5Kiely TL. What is the population-based risk of preterm birth among twins and other multiples [J].Clin Obstet Gynecol, 1998, 41(4):3.
6Edwin R, Guzman MD, Christine WRDMS, et al. Use of cervical ultrasonography in prediction of spontaneous preterm birth in twin gestations [J].Am J Obstet Gynecol, 2000, 183(5):1103.
7Stan C, Boulvain M, Hirsbrunner-Amagbaly P, et al. Hydration for treatment of preterm labour [EB/OL]. Cochrane Database Syst Rev, 2002(2):CD 003096.
8Sibai B, Hauth J, Cartis S, et al. Hypertensive disorders in twin versus singleton gestations [J]. Am J Obstet Gynecol, 2000, 182(4):938.
9Brabin BJ, Hakimi M, Pelletier D. An analysis of anemia and pregnancy-related maternal mortality [J].J Nutr, 2001, 131(2s-2): 604.
10Reece EA, Hobbins JC. Medicine of the fetus and mother [M]. 2nded. Philadelphia: Lippincott-Raven, 1999, 243.