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Prefrontal space ratio: comparison between trisomy 21 and euploid fetuses in the second trimester.
Sonek J, Molina F, Hiett AK, Glover M, McKenna D, Nicolaides KH.
Ultrasound Obstet Gynecol 2012;40:293-6. -
Frontomaxillary facial angle in fetuses with spina bifida at 11-13 weeks.
Lachmann R, Picciarelli G, Moratalla J, Green N, Nicolaides KH.
Ultrasound Obstet Gynecol 2010;36:268-71.