title: Pre-eclampsia and assisted reproductive technologies: consequences of advanced maternal age, interbirth intervals, new partner and smoking habits.
abstract: OBJECTIVE
  To examine the risk of pre-eclampsia (PE) in women conceiving after assisted reproductive technologies (ART). Potential confounding from maternal age, long intervals between births, new partner and smoking were evaluated.
  
  
  METHODS
  Population-based cohort study with data from the Medical Birth Registry of Norway.
  
  
  METHODS
  A total of 501,766 mothers with offspring from 1988 to 2009.
  
  
  METHODS
  Births to the same mother were linked in sibship data files with information of ART.
  
  
  METHODS
  Odds ratio (OR) (95% confidence intervals) of PE in pregnancies conceived by ART compared with spontaneous conception, stratified by parity.
  
  
  RESULTS
  The prevalence of PE was 5.1% in first, 2.2% in second and 2.1% in third pregnancies. Corresponding figures in ART pregnancies were 6.0%, 3.3% and 4.4%. Hence, the odds ratios of PE in ART pregnancies relative to spontaneous pregnancies increased from 1.2 (1.1-1.3) in first, 1.5 (1.3-1.8) in second to 2.1 (1.4-3.3) in third pregnancies. Adjusting by maternal age lowered the odds ratio to 1.3 (1.1-1.6) and 1.8 (1.2-2.8) in second and third pregnancies, respectively. Multi-adjusted, birth interval had more impact than change of partner. Smoking was associated with a strongly reduced PE risk (odds ratio 0.65; 0.62-0.69), but there was no confounding by smoking on the ART associated risk.
  
  
  CONCLUSIONS
  Assisted reproductive technologies increases the risk of PE, and the risk may increase by parity. The association between ART pregnancies and PE is to some extent explained by interbirth intervals and advanced maternal age, but not to change of partner or smoking.
authors.affiliation: Department of Gynaecology and Obstetrics, Haukeland University Hospital, Bergen, Norway.|Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.
authors.forename: A
authors.initials: A
authors.lastname: Tandberg
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.|Medical Birth Registry of Norway, Norwegian Institute of Public Health, Bergen, Norway.
authors.forename: K
authors.initials: K
authors.lastname: Klungsøyr
authors.affiliation: Department of Obstetrics and Gynaecology, Fertility Clinic, St Olav's University Hospital, Trondheim, Norway.|Department of Public Health, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: L B
authors.initials: LB
authors.lastname: Romundstad
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.|Medical Birth Registry of Norway, Norwegian Institute of Public Health, Bergen, Norway.
authors.forename: R
authors.initials: R
authors.lastname: Skjærven
mesh_terms: D000328:Adult; D001721:Birth Intervals / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008423:Maternal Age; D009664:Norway / Q000453:epidemiology; D010298:Parity; D011225:Pre-Eclampsia / Q000453:epidemiology*; D011247:Pregnancy; D015995:Prevalence; D011446:Prospective Studies; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects / Q000706:statistics & numerical data*; D012307:Risk Factors; D012747:Sexual Partners; D012907:Smoking / Q000453:epidemiology*; D055815:Young Adult
keywords: Assisted reproductive technologies; interbirth interval; maternal age; parity; pre-eclampsia; smoking