Hi there! Thank you for your question. Hypothyroidism affects about 1% of pregnant women. Many of the symptoms normally occur in normal pregnancy. The symptoms include weight gain, poor appetite, tiredness, poor memory, change in appearance, depression, neck swelling, puffy eyes, dry, brittle skin and hair, joint pain, muscle pain and weakness, constipation, deafness, hallucination, slow reflexes, low heart rate and voice changes.

The investigations that will be done are TSH, T3 and T4 levels.There will be increased TSH (more than 2.5mIU/L) and reduced free T4. The complication of hypothyroidism could be divided to maternal and fetal complications. For maternal it includes pre-conception (fertility/menstrual disorders), increased miscarriages, anaemia, pregnancy induced hypertension, placenta abruptio (separation of the placenta from the uterine lining causing bleeding).

For fetus it includes impaired intellectual, preterm birth, low weight, acute respiratory distress syndrome and increases mortality. Routine screening for hypothyroidism during pregnancy is not recommended. A pregnant woman with symptoms of hypothyroidism, a history of hypothyroidism, or with other endocrine system conditions should be screened. Thyroid hormone replacement is used to treat the mother.

Dosage of thyroid hormone replacement therapy is based on the individual’s levels of thyroid hormones. Thyroid hormone levels may change during pregnancy. And, the thyroid replacement dosing may also change. Thyroid hormone levels need to be checked every 4 weeks during the first half of pregnancy. The treatment is safe and essential to both mother and fetus. Routine screening for all newborns includes a test of thyroid hormone levels.

A study concluded that there is insufficient evidence to recommend for or against universal screening of thyroid dysfunction in early pregnancy or preconception. Instead, it is recommended that all patients seeking pregnancy, or newly pregnant, should undergo clinical evaluation if any of risk factors or sign and symptoms for thyroid dysfunction is identified, testing for serum TSH is recommended.

So since you have a history of hypothyroidism, I suggest you go to your doctor and undergo screening. This is so that we can be reassured that your thyroid levels are safe for pregnancy. It also will help with proper management throughout your pregnancy.

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