life.

Significant but slight decreases in the biparietal and bitemporal diameter were observed during the first week of life with different ultrasonic methods. The lowest value was reached after two days. Between two and six days a small increase was observed in the biparietal diameter, corresponding well with the rate of growth reported for the foetal head during the last weeks of pregnancy. Reasons for these changes cannot be clarified on the basis of the present study.