title: Spontaneous abortion, stillbirth and hyperthyroidism: a danish population-based study.
abstract: OBJECTIVE
  Pregnancy loss in women suffering from hyperthyroidism has been described in case reports, but the risk of pregnancy loss caused by maternal hyperthyroidism in a population is unknown. We aimed to evaluate the association between maternal hyperthyroidism and pregnancy loss in a population-based cohort study.
  
  
  METHODS
  All pregnancies in Denmark from 1997 to 2008 leading to hospital visits (n = 1,062,862) were identified in nationwide registers together with information on maternal hyperthyroidism for up to 2 years after the pregnancy [hospital diagnosis/prescription of antithyroid drug (ATD)]. The Cox proportional hazards model was used to estimate adjusted hazard ratio (aHR) with 95% confidence interval (CI) for spontaneous abortion (gestational age <22 weeks) and stillbirth (≥22 weeks), reference: no maternal thyroid dysfunction.
  
  
  RESULTS
  When maternal hyperthyroidism was diagnosed before/during the pregnancy (n = 5,229), spontaneous abortion occurred more often both in women treated before the pregnancy alone [aHR 1.28 (95% CI 1.18-1.40)] and in women treated with ATD in early pregnancy [1.18 (1.07-1.31)]. When maternal hyperthyroidism was diagnosed and treated for the first time in the 2-year period after the pregnancy (n = 2,361), there was a high risk that the pregnancy under study had terminated with a stillbirth [2.12 (1.30-3.47)].
  
  
  CONCLUSIONS
  Both early (spontaneous abortion) and late (stillbirth) pregnancy loss were more common in women suffering from hyperthyroidism. Inadequately treated hyperthyroidism in early pregnancy may have been involved in spontaneous abortion, and undetected high maternal thyroid hormone levels present in late pregnancy may have attributed to an increased risk of stillbirth.
authors.affiliation: Department of Endocrinology, Aalborg University Hospital, Aarhus, Denmark ; Department of Clinical Medicine, Aalborg University, Aalborg, Aarhus, Denmark.
authors.forename: Stine Linding
authors.initials: SL
authors.lastname: Andersen
authors.affiliation: Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark.
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
authors.affiliation: Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark.
authors.forename: Chun Sen
authors.initials: CS
authors.lastname: Wu
authors.affiliation: Department of Endocrinology, Aalborg University Hospital, Aarhus, Denmark ; Department of Clinical Medicine, Aalborg University, Aalborg, Aarhus, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Laurberg
keywords: Antithyroid drug; Graves' disease; Hyperthyroidism; Pregnancy; Pregnancy loss; Spontaneous abortion; Stillbirth