Growth standards for twins from birth to four years

SummaryGrowth standards for twins are presented for weight, height, and head circumference, based on a sample repeatedly measured from birth to four years of age. The results give the means, SDs, and selected centiles for the size attained at each age, the amount of gain between ages, and the size differences within twin pairs. Sex differences in growth rate were evident at several ages; males grew more rapidly during the first 6 months, whereas females grew more rapidly during the third year. Comparing high and low birth-weight twins, the mean weight gain was the same for both groups during the first two years, and the weight differential remained constant also, but there was an increasing degree of overlap between the two weight distributions. By age 4, over 20% of the low birth-weight twins were larger than the average high birth-weight twins.Compared to singletons, the twins' size deficit was greatest at birth but there was a marked recovery in the first six months, followed by only gradual changes thereafter. Weight was somewhat more affected by growth suppression than height; the twins remained 0·45 SD below the singletons for weight through age 4, whereas they nearly achieved parity for height. The results suggest that prenatal adipose-cell replication may be restricted by the nutritional demands of a twin pregnancy.