1. Hyperthyroidism and pregnancy: Hyperthyroidism occurs in women of childbearing age between 20 and 40 years old. Therefore, pregnant women are more likely to develop hyperthyroidism and to become pregnant during the treatment of hyperthyroidism. In mild cases, it usually does not affect ovulation and may lead to pregnancy, while in severe cases, about 90% of patients do not ovulate, leading to infertility. Once a patient with hyperthyroidism becomes pregnant, if her condition is not yet stable, she is prone to miscarriage, preterm delivery, malformation, low fetal weight and fetal distress, with a miscarriage rate of 26% and a preterm delivery rate of 15%. At the same time, maternal thyroid-stimulating antibodies (TSAb) can enter the fetus through the placenta and may cause neonatal hyperthyroidism. At the same time, pregnancy can increase the physiological burden of hyperthyroidism, and pregnant women often take insufficient doses of medication or do not take medication for fear of affecting the fetus, which can aggravate hyperthyroidism and even trigger thyroid crisis, threatening the patient’s life. The mother may increase the dosage of medication when her condition worsens, which may suppress the thyroid function of the fetus and lead to neonatal hypothyroidism (cretinism). Therefore, it is dangerous for a woman with hyperthyroidism to become pregnant, which is not good for both mother and child! From a eugenic point of view, it is important not to get pregnant while suffering from hyperthyroidism. In case of accidental pregnancy, it is recommended to terminate the pregnancy as soon as possible within 3 months, considering the double negative effects of hyperthyroidism pregnancy. Once a patient with severe or untreated hyperthyroidism becomes pregnant, he or she should not hesitate to have an abortion. Some scholars suggest that pregnancy can be considered for those who have been controlled by regular treatment of hyperthyroidism for one to two years and have not seen any recurrence after six months of drug withdrawal. The author holds a different opinion. Clinically, many patients with hyperthyroidism start to relapse six months to one year after stopping medication, so pregnancy during this period may coincide with the relapse of hyperthyroidism. Some scholars also suggest that it is more likely that the patient will be cured when there is no relapse 1 to 2 years after stopping the medication, so it is safer to choose pregnancy again. In my opinion, for those who have relapsed hyperthyroidism or need to consider pregnancy in the near future, direct surgery or iodine-131 treatment is recommended to eliminate the dilemma of recurrence of hyperthyroidism after pregnancy. 2. Drug treatment options and precautions: If the patient is older and less ill and insists on continuing the pregnancy, we should let the patient know that the effect of hyperthyroidism itself on the fetus is greater than the effect of anti-thyroid drugs, so necessary treatment should be given. The most commonly used is propylthioxypyrimethamine (PTU). PTU has a large molecular weight when combined with proteins in the pregnant woman’s body, and the amount entering the fetus is small, and it can inhibit the conversion of peripheral T4 to T3, so it has become the drug of choice during pregnancy. The maximum dose should not be greater than 200 mg per day. If the symptoms are still difficult to control, you can add drugs such as insulin as appropriate. During pregnancy, thyroid function should be closely monitored and the dose of propylthiouracil should be adjusted in time to keep the thyroid function at the upper limit of normal value. The last trimester of pregnancy is the stage of rapid fetal brain development, so propylthiouracil should not be overdosed. During pregnancy, thyroid binding globulin increases due to the influence of estrogen levels, and serum T4 may be increased, but free T4 is normal, so the level of free thyroxine should be analyzed during the thyroid function test. At the same time, the concentration of thyroid receptor antibody (TRAb) should be measured regularly during pregnancy. If TRAb is several times higher than the normal value, it indicates a higher possibility of fetal hyperthyroidism, so that physicians can take timely measures to treat neonatal hyperthyroidism. 3. Precautions during pregnancy: Pregnant women with hyperthyroidism should be examined and followed up in high-risk clinics to enhance fetal monitoring and prenatal care. Ultrasound examination of the fetus should be performed once every one to two months to understand the growth of the fetus; in late pregnancy, fetal heart monitoring should be performed once or twice a week to pay attention to fetal distress, fast or slow fetal heart rate, etc.; at 37 to 38 weeks of pregnancy, it is appropriate to be admitted to the hospital for monitoring and waiting for delivery. At the same time, the pregnant women should strengthen nutrition, pay attention to rest, adopt left side lying position, and avoid infection, mental stimulation and mood swings to avoid hyperthyroidism crisis. Because hyperthyroidism is easily complicated by hyperemesis, it is especially important to pay attention to early calcium supplementation and observe whether there is edema, elevated blood pressure and urine protein. Most of the pregnant women with hyperthyroidism can deliver vaginally without any problems. If there is any cephalopelvic disproportion, abnormal fetal position or fetal distress during delivery, the delivery should be changed to cesarean section in time to avoid prolonged labor and fatigue of the mother, which may lead to hyperthyroidism crisis during delivery. In addition, pregnant women with hyperthyroidism generally have stronger contractions, smaller fetuses, shorter labor, and higher rate of neonatal asphyxia, so they should be prepared for neonatal resuscitation. 4. Delivery and breastfeeding: When the newborn is born, cord blood should be left to check thyroid function and related antibodies, and the size of the thyroid gland and the presence of murmurs should be checked. Hyperthyroidism in newborns is rare and usually occurs within a few days or a week after delivery. The child may show enlarged thyroid gland, protruding or open eyes, high skin temperature, crying, large food intake, frequent bowel movements, weight gain, severe hyperthyroidism with high fever, fast heart rate, fast breathing, etc.; while in case of low thyroid, the child often shows poor response, no crying, little food, delayed bowel movements, weight gain. It should not be overlooked that the condition of hyperthyroidism may recur or worsen when the immunosuppression is lifted after delivery. Therefore, it is necessary to continue taking the medication after delivery and to increase the dose of medication appropriately, as well as to monitor thyroid function. Can mothers treated with propylthiouracil breastfeed? The traditional view is that mothers taking ATD should not breastfeed because the concentration of these drugs in breast milk is thought to affect fetal thyroid function. However, in 1980, Kampmann et al. published a report suggesting that there was no significant aggregation of PTU in breast milk. 9 breastfeeding women were given 200 mg of PTU and the drug concentrations in serum and breast milk were measured for 4 hours. The drug concentration in breast milk is 10% of the serum drug concentration for the same period. The concentration of PTU in breast milk was found to be 10% of the serum concentration of the drug during the same period, and based on this amount, if a mother takes 600 mg of PTU per day, which is equivalent to giving 149 μg to her infant, this drug concentration for a 4 kg infant is equivalent to 3 mg of PTU per day for a 70 kg adult. The first choice is PTU during lactation. Studies have shown that when mothers take PTU while breastfeeding, their offspring’s mental and physical development is not affected and no complications such as granulocytopenia or liver damage have been observed. It is recommended that mothers should take PTU after breastfeeding, with an interval of 3 to 4 hours before the next breastfeeding, and that the infant’s thyroid function must be monitored while taking the drug. Although it is safe for mothers to be treated with PTU while breastfeeding, I believe it is more comfortable to hand-feed at higher doses.