title: Pregnancy risk increases from 41 weeks of gestation.
abstract: BACKGROUND
  The aim of this study was to evaluate the mortality and morbidity of conservatively managed post-term pregnancies (gestation 294 days and beyond).
  
  
  METHODS
  This is a population-based prospective study. The sample was comprised of all women (N=17,493) with a singleton pregnancy in one Norwegian county from 1989 to 1999, with a second-trimester ultrasound examination and delivery after 37 completed gestational weeks.
  
  
  RESULTS
  One thousand three hundred and thirty-six (7.6%) of the deliveries were post-term. In this group, the increase in perinatal mortality reached borderline significance [relative risk (RR) 2.0; 95% confidence interval 0.9-4.6]. Perinatal morbidity expressed as Apgar score <7 at 5 min (RR 2.0; 95% confidence interval 1.2-3.3), and transferal to neonatal intensive care unit (RR 1.6; 95% confidence interval 1.3-2.0) were significantly more frequent. However, RR for perinatal death calculated per 1000 ongoing pregnancies increased significantly from 0.2 in week 37-3.7 in week 42, using perinatal mortality in gestational week 41 as a reference.
  
  
  CONCLUSIONS
  Our results indicate that expectant management of post-term pregnancies allowing pregnancies to continue up to week 43 carries a risk for perinatal mortality and morbidity. The risk increases already from gestational week 41. The guidelines for management of post-term pregnancies should be revised.
authors.affiliation: Department of Obstetrics and Gynecology, Oppland Central Hospital, Lillehammer, Norway. jnakling@online.no
authors.forename: Jakob
authors.initials: J
authors.lastname: Nakling
authors.forename: Bjørn
authors.initials: B
authors.lastname: Backe
mesh_terms: D001034:Apgar Score; D005260:Female; D005313:Fetal Death / Q000453:epidemiology*; D005865:Gestational Age; D006801:Humans; D009664:Norway; D011247:Pregnancy; D011256:Pregnancy Outcome; D018566:Pregnancy, High-Risk; D011273:Pregnancy, Prolonged / Q000401:mortality; D011446:Prospective Studies; D012307:Risk Factors