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Frontomaxillary and mandibulomaxillary facial angles at 11 + 0 to 13 + 6 weeks in fetuses with trisomy 18.
Borenstein M, Persico N, Strobl I, Sonek J, Nicolaides KH.
Ultrasound Obstet Gynecol 2007;30:928-33. -
Maternal serum activin A and inhibin A in trisomy 18 pregnancies at 10-14 weeks.
Spencer K, Liao AW, Ong CY, Flack NJ, Nicolaides KH.
Prenat Diagn 2001;21:571-4.