Thyroid Disease and Pregnancy

Thyroid disease is not as common as diabetes in pregnancy, but it is relatively common and can have far reaching effects. Thyroid hormone has to be produced in the right amounts, the levels can be too high or too low and produce complications for pregnancy. The complications can be for the mother: high blood pressure, or diabetes, or heart effects and there is a rare condition called thyroid storm. For the baby thyroid disease can lead to miscarriage, premature birth, small growth, stillbirth, or complications of the placenta. Fortunately, for most, treatment of thyroid disease produces a healthy outcome in pregnancy. We think that the trigger for many thyroid function problems in pregnancy include viral diseases, environmental factors such as diet and genetic predisposition; most women have an increase in thyroid binding globulin when pregnant and in fact the HCG from the placenta stimulates thyroid, so it's most likely some one will be too high rather than too low.  The thyroid gland will enlarge in pregnancy by about 10 or 20 %, and it is up to your gyno to determine if your gland is enlarged as typical in pregnancy or needs a study such as an ultrasound to determine if the gland has nodules in it. Thyroid tests are fairly straight forward for your gyno, they are done on blood and relatively easy to interpret in most cases. The test of TSH which is a pituitary hormone is the first test,  most important and accurate test there is. In prgnancy the actual thyroid hormones, T3 and T4 will increase. Thyroid antibodies often occur as individuals get older, and tests of antibodies are really used in the most complex cases as treatment in most cases will not be affected by these antibodies. The thyroid gland is under stress and strain from pregnancy alone, it has to work about half again as hard to produce the hormones to keep up with the demand of pregnancy which is why the levels of T3 and T4 go up , so it is very important for a pregnant patient. As for background information your thyroid gland runs your metabolism, and it is subject to stresses from environmental factors, genetic predisposition and even viral infections. Thyroid function also directly and indirectly affects whether you get pregnant and how healthy that pregnancy is. To accommodate the need for extra thyroid hormone in pregnancy the thyroid gland as we said enlarges but it shouldn't take on actual nodules. If the thyroid level in pregnancy cannot go up to accommodate the body's extra needs complications can occur. Higher miscarriage rates, more frequent preterm deliveries, increased risk of high blood pressure, more patients becoming diabetic and having diabetic complications, higher risk for placental problems like premature separation, and adverse fetal effects have all been reported with thyroid disease when you are pregnant! In women with thyroid disease at least half of implanted embryos will not survive to delivery,with most of these pregnancy losses occur in the first trimester.Although there are many contributing factors both having high and low thyroid tests are actually associated with miscarriages.
Because these antibodies to the thyroid are more common in pregnancy thus women are more likely than men to have antibodies against the thyroid. And the older your age the frequency  of having these antiboties increases, so having a pregnancy when you are older predisposes you to having a pregnancy with thyroid problems. We can explain this greater need for thyroid hormone in pregnancy by several biological mechanisms. The placenta takes some hormone and the fetus takes some thyroid hormone, as well as a need for the increased weight and nutrition of pregnancy for our bodies to accommodate a pregnancy. At 6 weeks of pregnancy there is already evidence of mom's thyroid hormone in the fetus, as the fetus itself doesn't really make it's own until 20 weeks along. So some experts argue that thyroid hormone levels in pregnancy should be thus kept even higher than in the non-pregnant woman. This means a "normal" test may not actually be a normal healthy level of thyroid. Then a group from the University of Texas Southwestern reporting tin the November 2011 American Journal of Obstetrics & Gynecology has now found that the more pregnancies a woman has the more she has elevated antibody levels against components of the thyroid. Specifically it has now been shown that it may be related to certain characteristics of the fetus and what their cells actually were. And the more pregnancies a woman has had the more anti-thhyroid peroxidase antibodies she would have. So those women, with more pregnancies are even more likely to have thyroid problems in pregnancy, and after pregnancy, no matter how long that pregnancy actually lasted. It may be recommended for women who have had a miscarriage to look into their thyroid levels carefully before a next pregnancy.Something else to talk to your gyno about!


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