Gestational age assessment in Japanese low birthweight infants.

We evaluated the validity of the Ballard scoring system for assessing gestational age in Japanese low birthweight infants. Infants included in this study were 116 neonates who were admitted to seven hospitals in Hokkaido. Gestational ages of all infants were prenatally established by ultrasonographic measurement of the crown-rump length performed between 8 and 12 weeks of gestation (clinical age). Of these, 74 infants were appropriate for gestational age (AGA) and the remaining were small for gestational age (SGA). Mean birthweight was 1703 g and 34% (39/116) were < 1500 g. The correlation coefficient for the total population was 0.93 (P < 0.001). Although mean Ballard age tended to overestimate clinical age, mean differences between Ballard age and clinical age did not exceed 0.6 weeks. Agreement within 2 weeks among all infants was 86.2%. Percentages of agreement within 2 weeks did not differ to a statistically significant degree between AGA and SGA. These results indicate that the Ballard method is of value in assessing gestational age in Japanese low birthweight infants.