title: Trends in the occurrence, determinants, and consequences of multiple births.
abstract: After a substantial decrease in the middle of the 20th century, multiple pregnancy rates have increased in many Western countries. Between the mid-1970s and 1998, the rate of twin pregnancies increased by 50% to 60% in England and Wales, France, and the United States. The rates of triplet or higher-order multiple pregnancies increased by 310% in France, 430% in England and Wales, and 696% in the United States. One fourth to one third of the increase in twin or triplet pregnancies are attributable to a contemporaneous increase in maternal age. Furthermore, in countries with high occurrence of multiple births, 30% to 50% of twin pregnancies and at least 75% of triplet pregnancies occur after infertility treatment. The impact of the increase in multiple births on preterm delivery rates in the overall population is mainly attributable to twin pregnancies. In Canada, France, and the United States, an increase in preterm births among multiples contributed almost as much as the increase in occurrence of multiple births to the increase or stabilization of the overall rates of preterm delivery observed in these countries.
authors.affiliation: Epidemiological Research Unit on Perinatal and Women's Health, Institut National de la Santé et de la Recherche Médicale (INSERM), Villejuif, France.
authors.forename: Béatrice
authors.initials: B
authors.lastname: Blondel
authors.forename: Monique
authors.initials: M
authors.lastname: Kaminski
mesh_terms: D000328:Adult; D002170:Canada / Q000453:epidemiology; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007230:Infant, Low Birth Weight / Q000502:physiology; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology; D008423:Maternal Age; D007752:Obstetric Labor, Premature; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology; D011272:Pregnancy, Multiple / Q000502:physiology / Q000706:statistics & numerical data*; D015995:Prevalence; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects / Q000639:trends; D014310:Triplets / Q000706:statistics & numerical data*; D014427:Twins / Q000706:statistics & numerical data*; D006113:United Kingdom / Q000453:epidemiology; D014481:United States / Q000453:epidemiology