Thyroid Disease and the Unborn Fetus

" There is also an increased risk for mental retardation in infants whose mothers are severely deficient in iodine. A meta-analysis of 18 studies concluded that maternal iodine deficiency lowered offspring IQ score by 13 points.
             There has also been research showing that if the mother is treated for her deficiency during pregnancy, the fetus was able to develop normally. In one study, done in Xinjiang, China, it was concluded that the fetal brain was protected from the effects of iodine deficiency up through the second trimester. Another study states, "Women supplemented before conception or early in pregnancy have reduced neonatal mortality, and their children have improved IQ scores and fewer neurologic abnormalities when compared with control groups.".
             The thyroid gland secretes hormones that affect the cells in the body by delivering energy to those cells. It is essential for neuronal migration and myelination of the fetal brain. The maternal thyroid hormone is used for fetal thyroid development around 4 weeks after conception and continues until birth. Proper function of the thyroid is most crucial during 3 to 5 months of pregnancy. "Around the beginning of the second trimester, the fetal thyroid also begins to produce hormones but the reserves of the fetal gland are low; thus maternal thyroid hormones contribute to total fetal thyroid hormone concentrations until birth." When left untreated, children born to women with hypothyroidism have shown to have lower IQ than children born to healthy women. In addition to lower IQ scores, studies have also shown those children were at higher risk for neuropsychological development and learning disabilities. In many cases, women receiving a replacement dose of T4 during pregnancy were able to improve metabolism of maternal T4 and increased placental transport. .
             Other risks to the fetus from a mother with hypo or hyperthyroidism are premature birth and low birth weight.