Hypothyroidism in Pregnancy

Hypothyroidism during a pregnancy can lead to poor outcomes. Proper diagnosis and treatment can help. 


Conditions associated with hypothyroidism in pregnancy

  • Preeclampsia and gestational hypertension
  • Placental abruption
  • Nonreassuring fetal heart rate tracing
  • Preterm delivery, including very preterm delivery 
  • Low birth weight  
  • Increased rate of caesarean section 
  • Perinatal morbidity and mortality
  • Neuropsychological and cognitive impairment
  • Postpartum hemorrhage
  • Neuropsychological impairment is associated with subclinical hypothyroidism. In some studies, offspring (at age 3 and 9 years) of mothers who had low serum free T4 concentrations during the first trimester had lower mean intelligence, psychomotor, or behavioral scores compared with children born to women with normal thyroid function during gestation. Screening for thyroid disease during pregnancy is not yet standard of care. Assuming a baseline prevalence of 2.5 percent for subclinical hypothyroidism in pregnant women, one study calculated that for every 100,000 pregnant women screened, over 8 million dollars would be saved due to improved neonatal outcomes. (1) 

Women that should be screened for thyroid disease

  1. Women with a history of thyroid dysfunction.
  2. Women with a family history of thyroid disease.
  3. Women with a goiter.
  4. Women with thyroid antibodies. 
  5. Women with symptoms or clinical signs suggestive of hypothyroidism. 
  6. Women with type I diabetes, in whom the rate of development of new onset hypothyroidism in pregnancy was 16% in one series.
  7. Women with a history of either miscarriage or preterm delivery.
  8. Women with other autoimmune disorders that are frequently associated with autoimmune thyroid dysfunction, including vitiligo, adrenal insufficiency, hypoparathyroidism, atrophic gastritis, pernicious anemia, systemic sclerosis, systemic lupus erythematosus, and Sjgren’s syndrome.
  9. Women with infertility.
  10. Women with prior therapeutic head or neck irradiation.
  11. Women with morbid obesity. A body mass index .40 kg/m2 has been associated with an increased prevalence of hypothyroidism.
  12. Women age 30 or older. The prevalence of hypothyroidism increases with age. The prevalence of an elevated serum TSH (>5 mIU/L) increases from about 4% in women age 18–24 years to almost 7% in women aged 35–44 years

Thyroid hormone treatment during pregnancy 
Women with pre-existing hypothyroidism will need more thyroid hormone during pregnancy, and the goal of therapy is to normalize the mother's serum TSH concentration.Some women need an increase of 30-50% of their usual doses during pregnancy. This increase may occur as early as the 5th week of gestation. The endocrinologists at Houston Thyroid will manage these dose changes through a pregnancy
 
 

Autoimmune disease and hypothyroidism

Even in women with "normal" thyroid levels, the TPO antibodies can cause miscarriage and problems with delivery. Learn about management of autoimmune thyroid disease in pregnancy.


References:
1) Casey, BM, Dashe, JS, Wells, CE, et al. Subclinical hypothyroidism and pregnancy outcomes. Obstet Gynecol 2005; 105:239.
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