Gynecology & Obstetrics
Open Access

Kazuo Hayakawa

Publications

• Research Article
  Annual Trend in Zygotic Twinning Rates and their Association with Maternal Age in Japan, 1999-2008
  Author(s): Yoko Imaizumi and Kazuo HayakawaYoko Imaizumi and Kazuo Hayakawa
  
  Objective: We aimed to determine the recent trend in monozygotic (MZ) and dizygotic (DZ) twinning rates and their association with maternal age (MA). Study design: The MZ and DZ twinning rates were estimated using Japanese vital statistics from 1999 to 2008. Results: The DZ twinning rate per 1000 deliveries increased from 5.10 in 1999 to 7.66 in 2005 and decreased thereafter (5.98 in 2008). The MZ twinning rate increased significantly with an increase in MA in 2002, 2003, 2006, and 2008. Both the DZ and overall twinning rates increased significantly with an increase in MA in each year. From 1960- 1967 to 1999-2008, the DZ twinning rates increased 280% for MA 30-34 years, 290% for MA 35-39, and 370% for MA 40 and over. On the contrary, the MZ twinning rates remained nearly constant with MA for both periods. .. View More»
  DOI: 10.4172/2161-0932.1000189

  Abstract PDF

Relevant Topics