![Maternal serum α-fetoprotein, β-human chorionic gonadotropin, and unconjugated estriol levels in midtrimester trisomy 18 pregnancies]()
Maternal serum α-fetoprotein, β-human chorionic gonadotropin, and unconjugated estriol levels in midtrimester trisomy 18 pregnanciesGreenberg, Frank; Schmidt, Deborah; Darnule, Asha T.; Weyland, Barbara R.; Rose, Esmie; Alpert, Elliot · American Journal of Obstetrics and Gynecology · 1992