Lee SY, et al. - In pregnancy, adverse effects can occur because of both hyperthyroidism and hypothyroidism. Gestational transient thyrotoxicosis and Graves’ disease are identified to be the most common causes of thyrotoxicosis in pregnancy. As these two entities differ in treatment options, their differentiation is important. Researchers emphasize counselling women of reproductive age diagnosed with Graves’ disease regarding the impact of treatment options on a potential pregnancy. The antithyroid medications can have teratogenic effects although the absolute risk is small. Relative to methimazole, propylthiouracil seems to have less severe teratogenicity and is therefore favored during the first trimester in cases with medication requirements. They emphasize advising women to delay pregnancy for at least 6 months following radioactive iodine to reduce potential adverse effects from radiation and ensure normal thyroid hormone levels prior to conception. As normal fetal development requires thyroid hormone, hypothyroidism is linked with adverse obstetric and child neurodevelopmental outcomes. Treatment of women with overt hypothyroidism with levothyroxine (LT4) is emphasized to a goal TSH < 2.5mIU/L. Mounting evidence has been generated for correlations of maternal hypothyroxinemia and subclinical hypothyroidism with pregnancy loss, preterm labor, and lower scores on child cognitive assessment. Although LT4 treatment to keep TSH within the pregnancy-specific reference range is associated with a minimal risk, controversies remain concerning treatment of mild maternal thyroid hypofunction, given the lack of clinical trials demonstrating improved outcomes with LT4 treatment.