Uncontrolled hypothyroidism can have adverse consequences for both mother and child. Hypothyroidism increases the risk of hyperemesis, miscarriage, stillbirth, premature birth, placental abruption, low birth weight babies, postpartum hemorrhage and other complications. More seriously, hypothyroidism can affect the development of the fetal nervous system and bone growth, resulting in mental retardation and short stature of the offspring, commonly known as “cretinism”. Therefore, it is important to monitor maternal nail function before and during pregnancy and to provide timely and appropriate treatment. When a hypothyroid patient is pregnant, the following must be met 1. Hypothyroid patients should consider pregnancy only after their nail function (FT3, FT4, TSH) is normal. It should be emphasized that due to the physiological changes of pregnancy, the reference range of thyroid function indicators during pregnancy changes and pregnancy-specific reference ranges need to be adopted. The normal range of serum TSH in the general population is 0.3~5.0mU/L, while TSH should be controlled below 2.5mU/L during pregnancy, and FT4 should be kept at the upper 1/3 level of the normal range for non-pregnant women. 2, can not stop using hypothyroidism treatment drugs. Some hypothyroid patients stop their medication after pregnancy because they are worried about the adverse effects of taking thyroid hormones on the fetus, which is very wrong. Thyroid hormone is a physiological hormone that is essential to the development of the brain and bones of the fetus, and once lacking, it may cause “cretinism” in the offspring. As long as the replacement dose is appropriate, there is no adverse effect on the human body. 3. Be sure to have regular checkups during pregnancy. For patients with hypothyroidism combined with pregnancy, the body’s demand for thyroid hormone will change as the gestational weeks increase, so it is necessary to review the thyroid function regularly and adjust the replacement dose of thyroid hormone (i.e. L-T4) according to the TSH and FT4 levels to ensure the normal development of the fetus. 4. If a pregnant woman with hypothyroidism comes from an iodine-deficient area, the patient can consume iodized salt and iodized food. Thyroid tablets should be taken separately from iron, calcium and vitamins for at least 2 hours or more. 5. It is better to give birth in a general hospital, so that if there is any change in the condition, it will be easier to consult a specialist in time. Cord blood should be tested for thyroid function and antibodies (FT3, FT4, TSH, TGAb, TPOAb, etc.) at the time of delivery to keep track of the condition of the mother and baby, and to recheck the above items after the child is full term. As well as early screening and timely treatment of congenital hypothyroid children. 6.After delivery, we should continue to take medication and adjust the dose of medication in time according to the nail function examination. 7, after the birth of the fetus, we should also closely observe the daily life of the baby, if it appears drowsy, unresponsive, refuses to eat, etc., should promptly consult a doctor. 8. Pregnant women with hypothyroidism can breastfeed normally after delivery. Clinical practice proves that as long as the thyroid hormone level is controlled satisfactorily during pregnancy and the thyroid function is basically normal, the prognosis of mother and child is mostly good; otherwise, the complications of mother and child are significantly increased.