Correlation of head circumference and crown-rump length in newborn infants. A potential indicator of congenital maldevelopment.

A study of 305 consecutive neonatal autopsies done by two prosectors showed a high correlation between the head circumference (HC) and crown-rump length (CR). The calculated formula can be stated approximately as HC equals 0.9 CR + 2.5 cm, and the two measurements are for all practical purposes equal in the immediate neonatal period, regardless of race, sex, age and body weight. When the HC was found to be significantly larger than CR, hydrocephalus and certain types of chondrodystrophy were present. When the HC was significantly smaller than CR, there was a higher incidence of congenital heart disease, especially hypoplastic left heart syndrome, and congenital central nervous system disorders other than hydrocephalus. From a practical point of view, a significant difference is a discrepancy of more than 2.5 cm. 102 consecutive living neonates were also similarly studied. It appears that the CR length when carefully measured under standardized condition is more reliable than the crown-heel length.