Turner's syndrome (TS) is one of the most frequent diseases accompanied by growth deficiency. Though developmental disorders have been observed in the fetal period, there has been disagreement as to whether short stature is frequent in newborn girls with Turner's syndrome. Hence we attempted to determine the incidence of 'small for gestational age' in TS compared with healthy newborns girls delivered at term above -2 SD (body length and weight) for gestational age. The medical records of 548 girls with TS recruited from Polish university and district hospitals were screened, with 468 of them delivered at term (gestational age > or =38 weeks) being included in this study. Mean weight (+/- SD) at birth was 2963 +/- 444 g, which was below the normal value for gestational age in nearly 90%. The mean birth weight deficiency was 600 g, but exceeded 1000 g in over 10%. When a newborn girl delivered at term has a marked weight deficit, Turner's syndrome should be considered. This is especially so when the girl is a product of a first pregnancy, when routine karyotyping is recommended. The condition may arise from a partial dysfunction of a gene or genes on the X-chromosome involved in the control of fetal growth.