A new study says that all pregnant women should undergo thyroid screening in the first trimester of pregnancy.

"These findings add to the now increasing evidence from previous studies that all pregnant women, irrespective of their risk for thyroid problems, probably should be screened for thyroid dysfunction within the first three months of getting pregnant," said Jubbin Jagan Jacob, M.D., associate professor at Christian Medical College and Hospital, Ludhiana in Punjab, India. Dr. Jacob is the lead author of the study.

Even mild maternal thyroid hormone deficiency leads to neurodevelopment complications in the fetus, says a National Center for Biotechnology (NCBI) paper. Another study found that children born before 34 weeks to mothers who have thyroid dysfunction have lower cognitive skills.

It doesn't just stop there; a recent study found that girls born to mothers with thyroid dysfunction had altered thyroid function when they reach adolescence.

For the present study, researchers recruited around 1,000 pregnant women. All were screened for thyroid dysfunction during their first trimester. Approximately 233 women had mild thyroid dysfunction while 533 had no such dysfunction. The rest were diagnosed with having either hypothyroidism or hyperthyroidism. All those who had severe thyroid dysfunction were removed from the study.

The researchers then compared pregnancy outcomes of women who had normal thyroid or mild thyroid dysfunction. They found that women who had mild thyroid dysfunction had a seven times greater risk of having a still birth and the risk of miscarriage, pre-mature birth and low birth weight was double.

Researchers say that women must undergo thyroid screening test in their first trimester to prevent any complications associated with thyroid dysfunction because even mild dysfunction can lead to many serious complications.

"Our conclusions are that all pregnant women need to be screened for thyroid dysfunction at their first visit. This should form the basis for the national societies to make a change in their guidelines," Jacob said.

The study was presented at The Endocrine Society's 94th Annual Meeting in Houston and should be considered preliminary until published in a peer-reviewed journal.