Is universal screening in pregnant women a beneficial, safe and cost-effective option?

Studies have shown benefits of universal screening

There has been much discussion in the endocrine and obstetrical literature during the last few years regarding whether all pregnant women should be screened for thyroid disease. In order to advocate screening, four criteria need to be met: the disease should be common; the disease should have important comorbidities associated with it; the disease should have a universally available, reliable and inexpensive screening test; and treatment should result in a decrease in cormobidities.

Alex Stagnaro-Green

One, thyroid disease in pregnancy is common. Overt thyroid disease is seen in 0.7% of all women (0.3% overt hypothyroidism; 0.4% overt hyperthyroidism) and subclinical thyroid disease is present in 5.2% of all pregnant women (2.2% subclinical hypothyroidism; 3% subclinical hyperthyroidism). Furthermore, approximately 10% to 15% of all pregnant women are thyroid autoantibody positive.

Two, overt thyroid dysfunction — both hyperthyroid and hypothyroid — is associated with multiple fetal and maternal abnormalities, including miscarriage, preterm delivery and maternal hypertension. Subclinical hypothyroidism has been shown to be associated with miscarriage and preterm delivery. Thyroid antibody positivity in euthyroid women has been associated with a two- to fourfold increase in miscarriage.

Three, thyroid-stimulating hormone and thyroid peroxidase antibodies are universally available, reliable and inexpensive.

Finally, it is widely accepted that treatment of overt thyroid disease decreases maternal and neonatal complications. This means that universal screening will result in the detection and treatment of one case of overt thyroid disease out of every 141 pregnant women screened. Furthermore, recent research has shown that treating thyroid peroxidase antibody positive women with TSH levels above 2.5 mIU/L decreases maternal and neonatal complications. Other studies have shown that screening and treatment for thyroid disease in pregnancy is cost-effective.

The data are clear. It is time for universal screening.

Alex Stagnaro-Green, MD, is professor of obstetrics, gynecology and women’s health at New Jersey Medical School, University of Medicine & Dentistry of New Jersey.

Universal screening can potentially create added stress, anxiety

We live in an evidence-based medical society, and there are not enough data at present to wholeheartedly embrace screening. In Cardiff, Wales, we conducted a randomized trial that screened 22,000 women and measured the IQs of about 800 children whose mothers had a high thyroid-stimulating hormone or low free thyroxine levels; half of the mothers received thyroid hormone in pregnancy. While the full analysis is not available, results thus far seem consistent with an approach to screening; however, these data are preliminary. Once this study is presented and combined with another large NIH trial, we may very well be able to push for broader screening — but we simply are not there yet.

John H. Lazarus

Another concern is that introducing a screening procedure for any disease or condition may also add stress and anxiety for patients. False positives and false negatives are always going to occur. Even if there is a 0.1% error rate, with 4 million pregnancies in the United States each year, this amounts to 40,000 errors. In any screening situation, the patient is typically anxious because they have to undergo a test, understand what the test is for and then wait for the results.

That aside, I believe there are tremendous advantages to screening when considering risk vs. reward. Studies have shown that women with subclinical hypothyroidism in early pregnancy have more obstetric-related adverse events, such as preeclampsia and preterm delivery.

Studies also show that women with an untreated, high TSH during pregnancy had children with lower IQs compared with children of women who had a normal TSH; these children were studied at age 7 years, making these results quite valid. Our own preliminary data endorse the positive effect on IQ.

The topic of universal screening for thyroid disease in pregnancy is not a black and white area. While I believe that there is an array of benefits, I am not completely convinced. I would estimate that I am, at this moment, 85% in favor of screening, with a few caveats preventing me from being totally on board.

John H. Lazarus, MD, is professor of clinical endocrinology at Cardiff School of Medicine in Cardiff, Wales.