"Anyone who is having trouble getting pregnant or who has had a miscarriage should be screened," she says. Dr. Sadaty’s advice is to look at three different measures of thyroid health. Most doctors who check thyroid function will test your TSH (thyroid stimulating hormone) and free T4 levels. TSH is a hormone made by the pituitary gland in the brain, and it tells the thyroid to make thyroid hormones. A free T4 test tells you how much of this thyroid hormone is actually in your bloodstream.
The third test, a TPO (thyroid peroxidase) antibody test, is not always run, says Dr. Sadaty, but it's important. If you have TPO antibodies, it means that your body is trying to attack enzymes in the thyroid—in other words, that your thyroid disorder is a result of an autoimmune problem. She recommends this test because it's possible to have these antibodies for up to 10 years before you notice any symptoms. That's fine if you aren't trying to have a baby because mild thyroid dysfunction that doesn't cause symptoms usually doesn't need to be treated. But when you're trying to conceive, it's crucial to keep tighter control of your levels.
If you figure out that your thyroid is indeed problematic, treatment can help keep you and your future baby healthy. If you have hypothyroidism, which is significantly more common than hyperthyroidism, you'll need to take synthetic thyroid replacement hormones to make up for what your body is not producing. The catch is that your dose may need to be adjusted during pregnancy. "Your requirements for thyroid hormone can go up 25 to 50 percent when you're pregnant," says Dr. Sadaty. "You'll need to get screened every six to eight weeks, so your doctor can make adjustments."
After you've had a baby, you should also keep your thyroid in mind—even if you never had a thyroid disorder before. "A lot of women develop postpartum thyroiditis, which is when thyroid antibodies go up after childbirth," says Dr. Sadaty. Many times hyper- or hypothyroidism that kicks in for the first time after having a baby resolves in a few months, but if you have any symptoms, it's wise to stay in close touch with your doctor to make sure that your levels bounce back and you don’t need medication.