-
Gestational sac volume measured by three-dimensional ultrasound at 11 to 13 + 6 weeks of gestation: relation to chromosomal defects.
Falcon O, Wegrzyn P, Faro C, Peralta CF, Nicolaides KH.
Ultrasound Obstet Gynecol 2005;25:546-50. -
The 11-14 week scan.
Nicolaides KH, Heath V, Liao AW.
Baillieres Best Pract Res Clin Obstet Gynaecol 2000;14:581-94.