1 Department of Public Health - Department of Epidemiology, Department of Public Health, Health, Aarhus University2 Department of Clinical Medicine - Medicinsk Endokrinologisk Afdeling, Aalborg Sygehus, Department of Clinical Medicine, Health, Aarhus University3 Department of Clinical Medicine, Health, Aarhus University4 Department of Public Health - Department of Epidemiology, Department of Public Health, Health, Aarhus University5 Department of Clinical Medicine, Health, Aarhus University
A Danish National Hospital Register Study
OBJECTIVES: Maternal hyper- and hypothyroidism have been associated with increased risk of adverse pregnancy outcomes, but studies have led to inconsistent results. We aimed to identify children born to mothers with a hospital-recorded diagnosis of thyroid dysfunction in Denmark and to study the association with gestational age at delivery and birth weight of the child. STUDY DESIGN: Population-based cohort study using Danish nationwide registers. All singleton live births in Denmark between January 1, 1978 and December 31, 2006 were identified and stratified by maternal diagnosis of hyper- or hypothyroidism registered in the Danish National Hospital Register before January 1, 2007. RESULTS: Maternal first-time diagnosis of thyroid dysfunction before, during or after pregnancy was registered in 32,809 (2.0%) of the singleton live births (n = 1,638,338). Maternal diagnosis of hyperthyroidism (adjusted OR 1.22, 95% CI 1.15-1.30) and hypothyroidism (adjusted OR 1.17, 95% CI 1.08-1.27) were associated with increased risk of preterm birth. Moreover, birth weight in children born to mothers with a diagnosis of hyperthyroidism was lower (adjusted difference -51 g, 95% CI -58 to -43 g) and higher in relation to maternal hypothyroidism (adjusted difference 20 g, 95% CI 10-30 g). Hyperthyroidism was associated with small-for-gestational-age (adjusted OR 1.15, 95% CI 1.10-1.20) and hypothyroidism with large-for-gestational-age children (adjusted OR 1.24, 95% CI 1.17-1.31). CONCLUSIONS: Based on Danish nationwide registers, both maternal hyper- and hypothyroidism were associated with increased risk of preterm birth. Actual birth weight of the child and birth weight for gestational age were low if the mother had a diagnosis of hyperthyroidism and high if the diagnosis was hypothyroidism.
European Thyroid Journal, 2013, Vol 2, Issue 2, p. 135-144