6Levene MI, Wild J, Steer P. Higher multiple births and the modern management ofinfertility in Britain. Br J Obstet Gynecol, 1992,99:607-13
7Powers WF, Kiely L. The risks confronting twins: a national perspective. ObstetGynecol, 1994,170:456-61
8Stone J, Lapinlki R, Alvarez M, et al. Are twins＞38 weeks gestation"postdates”? Am J Obstet Gynecol, 1995,172:276
9Kilby MD, Govind A, O'Brien S. Outcomes of twin pregnancies complicated by a singleintrauterine death: a comparison with viable twin pregnancies. Obstet Gynecol,1994,84:107-109
10Clarke JP, Roman JD. A review of 19 sets of triplets: the positive results ofvaginal delivery. Aust NZ J Obstet Gynecol, 1994,34:50-53
