Evaluation of perinatal growth. Presentation of combined intra- and extrauterine growth standards for weight, length and head circumference.

The evaluation of perinatal growth requires different approaches depending on the chronological age of the infant. Basically, three periods of perinatal growth are to be distinguished: Intrauterine period: Growth during this period can be estimated by intrauterine growth standards representing fetal growth parameters at birth. Transitional period: Growth during the first 6 to 12 days of life is of transitional nature. It is characterized by large individual variations and does not follow any growth standards. Extrauterine period: After the 6th to 12th day of life growth rates are distinctly higher than those of intrauterine growth. Thus, intrauterine growth standards can not be applied to extrauterine growth, and separate growth standards are required to evaluate growth during this period. In this article combined intra- and extrauterine growth standards for weight, length and head circumference in boys and girls between 28 weeks of gestation and 8 weeks after term are presented. These growth standards are based on the Winterthur Newborn Study (1962-1974) and the Second Zurich Longitudinal Study (1974-1980).