[Special weight percentile curves for twins]

Based on the birthweights of our data collection on 562 twins between 1970 and 1984 at the Universitäts-Frauenklinik Basle, we have worked out a special percentile curve for twins. Presented are the 10, 50 and 90-percentile curve for boys and girls. The data were calculated with 95% confidence-limits and the curves were equalized by computer. The new curves have the same form as those for single infants, but are shifted down by about 500 g. This can be explained by an intra-uterine growth-retardation, normally with twins, caused by lack of space confirms the necessity of separate percentile curves for twins.