title: Recurrence of prolonged pregnancy.
abstract: BACKGROUND
  We conducted a cohort study in an attempt to determine whether prolonged pregnancy in mother is a risk factor for prolonged pregnancy in daughter, and if previous prolonged pregnancy is a risk factor for prolonged pregnancy in subsequent pregnancy.
  
  
  METHODS
  Data from the Swedish Medical Birth Registry were combined with a local registry of births (1955-1990). Mother-daughter pairs (with events of delivery in each generation) were identified. Relative risk (RR) and its 95% confidence interval (CI) were calculated and population attributable proportion was estimated when appropriate.
  
  
  RESULTS
  If mother had had prolonged pregnancy at delivery of daughter the relative risk (RR) of prolonged pregnancy in daughter was moderately raised (RR = 1.3; CI : 1.0-1.7) with population attributable proportions ranging between 2.1% and 4.6%. If previous pregnancy had been prolonged, the RR of prolonged pregnancy at subsequent birth was increased 2-3 fold with population attributable proportions of 12.5% to 15.8%. Possible confounders such as mother's parity, age and maternal age did not alter the risks.
  
  
  CONCLUSIONS
  Although moderate, prolonged pregnancy in mother may be a risk factor for prolonged pregnancy in daughter. A previous prolonged pregnancy increases the risk of prolonged pregnancy in a subsequent birth. However, the familial factor of prolonged pregnancy explains just a minor part of its occurrence in the population (due to small population attributable proportions).
authors.affiliation: Department of Obstetrics and Gynecology, Umeå University, Sweden.
authors.forename: I
authors.initials: I
authors.lastname: Mogren
authors.forename: H
authors.initials: H
authors.lastname: Stenlund
authors.forename: U
authors.initials: U
authors.lastname: Högberg
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D011247:Pregnancy; D011273:Pregnancy, Prolonged / Q000235:genetics; D015995:Prevalence; D012008:Recurrence; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology