The research, which was conducted by scientists at the Foundation for Blood Research in Scarborough, Maine, demonstrated that pregnant women who are hypothyroid have a second trimester miscarriage risk that is four times the risk of other women.
In the Journal of Medical Screening, the researchers reported that in a study of 9,000 pregnant women, those pregnant women with elevated TSH (thyroid stimulating hormone) levels had a 3.8 percent risk of late miscarriage, compared to only 0.9 percent miscarriage risk in women who were not hypothyroid.
The study attributed six out of every 100 late miscarriages to an undiagnosed hypothyroid condition in the mother.
Source:
Allan, W.C. et. al. "Maternal thyroid deficiency and pregnancy complications: implications for population screening," Journal of Medical Screening, 7(3): 127-130; doi:10.1136/jms.7.3.127 Online

