1双胎妊娠流行病学、合子性质及绒毛膜性自从20世纪80年代以后,在加拿大和其他发展国家多胎妊娠的发生率大幅度的增加。在1995~2004年期间,多胎妊娠的出生率从2.2%稳定增长到3.0%[1]。主要的2个原因是妇女生育年龄普遍提高、辅助生殖技术的普及与不规范的卵巢刺激。合子性质反映了胎儿的遗传同一性,而绒毛膜性指的是胎盘的分布。在单合子双胎中,单个受精 Epidemiology, zygophilia and chorionicity of twin pregnancies Since the 1980s, the incidence of multiple pregnancies has increased significantly in Canada and other developing countries. Between 1995 and 2004, the birth rate of multiple pregnancies steadily increased from 2.2% to 3.0% [1]. The main two reasons are the general increase of women’s reproductive age, the popularity of assisted reproductive technology and non-standard ovarian stimulation. Zygotic properties reflect the genetic identity of the fetus, and chorionic refers to the distribution of the placenta. In monocentric twins, single fertilization