title: Mixing nulliparous and multiparous women in randomised controlled trials of preeclampsia prevention is debatable: evidence from a systematic review.
abstract: BACKGROUND
  Nulliparity is a major risk factor of preeclampsia investigated in numerous trials of its prevention.
  
  
  OBJECTIVE
  We aimed to assess whether these trials considered nulliparity in subject selection or analysis of results.
  
  
  METHODS
  01 April 2013 search of MEDLINE via PubMed, EMBASE and the Cochrane Library. 01 April 2013 search of trials registered in Clinicaltrials.gov.
  
  
  METHODS
  Randomised controlled trials and metaanalyses of preeclampsia prevention with no restriction to period of publication or language. Metaanalyses were selected to fully identify relevant trials.
  
  
  METHODS
  One reader appraised each selected article/registered protocol using a pretested, standardized data abstraction form developed in a pilot test. For each article, he recorded whether both nulliparous and multiparous were included and, in case of mixed populations, whether randomisation was stratified, and whether subgroup analyses had been reported. For registered protocols, he only assessed whether it was planned to include mixed populations.
  
  
  RESULTS
  88 randomised controlled trials were identified, representing 83,396 included women. In 58 of the 88 articles identified (65.9%), preeclampsia was the primary outcome. In 31 of these (53.4%), the investigation combined nulliparous and multiparous women; only two reports in 31 (6.5%) stated that randomisation was stratified on parity and only four (12.9%) described a subgroup analysis by parity. Of the 30 registered trials, 20 (66.6%) planned to include both nulliparous and multiparous women.
  
  
  CONCLUSIONS
  Parity is largely ignored in randomised controlled trials of preeclampsia prevention, which raises difficulties in interpreting the results.
authors.affiliation: INSERM, UMR-S 738, Paris, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Simon
authors.forename: Agnès
authors.initials: A
authors.lastname: Caille
authors.forename: Franck
authors.initials: F
authors.lastname: Perrotin
authors.forename: Bruno
authors.initials: B
authors.lastname: Giraudeau
mesh_terms: D005260:Female; D006801:Humans; D010298:Parity; D011225:Pre-Eclampsia / Q000517:prevention & control*; D011247:Pregnancy; D016032:Randomized Controlled Trials as Topic