Layde P M, Erickson J D, Falek A, McCarthy B J
Am J Hum Genet. 1980 Jan;32(1):69-78.
Data from the population-based Metropolitan Atlanta Congenital Defects Program (MACDP) show that the overall rate of malformed infants, as well as the incidence of several specific defects, is higher for twins than for singletons. This elevated risk appears limited to same sex twins and, hence, is probably related to monozygosity. In addition to an 18-fold increase in risk of fetal death compared to singletons, twins have almost a 50% greater likelihood of congenital malformation.
来自基于人群的亚特兰大大都会先天性缺陷项目（MACDP）的数据显示，畸形婴儿的总体发生率以及几种特定缺陷的发生率，双胞胎高于单胎。这种风险升高似乎仅限于同性双胞胎，因此，可能与单合子性有关。与单胎相比，双胞胎除了胎儿死亡风险增加18倍外，先天性畸形的可能性几乎高出50%。
