title: A prospective study of twinning and perinatal mortality in urban Guinea-Bissau.
abstract: BACKGROUND
  Despite twinning being common in Africa, few prospective twin studies have been conducted. We studied twinning rate, perinatal mortality and the clinical characteristics of newborn twins in urban Guinea-Bissau.
  
  
  METHODS
  The study was conducted at the Bandim Health Project (BHP), a health and demographic surveillance site in Bissau, the capital of Guinea-Bissau. The cohort included all newborn twins delivered at the National Hospital Simão Mendes and in the BHP study area during the period September 2009 to August 2011 as well as singleton controls from the BHP study area. Data regarding obstetric history and pregnancy were collected at the hospital. Live children were examined clinically. For a subset of twin pairs zygosity was established by using genetic markers.
  
  
  RESULTS
  Out of the 5262 births from mothers included in the BHP study area, 94 were twin births, i.e. a community twinning rate of 18/1000. The monozygotic rate was 3.4/1000. Perinatal mortality among twins vs. singletons was 218/1000 vs. 80/1000 (RR = 2.71, 95% CI: 1.93-3.80). Among the 13783 hospital births 388 were twin births (28/1000). The hospital perinatal twin mortality was 237/1000.Birth weight < 2000g (RR = 4.24, CI: 2.39-7.51) and caesarean section (RR = 1.78, CI: 1.06-2.99) were significant risk factors for perinatal twin mortality. Male sex (RR = 1.38, CI: 0.97-1.96), unawareness of twin pregnancy (RR = 1.64, CI: 0.97-2.78) and high blood pressure during pregnancy (RR = 1.77, CI: 0.88-3.57) were borderline non-significant. Sixty-five percent (245/375) of the mothers who delivered at the hospital were unaware of their twin pregnancy.
  
  
  CONCLUSIONS
  Twins had a very high perinatal mortality, three-fold higher than singletons. A birth weight < 2000g was the strongest risk factor for perinatal death, and unrecognized twin pregnancy was common. Urgent interventions are needed to lower perinatal twin mortality in Guinea-Bissau.
authors.affiliation: Bandim Health Project, INDEPTH Network, Apartado 861, 1004, Bissau Codex, Guinea-Bissau. mban@dadlnet.dk
authors.forename: Morten
authors.initials: M
authors.lastname: Bjerregaard-Andersen
authors.forename: Najaaraq
authors.initials: N
authors.lastname: Lund
authors.forename: Frida Staarup
authors.initials: FS
authors.lastname: Jepsen
authors.forename: Luis
authors.initials: L
authors.lastname: Camala
authors.forename: Margarida Alfredo
authors.initials: MA
authors.lastname: Gomes
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.forename: Lene
authors.initials: L
authors.lastname: Christiansen
authors.forename: Dorte Møller
authors.initials: DM
authors.lastname: Jensen
authors.forename: Peter
authors.initials: P
authors.lastname: Aaby
authors.forename: Henning
authors.initials: H
authors.lastname: Beck-Nielsen
authors.forename: Christine Stabell
authors.initials: CS
authors.lastname: Benn
authors.forename: Morten
authors.initials: M
authors.lastname: Sodemann
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002585:Cesarean Section / Q000706:statistics & numerical data; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D006169:Guinea-Bissau; D015658:HIV Infections / Q000453:epidemiology*; D006801:Humans; D046110:Hypertension, Pregnancy-Induced / Q000453:epidemiology*; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008297:Male; D054238:Perinatal Mortality; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology*; D059285:Pregnancy, Twin / Q000706:statistics & numerical data*; D011446:Prospective Studies; D012307:Risk Factors; D012737:Sex Factors; D014429:Twins, Dizygotic / Q000706:statistics & numerical data*; D014430:Twins, Monozygotic / Q000706:statistics & numerical data*; D014505:Urban Population / Q000706:statistics & numerical data; D055815:Young Adult