Thyroid Screening During Pregnancy and Fetal Outcome

Abstract

Background: Physiological changes associated with pregnancy require an increased availability of thyroid hormones to meet the needs of both the mother and the fetus during pregnancy. This review will focus on the transient impairment of thyroid function during early pregnancy resulting in recurrent miscarriages and other adverse fetal outcomes. Objective: Our goal is to evaluate the relationship between subclinical hypothyroidism (SCH) and the risk of miscarriage before 20 weeks of pregnancy, and evaluate whether screening should be implemented in pregnant women at risk of SCH. Methods: Through the process of a structured literature review, PubMed, Scopus and Medline was searched from 2003 to 2017. The following search terms were used: subclinical, hypothyroidism, thyroid, and miscarriage. The following search terms were filtered out of our search: postpartum, autoimmunity, autoimmune, in vitro, and menstrual irregularity. Studies comparing the prevalence of miscarriage before 20 weeks of pregnancy and subclinical hypothyroidism were selected. Results: Six articles satisfying the inclusion criteria were analyzed. Pregnant women with untreated SCH had a higher prevalence of miscarriage in the first 20 weeks of pregnancy when compared to pregnant women who had received medical intervention. Higher maternal Thyroid-stimulating Hormone (TSH) levels even within the normal reference range are associated with an increased risk of recurrent miscarriage. Evidence suggests that treating SCH in pregnant women in their first trimester can prevent recurrent miscarriage as well as other adverse obstetric outcomes associated with SCH. Conclusions: Screening for Thyroid-stimulating hormone (TSH) and Thyroxine (T4) levels in pregnant women with a higher risk of SCH can prevent multiple obstetric complications. However, further research is needed to determine the hormone levels required during specific stages of gestation. This would have a positive impact on diagnosis and future medical interventions for maternal and fetal health.