Severe preeclampsia was more common in women with subclinical hypothyroidism in a recent study, although the investigators say the clinical relevance of the finding is unclear.
"This has been an interesting biological finding but its clinical implications have yet to be established," Dr Karen L. Wilson said.
"More research has to be done to see if treatment of subclinical thyroid disease has any impact on the current findings," she added. "Until that is done, we cannot recommend universal thyroid screening in pregnancy."
At the University of Texas Southwestern Medical Center, Dallas, Dr Wilson and her colleagues conducted a secondary analysis of data from a prospective population-based study of nearly 25,000 women. All delivered singleton neonates weighing more than 500g over a 30-month period.
The overall incidences of hypertension in pregnancy were 6.2% in the 584 women with subclinical hyperthyroidism, 8.5% in the 23,771 women who were euthyroid, and 10.9% in the 528 with subclinical hypothyroidism, the researchers report in the issue of Obstetrics and Gynecology.
Before adjustment, these relationships were significant, but after allowing for race, age, and other factors, the only remaining significant association was in women with subclinical hypothyroidism, who had a 60% higher risk of severe preeclampsia.
The researchers say their findings "add to accruing data that subclinical hypothyroidism, a relatively common finding in women of childbearing age, may be associated with some adverse perinatal outcomes."
There's a trial underway now that's looking for possible advantages of intervention in subclinical thyroid disorders, according to the authors. In the meantime, they say, "We remain convinced that routine prenatal screening for thyroid disorders should not be implemented until clear benefit is established.
(Reuters Health, David Douglas, January 2012)