Screening for thyroid dysfunction in pregnancy
The most controversial issue in the field of thyroid and pregnancy is whether clinicians should screen all pregnant women for thyroid disease, and the screening should be performed before pregnancy or at the first prenatal visit. This review aimed to discuss updates on the important issue of thyroid screening before conception and during pregnancy and to highlight the gap in evidence that has led to remarkable controversies on this topic. The terms “screening” AND “thyroid” AND “pregnancy” were used to search Medline for English-language papers published from 1990 to the end of January 2018. After reviewing of titles of 482 articles, we focused on high quality and important studies. With respect to the Wilson and Jungner criteria for disease screening, thyroid dysfunction screening before and during pregnancy is still a conflicting issue. Available data suggests that compared to the universal screening, the case finding screening would result in missing cases of thyroid dysfunction. The primary debate is regarding maternal, fetal and offspring benefits of treatment of mothers with subclinical hypothyroidism and/or thyroid autoimmunity. Results of few high-quality studies in this field are in favor of some benefit considering pregnancy outcomes but no significant beneficial impact on fetal and offspring outcomes. Likewise, cost-effectiveness studies support the concept of universal screening. More evidence is required to assess the advantages and disadvantages of two different screening strategies for thyroid dysfunction in pregnancy, focusing on maternal, neonatal and offspring health outcomes following diagnosis and treatment of thyroid dysfunction, especially subclinical hypothyroidism in pregnancy. Moreover, screening strategies need to be individualized for each country according to disease burden, case finding costs and available health services.