Hashimoto’s disease is an autoimmune condition where the body’s immune system mistakenly attacks the thyroid gland, leading to hypothyroidism, a state of low thyroid hormone production. Thyroid hormones regulate metabolism and multiple body systems, including reproductive function. Getting pregnant with Hashimoto’s is possible, but it requires careful planning and management of thyroid hormone levels before and throughout pregnancy.
Hashimoto’s Effect on Conception
The primary complication affecting fertility in women with Hashimoto’s is hypothyroidism. Insufficient thyroid hormone levels disrupt the reproductive system, interfering with sex hormone production and leading to irregular menstrual cycles or cessation of ovulation.
The presence of thyroid peroxidase (TPO) antibodies, the autoimmune aspect of the disease, is also associated with a higher risk of infertility, even when hormone levels are normal. However, the most direct barrier remains the functional state of the thyroid gland. Restoring thyroid hormone levels to a healthy range normalizes the menstrual cycle, allowing for regular ovulation and increasing the likelihood of implantation.
Preparing for Pregnancy
Pre-conception planning is the most important step for women with Hashimoto’s who wish to become pregnant. This phase should begin months before attempting to conceive and involves close consultation with an endocrinologist and an obstetrician. The goal is to achieve a tightly controlled thyroid-stimulating hormone (TSH) level, significantly lower than the standard adult range. Current guidelines recommend optimizing the TSH level to be below 2.5 mIU/L before conception occurs. For women already taking levothyroxine, this means adjusting the dose to bring the TSH into the lower end of the normal range, and consistent daily intake is paramount.
Managing Thyroid Health During Pregnancy
Once pregnancy is confirmed, the body’s demand for thyroid hormone increases dramatically, often requiring an immediate adjustment to the levothyroxine dose. This increased need is driven by higher estrogen levels and the developing fetal-placental unit, which accelerates the breakdown and transport of thyroid hormones. Many women will need to increase their levothyroxine dose by approximately 20% to 50% early in the first trimester. It is recommended to increase the dose by two pills per week immediately upon a positive pregnancy test, even before the first blood test.
Untreated hypothyroidism during pregnancy poses significant risks to both the mother and the developing fetus. Maternal complications include an increased risk of miscarriage, preeclampsia, and preterm birth. For the baby, untreated maternal hypothyroidism in the first trimester can negatively impact neurological development. To maintain proper control, thyroid function must be monitored frequently, typically every four to six weeks throughout the pregnancy, with TSH targets remaining low.
Postpartum Monitoring and Risk
After delivery, the intense physiological demands on the thyroid quickly subside, and the levothyroxine dose usually needs to be reduced back to the pre-pregnancy level. This dose reduction often happens shortly after the baby is born, but continued close monitoring is necessary due to the risk of Postpartum Thyroiditis (PPT). Women with pre-existing Hashimoto’s disease are significantly more likely to develop PPT in the year following childbirth. PPT involves a temporary inflammation of the thyroid, causing a brief period of hyperthyroidism followed by a longer phase of hypothyroidism.
Symptoms like fatigue, mood swings, and anxiety during this period are frequently mistaken for normal fatigue or “baby blues.” Because of this, thyroid function should be checked approximately six weeks postpartum and then regularly for up to one year. While PPT is often temporary, a portion of affected women will develop permanent hypothyroidism, emphasizing the importance of long-term follow-up care.