['Because aortic dilation increases the risk for dissection in the general adult population, and dissection occurs with greater frequency at a young age with Turner syndrome, we studied the prevalence, magnitude, and determinants of aortic dilation in a large group of girls and young women with Turner syndrome.', 'Participants at annual Turner syndrome society meetings completed a questionnaire regarding their medical history. Echocardiographic measurements of their aorta were converted to z scores by using data from a larger group of normal control female subjects. Bivariable and multivariable analyses evaluated the effects of Turner syndrome features, such as a bicuspid aortic valve, coarctation, growth-hormone therapy, blood pressure, and karyotype, on aortic size.', 'Among 138 individuals with Turner syndrome <18 years old, 49% had the 45,X karyotype, 26% had bicuspid aortic valve, 17% had a history of coarctation, 78% had a history of growth-hormone therapy, and 40% had hypertension. Aortic z scores were calculated by using data from 407 control subjects. Bivariable analyses revealed that a bicuspid aortic valve, growth hormone, and 45,X karyotype predicted a larger proximal aorta at >/=1 level. Multivariable analysis predicted a larger proximal aorta at all of the levels only for bicuspid aortic valve individuals and at the annular level for those who received growth hormone. Importantly, all of the analyses revealed that Turner syndrome predicted a larger proximal aorta independent of these characteristics.'] Is turner syndrome an independent risk factor for aortic dilation in the young?