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Sunday, 20 January, 2002, 00:24 GMT
Thyroid disease 'raises birth risk'
A scan may be necessary
Women with thyroid disease are more likely have babies with birth defects even if tests show no problem with the gland during pregnancy, say researchers.

However, a British expert has taken issue with the findings, which he said were "suspicious".

A study by Johns Hopkins University also showed that babies born to women with overactive or underactive thyroid were at increased risk of heart, brain or kidney defects.

The link with birth defects is new and unexpected

Dr David Nagey
They were also more likely to have other anomalies, including cleft lip or palate, or extra fingers.

In addition, infants born to women with underactive thyroid were at increased risk of cardiac problems even if the mothers were on medication.

UK doctors warned in December that thousands of pregnant women and their babies are being put at risk because the NHS does not routinely screen for thyroid problems.


The new research contradicts some earlier studies indicating thyroid disease did not pose foetal risks.

However, those studies were conducted using less sophisticated technology for detecting birth defects.

Researcher Dr David Nagey said: "We already knew that there was an increased risk of problems, mostly intellectual or developmental, in children as a result of hypothyroid (underactive thyroid) pregnancies, but the link with birth defects is new and unexpected.

"If these results are confirmed, it could lead to routine testing of women for thyroid disease prior to pregnancy and for cardiac anomalies in the foetuses of women with hypothyroidism."

Dr Nagey recommends that doctors consider adding thyroid testing to the routine prenatal diagnostic tests.

If the test indicates the woman has hypothyroidism, a foetal echocardiogram during the 20th week of pregnancy might be warranted.

Birth defects

The researchers studied 101 women (64 with hypothyroidism and 50 with the overactive version, hyperthyroidism) who gave birth at The Johns Hopkins Hospital between December 1994 and June 1999.

Overall, there were 108 pregnancies with 114 foetuses.

Twenty-one babies (18%) had birth defects, including problems in the cardiac, renal and central nervous systems and other disorders such as sunken chest, extra fingers, cleft lip and palate, and ear deformities. Two foetuses died before being delivered.

The women with hypothyroidism were more likely than those with hyperthyroidism to have babies with defects.

Dr Nagey believes it is possible the same antibodies that cause the underactive thyroid also could be responsible for the birth defects.

Professor David James, an expert in foetal medicine from the Queen's Medical Centre, Nottingham, told BBC News Online he was "very suspicious" of the data.

He said: "Eighteen percent is such a high incidence of birth defects in the pregnant women with thyroid disease that if it were as straightforward as that then one might have expected others would have found the association before now."

The research was presented at a meeting of the Society for Maternal-Fetal Medicine in New Orleans.

See also:

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