title: [Multiple pregnancies prevalence: its raise on last decade].
abstract: BACKGROUND
  Multiple pregnancies prevalence has been increasing in last decade, which have also increased the requirements of neonatal intensive care units and all problems related to premature neonate or low birth weight. Prevalence rate of twin (18 to 26 in 1,000 births), and triple pregnancies (0.37 to 1.74 in 1,000 births) have raised too, perhaps due to assisted reproductive techniques.
  
  
  OBJECTIVE
  To know incidence of multiple pregnancies at Unidad Medica de Alta Especialidad no. 23, from Institute Mexicano del Seguro Social.
  
  
  METHODS
  Retrospective and descriptive study. We review the files of multiple pregnancies from 1972 to 2006 to estimate its rate and change every five and ten years.
  
  
  RESULTS
  We registered 9,055 twin pregnancies during the period, with a rate of 7.1 to 14.4 in 1,000 (63% of increase in the last decade [12.6 in 1,000 births] compared with the previous decade [7.7 in 1,000 births]; p < 0.005). Pregnancies with three or more fetuses were 202, with 191 triplets, 13 with four, three with five, and one with six products (646 newborns). Incidence of multiple pregnancies with four or more products has also increased in last decade: 230 times higher than two decades before.
  
  
  CONCLUSIONS
  Multiple pregnancies rate has increased in last decade: 63% in twin pregnancies, 217% in triplets, and 230 times more than expected in four or more products pregnancies.
authors.affiliation: Departamento de neonatología, Unidad Médica de Alta Especialidad núm 23, IMSS, Monterrey, Nuevo León, Mexico. richdzher@hotmail.com
authors.forename: Ricardo Jorge Hernández
authors.initials: RJ
authors.lastname: Herrera
authors.forename: Mauro Ochoa
authors.initials: MO
authors.lastname: Torres
authors.forename: Roberto Flores
authors.initials: RF
authors.lastname: Santos
authors.forename: Raúl Cortés
authors.initials: RC
authors.lastname: Flores
authors.forename: Gerardo Forsbasch
authors.initials: GF
authors.lastname: Sánchez
mesh_terms: D005260:Female; D006801:Humans; D015994:Incidence; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data*; D015995:Prevalence; D012189:Retrospective Studies