Endocrine Abstracts

Thyroid diseases affect up to 4% of all pregnancies. Several evidence-based recommendations have been created to observe and treat thyroid diseases in pregnant women. We studied whether the diagnostics and treatment of hypothyroidism among pregnant women have improved in the course of time. Data consisted of all singleton pregnancies (N=571785) during 2004–2013 in Finland, collected from the Finnish Medical Birth Register (MBR). Data on maternal thyroid diseases were obtained from the MBR and the Hospital Discharge Register, and combined with the Special Refund Entitlement Register and the Register on Reimbursed Drug Purchases consisting data on medication purchases during the index pregnancy. Women with thyroid diseases other than hypothyroidism were excluded (N=4561), rendering a final study population of 567 224 singleton pregnancies. Pregnancies were divided into four categories: mothers with diagnosed hypothyroidism treated with levothyroxine (N=8893), mothers treated with levothyroxine without a recorded hypothyroidism diagnosis (N=6788) (mostly treated in the primary care), mothers with diagnosed hypothyroidism but without levothyroxine treatment (N=683) and mothers without thyroid diseases or thyroid medication (N=550 860). In 2004 approximately 1% of pregnant women had diagnosed hypothyroidism and were treated with levothyroxine. By 2013 this prevalence had more than doubled up to 2.4%. The prevalence of women receiving levothyroxine treatment without recorded hypothyroidism diagnosis was 0.2% in 2004 but 12-fold higher (2.5%) in 2013. The increase in prevalence of diagnosed hypothyroidism and levothyroxine treatment has been steady over time. Surprisingly, the prevalence of pregnant women with hypothyroidism and no recorded levothyroxine treatment has been constant between 0.1 and 0.2%. Our study shows that the diagnoses of hypothyroidism and use of levothyroxine treatment among pregnant women have increased markedly during the past 10 years. This suggests that clinical recommendations have improved the awareness on the risks of hypothyroidism on pregnancy and the threshold to treat hypothyroidism during pregnancy seems declining.