Thyroid Testing

Too-low thyroid levels can impair your child’s I.Q. So why aren’t all pregnant women being screened?

Starting with the drugstore kit that confirms you’re expecting, you’ll undergo scores of screenings, urinalyses, ultrasounds and other tests during pregnancy. Yet few expectant women undergo thyroid testing, a fact that disturbs some experts. When moms-to-be with thyroid problems go untreated, they’re more likely to have pregnancy complications, and their children may be at risk for decreased IQ.

The thyroid, a butterfly-shaped gland at the base of the neck, produces hormones that regulate metabolism. Weight, body temperature, energy, heart rate and even emotions can be affected when the thyroid releases too much or too little hormone. Either problem can lead to miscarriage, premature birth and preeclampsia, but having an underactive thyroid, or hypothyroidism, is especially disquieting because it can harm the fetal brain.

Hypothyroidism is usually caused by an autoimmune response in which antibodies attack the thyroid gland. Between 10 percent and 20 percent of women of childbearing age test positive for these antibodies, and 2 percent to 3 percent have thyroid levels that are too low. Paradoxically, pregnancy can disguise the signs. The symptoms of low thyroid, including fatigue, weight gain, constipation and dry skin, are also classic complaints of healthy expectant women.

Missing the women at risk

Ten years ago, James Haddow, M.D., found that children whose mothers had undetected thyroid deficiency during pregnancy had IQs that averaged 7 points lower than the offspring of women with healthy thyroids. Twenty percent had IQs below 85, a level that makes school and everyday life difficult. When Haddow, a research professor at the Warren Alpert Medical School of Brown University in Rhode Island, retested the women 10 years after pregnancy, he found that two-thirds had permanent hypothyroidism—and that on average, five years had elapsed before they were diagnosed.

Most obstetricians test only those pregnant patients who have obvious symptoms or a family history of thyroid problems. But researchers say this “high-risk” approach misses nearly one-third of women whose low thyroid levels could be remedied with safe, inexpensive medication. The American Association of Clinical Endocrinologists recommends testing before pregnancy and in the first trimester, but other doctors’ groups demur. Some claim the cost would be unwarranted or that test results are too difficult for OBs to interpret; others are waiting for more data.

Haddow believes testing should be routine, and that until it is, moms-tobe should ask their doctor to measure their thyroid function. “Pregnancy is an opportune time for making the diagnosis early,” he says, because it benefits the mom along with her fetus. Without testing, Haddow says, an affected woman will experience compromised day-to-day functioning until she is finally diagnosed.  “This is especially important during the early months of her baby’s life,” he adds.
 

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