Monteagudo A
Department of Obstetrics & Gynecology, NYU Medical Center, 550 First Avenue Room 9N28, New York, NY 10016, USA.
Croat Med J. 1998 Jun;39(2):191-6.
During the first trimester, chorionicity can be assessed as early as five weeks post-conception, but a reliable detection of amnionicity cannot be performed before the 8th week when the amnion can be clearly imaged. The late second and third trimesters twin pregnancies are a true challenge to the imaging specialist because the detection of chorionicity and amnionicity has to rely upon sonographic clues, such as placenta location, fetal gender, membrane origin, thickness, and layer. Sonographic methods used to determine chorionicity and amnionicity in twins can be extrapolated to any multifetal pregnancy, regardless of the number of fetuses present.
在孕早期，早在受孕后五周就可以评估绒毛膜性，但在第8周羊膜能够清晰成像之前，无法可靠地检测羊膜性。孕晚期的双胎妊娠对影像专家来说是一项真正的挑战，因为绒毛膜性和羊膜性的检测必须依靠超声线索，如胎盘位置、胎儿性别、胎膜来源、厚度和层次。用于确定双胎妊娠绒毛膜性和羊膜性的超声方法可以外推到任何多胎妊娠，无论胎儿数量多少。
