The goal of this study is to compare the features of Turner syndrome in girls who are diagnosed before birth because of fetal concerns versus those who are diagnosed when their mother has an amniocentesis for another reason.

This is an observational study which will look at girls who are diagnosed with Turner syndrome before they are born. Girls will be divided into two groups: 1) those diagnosed because of features seen on ultrasound which raised the question of Turner syndrome and 2) those diagnosed incidentally when their mother had an amniocentesis for another reason such as advanced maternal age.

No clinical procedures nor interventions will be done as part of this data collection study which will occur for the first 3 to 6 years of the girl's life. The investigators will be looking to see if girls who are diagnosed incidentally have less features of Turner syndrome than those girls who are diagnosed because of fetal ultrasound.

Inclusion Criteria:

• Turner syndrome diagnosed prenatally
• Less than 4 months of age at time of enrollment

Exclusion Criteria:

• Turner syndrome diagnosed postnatally
• Older than 4 months of age at time of enrollment

Girls who are diagnosed with Turner syndrome prenatally.