title: Routine ultrasound examination at 41 weeks of gestation and risk of post-term severe adverse fetal outcome: a retrospective evaluation of two units, within the same hospital, with different guidelines.
abstract: OBJECTIVE
  To study whether a routine with a routine ultrasound examination (routine scan) at 41 gestational weeks as compared with ultrasound on clinical indication (indicated scan), lowered the risk of severe adverse fetal outcome in post-term period.
  
  
  METHODS
  A retrospective cohort study.
  
  
  METHODS
  Karolinska University Hospital, Stockholm, Sweden.
  
  
  METHODS
  Eight years of deliveries, 2002-2009.
  
  
  METHODS
  One of the two delivery units at Karolinska University Hospital used a routine scan at 41 week of gestation and the other unit used an indicated scan. Severe adverse fetal outcome were defined: severe asphyxia, death or cerebral damage. The study was analysed using logistic regression with adjustment for potential confounders.
  
  
  METHODS
  Differences in post-term severe adverse fetal outcome.
  
  
  RESULTS
  No increased risk of post-term severe adverse fetal outcome was seen at the unit using a routine scan; conversely, a 48% significantly increased risk was seen at the unit using an indicated scan (OR 0.89, 95% confidence interval, CI, 0.5-1.5 and OR 1.48, 95% CI 1.06-2.1, respectively). Comparing post-term periods, there was no significantly increased risk at the unit using indicated scans (OR 1.6, 95% CI 0.9-3.0). There was a 60% increased prevalence of small-for-gestational age (SGA) newborns in the post-term period at the unit using indicated scans (OR 1.6, 95% CI 1.1-2.4), but no differences in operative delivery.
  
  
  CONCLUSIONS
  A policy to use routine scans at 41 weeks of gestation seems to normalise an increased post-term risk of severe adverse fetal outcome, possible due to increased awareness of SGA and/or oligohydramniosis.
authors.affiliation: Department of Obstetrics and Gynaecology, Clintec, Karolinska Institute, Karolinska University Hospital, Huddinge, Stockholm, Sweden.
authors.forename: P G
authors.initials: PG
authors.lastname: Lindqvist
authors.forename: K
authors.initials: K
authors.lastname: Pettersson
authors.forename: A
authors.initials: A
authors.lastname: Morén
authors.forename: M
authors.initials: M
authors.lastname: Kublickas
authors.forename: L
authors.initials: L
authors.lastname: Nordström
mesh_terms: D000328:Adult; D001238:Asphyxia Neonatorum / Q000453:epidemiology* / Q000517:prevention & control; D001927:Brain Diseases / Q000453:epidemiology* / Q000517:prevention & control; D003955:Diagnostic Tests, Routine / Q000009:adverse effects*; D005260:Female; D005313:Fetal Death / Q000453:epidemiology* / Q000517:prevention & control; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D017410:Practice Guidelines as Topic; D011247:Pregnancy; D011256:Pregnancy Outcome; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D016216:Ultrasonography, Prenatal / Q000009:adverse effects*
keywords: Adverse outcome; asphyxia; death; intra-uterine growth restriction; post-term; prediction; screening; ultrasound