title: Projections of population-based twinning rates through the year 2100.
abstract: OBJECTIVE
  To present the first compilation of population-based twinning rates published after the year 1990 and to project population-based twinning rates through the year 2100.
  
  
  METHODS
  We searched the Internet-based MEDLINE database for articles published after 1990 in which population-based twinning rates were described. We used population-based data from national statistical authorities from Australia, Austria, Canada, Finland, Hong Kong, Israel, Japan, Norway, Singapore and Sweden, published by Y. Imaizumi in a recent article. U.S. figures were based on data from the National Center for Health Statistics. Annual growth rates of twinning were calculated and graphed, making the assumption that these rates would remain constant throughout the next century.
  
  
  RESULTS
  Our report presents the most recent population-based twinning rates. When projected through the year 2015, twinning rates reach figures that could best be described as derived from a Jules Verne novel: Sweden, in this model, would have four times more twin than singleton births.
  
  
  CONCLUSIONS
  We strongly suggest that physicians reexamine their patterns of prescribing ovulation-inducing agents, which carry a greatly increased risk of multiple pregnancy.
authors.affiliation: Department of Obstetrics and Perinatology, Medical University of Lublin, Poland.
authors.forename: J J
authors.initials: JJ
authors.lastname: Oleszczuk
authors.forename: D M
authors.initials: DM
authors.lastname: Keith
authors.forename: L G
authors.initials: LG
authors.lastname: Keith
authors.forename: W F
authors.initials: WF
authors.lastname: Rayburn
mesh_terms: D000328:Adult; D016208:Databases, Factual; D005260:Female; D005544:Forecasting; D014943:Global Health; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D010062:Ovulation Induction; D011247:Pregnancy; D014427:Twins / Q000706:statistics & numerical data*