[Distance and velocity standards for head circimference growth before and after term until 18 months--results from a longitudinal study (author's transl)].

Standards for head circumference growth (distance and velocity) from the perinatal period until the age of 18 months have been based on repeated measurements at short intervals (longitudinal) in 60 appropriate for gestational age (AGA) preterm infants of very low fetal age, and 68 full term infants. Moreover the growth of 32 small for gestational age (SGA) preterm infants has been evaluated. Before term the extrauterine head growth curve is similar to that of "intrauterine curves". At term and until the age of 18 months the growth curves of AGA preterm infants agree well with those of the full term controls, without statistically significant differences (p greater than 0.1). If the age is not corrected for prematurity ther is a significant difference between preterm and full term infants until 17 months (p less than 0.05). With decreasing velocity of head circumference growth this difference becomes non-significant at the age of 18 months (p greater than 0.1). Out of the heterogenious group of 32 SGA preterm infants 15 have shown a catch-up growth in head circumference until the third month, whereas 17 infants remained significantly below the growth curve of the AGA. Growth velocity of head circumference, calculated in cm/month, in the last 10 weeks before term is significantly higher (p less 0.025) than later on, with a mean peak of 4.3 cm in the 34th postmentstrual week. After term, the velocity curve of the AGA preterm infants agrees with that of the full term controls. A period of rapid head circumference growth -- a growth spurt -- extends from the 31st postmenstrual week until the 6th month after term. In the following months the velocity curves flatten. If the age is not corrected for prematurity, the peak of the velocity curve becomes flat and spread with a mean growth velocity of 3.0 cm in the first, of 3.4 cm in the second and of 2.5 cm in the third month.