Hyperthyroidism and hypothyroidism can complicate pregnancy and cause issues for both the mother and fetus. Hyperthyroidism occurs in 2 per 1000 pregnancies and can lead to miscarriage, preterm delivery, preeclampsia, and cardiac failure in the mother as well as intrauterine growth restriction and premature birth in the fetus. It is caused by thyroid stimulating antibodies crossing the placenta and producing neonatal hyperthyroidism. Hypothyroidism can cause complications like preeclampsia and anemia if untreated. Treatment involves monitoring thyroid levels and adjusting medication doses as thyroid needs increase in pregnancy.