妇女怀孕后,子宫内不止一个胎儿,而是“双胞胎”、“三胞胎”甚至更多者,称为多胎妊娠。多胎妊娠有单卵性多胞胎和多卵性多胞胎之分,前者是由一个受精卵在囊胚期分裂成两个以上的细胞群,并逐渐发育成两个以上的胎儿;后者则是由两个以上的卵细胞分别与精子结合成两个以上的受精卵,并分别在子宫内着床 When a woman is pregnant, there is more than one fetus in the uterus, but rather “twin,” “triplet,” or even more, a multiple pregnancy. Multiple pregnancy with single egg polygamy and multiple egg multiple births, the former by a fertilized egg in the blastocyst stage split into more than two cell populations, and gradually developed into more than two fetuses; the latter It is more than two oocytes and sperm were combined into more than two fertilized eggs, respectively, and implantation in the womb