Swedish Standard Curves for Intra-Uterine Growth

The classification of newborn infants according to intra-uterine growth must take into account gestational age as well as birth weight. Also important is the intrauterine growth pattern of the population from which individual and epidemiological data are derived and to which they are to be compared. In constructing a definition of "normal" intra-uterine growth, the only practical approach now seems to be a statistical definition from data on live born infants of supposedly normal pregnancies. In Sweden it has been possible to collect such information from material compiled primarily for forensic purposes. Because the resultant curves have been published only in Swedish1, and because the birth weight at term in Sweden has been said to be the highest so far obtained2, the curves are presented here for readers from other countries. The Swedish National Board of Health instructed all maternity wards to report certain data on all infants born from July 1, 1956, to June 30, 1957. Due to various reasons, some small hospitals could not take part. After an intense correspondence to complete the reports, the material included 92,348 infants (51.7% boys). It was calculated that about 110,000 infants were born in the whole country during the period in question. Stillborn and malformed infants were excluded, as were those born to mothers with clinical diabetes mellitus and toxemia (proteinuria at two separate occasions and/or resting systolic blood pressure above 150 mm Hg). Only single births were included. The material now contained 82,011 infants (51.0% boys). Before constructing the curves, it was also decided that the normal menstrual pattern of the mothers had to be known and had to be regular with intervals within 21 to 35 days.