Thyroid screening in pregnancy

Area of Science:

• Obstetrics and Gynecology
• Endocrinology
• Perinatal Medicine

Background:

• Subclinical thyroid dysfunction in pregnancy is debated, with observational studies suggesting risks to neurodevelopment and pregnancy outcomes.
• Existing recommendations for screening are not fully evidence-based, and prevalence estimates may be exaggerated.
• Overt hypothyroidism's adverse pregnancy impact is established, but subclinical forms warrant further investigation.

Purpose of the Study:

• To evaluate the efficacy of antenatal screening and treatment for subclinical thyroid dysfunction in pregnant women.
• To determine if treating subclinical thyroid dysfunction during pregnancy improves offspring neurodevelopmental outcomes.
• To provide evidence-based recommendations regarding routine thyroid screening in pregnancy.

Main Methods:

• The Controlled Antenatal Thyroid Screening (CATS) trial screened nearly 22,000 pregnant women.
• Maternal thyroid dysfunction (elevated TSH or low free thyroxine) was treated in 390 women.
• Offspring cognitive function (mean IQ and IQ <85) at age 3 was compared between treated and untreated groups (404 children).

Main Results:

• Antenatal screening and maternal treatment for subclinical thyroid dysfunction did not significantly improve offspring mean IQ at age 3.
• There was no difference in the number of children with an IQ below 85 between the treated and untreated groups.
• These findings suggest no cognitive benefit from screening and treating subclinical thyroid dysfunction during pregnancy.

Conclusions:

• Routine antenatal screening for subclinical thyroid dysfunction is not currently warranted based on available evidence.
• The benefits of screening and treating subclinical thyroid disease in pregnancy do not outweigh the costs and potential harms.
• Further research, including ongoing trials, is needed to fully clarify the role of thyroid screening in pregnancy.