Screening only pregnant women felt to be at high-risk for thyroid problems may mean that many women with thyroid dysfunction may escape detection, according to UK researchers.

There is increasing evidence that even a mild “hypothyroidism” during pregnancy is associated with impaired neurological and psychological development of children, lead investigator Dr. Bijay Vaidya told Reuters Health.

“Whilst there is general consensus that thyroid deficiency - overt and mild - during pregnancy should be promptly and adequately treated ... to prevent these adverse outcomes, current guidelines do not recommend universal screening of thyroid function in all pregnant women,” he noted. “The guidelines recommend testing thyroid function only in high-risk pregnant women.”

To gauge the impact of this policy, Vaidya, of Devon and Exeter Hospital, Exeter, and colleagues prospectively studied pregnant women.

At a median of 9 weeks of gestation, they checked thyroid hormone levels in 1,327 women. Of this group, 413 were deemed to be at high risk for abnormal thyroid function because of a personal history of thyroid or other autoimmune disorders or a family history of thyroid disorders.

Forty women (2.6 percent) had raised thyroid-stimulating hormone (TSH) levels. This amounted to 6.8 percent of the high-risk group and 1 percent of the low-risk group. Specific risk factors included a personal history of thyroid problems or a family history of such disorders.

However, the researchers point out that 12 of this group of women with raised TSH (30 percent) were not considered to be at high risk.

Thus, concluded, Vaidya, “our study shows that without universal thyroid screening, about one-third of the pregnant women with thyroid deficiency will be missed.”

In an accompanying editorial, Dr. Gregory A. Brent of the University of California, Los Angeles, notes that as tools to diagnose and intervene are easily accessible, leaving mom’s thyroid disease undiagnosed “is no longer acceptable.”

SOURCE: Journal of Clinical Endocrinology and Metabolism, January 2007.