title: Hyperemesis gravidarum and birth outcomes-a population-based cohort study of 2.2 million births in the Norwegian Birth Registry.
abstract: OBJECTIVE
  To study associations between hyperemesis gravidarum (HG) and birth outcomes.
  
  
  METHODS
  Population-based cohort study.
  
  
  METHODS
  Norway.
  
  
  METHODS
  Singleton births in the Norwegian Birth Registry, 1967-2009 (n = 2 270 363).
  
  
  METHODS
  Multiple logistic regression was applied to study associations between HG and dichotomous outcomes; multiple linear regression to study associations between HG, birthweight and gestational length. Generalised estimating equations were applied to obtain valid standard errors. Sub-analysis on data with available information on smoking was conducted (1999-2009).
  
  
  METHODS
  Small and large for gestational age (SGA/LGA), Apgar score after 5 minutes, very preterm and preterm birth (VPTB/PTB), perinatal death, stillbirth, neonatal death, birthweight and gestational length.
  
  
  RESULTS
  No associations between HG and adverse pregnancy outcomes were observed in crude analyses, except for VPTB (odds ratio [OR] 0.79, 95% CI 0.67-0.93). In adjusted analysis, HG was associated with perinatal death (OR 1.27, 95% CI 1.08-1.48). Inverse associations were observed between HG and VPTB (OR 0.80, 95% CI 0.68-0.94) and LGA (OR 0.95, 95% CI 0.90-0.99). Sub-analyses showed no associations between HG and perinatal death (OR 1.29, 95% CI 0.91-1.83). The inverse associations between HG, VPTB and LGA were strengthened (OR 0.66, 95% CI, 0.48-0.91 and OR 0.86, 95% CI 0.79-0.93, respectively). Exposed babies had reduced birthweight and gestational length compared with unexposed, adjusted difference - 21.4 g and - 0.5 days, respectively. Adjustment for smoking slightly strengthened the impact of HG on birthweight.
  
  
  CONCLUSIONS
  Inverse associations for HG and VPTB and LGA were observed. HG was associated with slight reductions in birthweight and gestational age.
authors.affiliation: Department of Genes and Environment, Division for Epidemiology, Norwegian Institute of Public Health, Oslo, Norway; Norwegian Resource Centre for Women's Health, Rikshospitalet, Oslo, Norway.
authors.forename: K F
authors.initials: KF
authors.lastname: Vandraas
authors.forename: A V
authors.initials: AV
authors.lastname: Vikanes
authors.forename: S
authors.initials: S
authors.lastname: Vangen
authors.forename: P
authors.initials: P
authors.lastname: Magnus
authors.forename: N C
authors.initials: NC
authors.lastname: Støer
authors.forename: A M
authors.initials: AM
authors.lastname: Grjibovski
mesh_terms: D000328:Adult; D001724:Birth Weight; D015331:Cohort Studies; D005260:Female; D047109:Fetal Development; D006801:Humans; D006939:Hyperemesis Gravidarum / Q000453:epidemiology*; D007231:Infant, Newborn; D015999:Multivariate Analysis; D009664:Norway / Q000453:epidemiology; D054238:Perinatal Mortality; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D012042:Registries; D055815:Young Adult
keywords: birth outcomes; hyperemesis; registry