1. Three decades of twin births in the United States, 1980–2009;JA Martin;NCHS Data Brief,2012
2. ACOG practice bulletin no.144: multifetal gestations: twin, triplet, and higher-order multifetal pregnancies;Obstet Gynecol,2014
3. Trends in multiple births conceived using assisted reproductive technology, United States, 1997–2000;MA Reynolds;Pediatrics,2003
4. NCHS data brief, no 21;TJ Mathews,2009
5. Aneuploidy in twin gestations: when is maternal age advanced?;C Myers;Obstet Gynecol,1997