Controversial Screening for Thyroid Dysfunction in Preconception and Pregnancy: An Evidence-Based Review

Abstract

Objective: To evaluate the recommendations on the most adequate screening method (universal or selective) for thyroid dysfunction. Although thyroid dysfunction is a common disorder in fertile women and untreated cases may have negative maternal, fetal and neonatal outcomes, its screening in preconception and early pregnancy is controversial.
 Materials and methods: An evidence-based review was conducted to identify publications since 2017 of American Thyroid Association (ATA) guidelines, according to the following Population, Intervention, Comparison, Outcomes and Study (PICOS): women in preconception or pregnancy without thyroid disease who underwent universal or selective screening for thyroid dysfunction. Study selection obeyed the PRISMA criteria.
 Results: We included 15 of 325 publications. The 2017 ATA guidelines recommend selective screening in both preconception and pregnancy. The only two reviews on preconception recommended universal screening. For pregnancy, nine articles suggested universal screening, while a prospective study advocated selective screening. The main benefits advocated for universal screening were easy and low-cost tests; absence of missed diagnosis; safe and inexpensive treatment and its potential in preventing negative outcomes. Iodine deficiency is a decisive indication, but it was not evaluated in all clinical studies. Screening harms and knowledge gaps were the main arguments against universal screening. There are very few cost-effectiveness studies.
 Conclusion: We recommend universal screening for thyroid dysfunction in early pregnancy, which is a distinct point of view from 2017 ATA guidelines (weak recommendation, low-quality evidence). It is not possible to make a formal recommendation for preconception (insufficient evidence). We strongly suggest an individualized analysis by each country.

A case of overt hyperthyroidism: A forgotten cause of poor maternal-fetal outcome in low-resource settings

“…Given the association between thyroid disease and unfavorable pregnancy outcomes, the question of whether or not universal thyroid screening during pregnancy should be implemented has sparked debate. The low prevalence of thyroid disorders reported in the literature and the varying levels of thyroid-stimulating hormone across the globe are central to this discussion [9].…”

Update on therapeutic use of levothyroxine for the management of hypothyroidism during pregnancy

“…Reviewing relatively recent literature on this topic (2015 onwards), those in favour of universal screening for thyroid dysfunction in pregnancy point to the relatively high prevalence of thyroid disorders, the existence of low-cost tests (TSH, T4) and treatment (LT4), the potential of screening to avoid the potential devastating consequences of undiagnosed thyroid disease at this time, its cost-effectiveness, and a better prospect of finding most or all cases, compared with a targeted screening approach focussed on individuals with risk factors for thyroid disease ( 58 , 59 , 60 , 61 ). In one study, targeted screening focussed on women with at least one risk factor for hypothyroidism found that this approach was more effective for detecting overt hypothyroidism than SCH (except for obese Caucasian women, where both were detected) ( 62 ).…”

Thyroid Dysfunction in Pregnancy: A Literature Review

“…Total thyroxine and the FT4 index can also be measured in its place. Definitive screening is performed only in high-risk pregnant women (Figure 3) using serum TSH measurements [16], [17]. One study found that selective screening for high-risk women will be lost 30% of those with subclinical hypothyroidism.…”