2. Mathews TJ, Hamilton BE. First births to older women continue to rise. National Center for Health Statistics. NCHS Data Brief No. 152. May 2014. http://www.cdc.gov/nchs/data/databriefs/db152.pdf. Accessed October 3, 2014.
3. Cleary-Goldman J, Malone FD, Vidaver J, Ball RH, Nyberg DA, Comstock CH, Saade GR, Eddleman KA, Klugman S, Dugoff L, Timor-Tritsch IE, Craigo SD, Carr SR, Wolfe HM, Bianchi DW, D'Alton M; FASTER Consortium. Impact of maternal age on obstetric outcome. Obstet Gynecol. 2005 May; 105(5 Pt 1): 983-90.
4. Plaza.umin.ac.jp/̃jsog-art/20121017data3.pdf
5. Meyers C, Adam R, Dungan J, Prenger V. Aneuploidy in twin gestations: when is maternal age advanced? Obstet Gynecol. 1997 Feb; 89(2): 248-51.