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Title
Re: First-trimester combined screening for trisomy 21 with different combinations of placental growth factor, free β-human chorionic gonadotropin and pregnancy-associated plasma protein-A.
A letter to the editor is presented in response to the article "First-trimester combined screening for trisomy 21 with different combinations of placental growth factor, free B-human chorionic gonadotropin and pregnancy-associated plasma protein-A" in the 2012 issue.