title: Multiple birth prevalence in The Netherlands. Impact of maternal age and assisted reproductive techniques.
abstract: OBJECTIVE
  To evaluate the impact of maternal age and use of fertility drugs on multiple birth prevalence from 1970 to 1995 in the Netherlands.
  
  
  METHODS
  A population-based survey was carried out in which data were collected from the Centraal Bureau voor Statistiek, the Institute of Medical Statistics and from all clinics for in vitro fertilization.
  
  
  RESULTS
  In the last two decades, the prevalence of multiple births, especially of twin and triplet births, has increased significantly. Three possible explanations for this phenomenon are: (1) introduction of assisted reproductive techniques in combination with fertility drugs; (2) increasing maternal age; and (3) decreasing fecundity with increasing maternal age, resulting in more fertility treatments. A surplus of 1,366 twins was born in 1995 as compared to 1975. The expected excess of twins was 1,368, of which 104 (7.6%) were a result of the increase in total births in 1995, 583 (42.6%) were due to maternal age > 29 years, and, respectively, 330 (24.1%) and 351 (25.7%) twins were due to in vitro fertilization treatment and intrauterine insemination.
  
  
  CONCLUSIONS
  The delay in achieving pregnancy and the use of fertility-promoting therapies profoundly affect the prevalence of multiple pregnancies in a given country. The general population should be informed of this risk.
authors.affiliation: Department of Gynecology, University Hospital Nijmegen, The Netherlands.
authors.forename: R P
authors.initials: RP
authors.lastname: Steegers-Theunissen
authors.forename: W M
authors.initials: WM
authors.lastname: Zwertbroek
authors.forename: A J
authors.initials: AJ
authors.lastname: Huisjes
authors.forename: H H
authors.initials: HH
authors.lastname: Kanhai
authors.forename: H W
authors.initials: HW
authors.lastname: Bruinse
authors.forename: H M
authors.initials: HM
authors.lastname: Merkus
mesh_terms: D000328:Adult; D005260:Female; D005299:Fertility Agents / Q000627:therapeutic use*; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data*; D015995:Prevalence; D018570:Risk Assessment
chemical_list: D005299:Fertility Agents