Safety of thyroid medicines in pregnancy & its effect on baby -Dr. Beena Jeysingh HD

Overt and untreated hypothyroidism has been related to maternal and fetal complications.. likewise hypothyroidism has also been associated with maternal and fetal complications so if it is very essential to maintain the thyroid hormones within the normal limits as per the guidelines. So in a woman who is pregnant with hypothyroidism and hyprthyroidism, we have to give them thyroid replacement drugs and antithyroid drugs. So how safe are these drugs, with respect to hypothyroidism the medication guidelines currently states that the safest thyroid replacement drug is the oral levothyroxine, active T3 and dessciated thyroid are not advised. Iodine is also an important mineral required during pregnancy and lactation. According to WHO guidelines is about 250 micrograms per day and if a replacement is required, it is given in the form of potassium iodide. In case of hyperthyroidism, it is a little tricky situation because pregnancy complicating hyperthyroidisms management is more challenging than vice versa. Form 20 weeks of pregnancy, the fetal thyroid is very sensitive and completely responsive to the maternal antithyroid drugs and beta blockers that are given to treat the condition of hyperthyroidism because these drugs readily cross the placenta. So to keep in these antithyroid drugs in the lowest minimum dosage, is very important. We have two commonly used drugs, one is propylthiouracil and another is methimazole. Methimazole is always preferred over propylthiouracil because propylthiouracil has always been associated with maternal hepatotoxocty, that is maternal liver damage. But there is a constraint with methimazole. Methimazole is associated with congenital defect namely oesophageal and coanal atresia in the fetus. So considering these two we now prefer to give propylthiouracil during the first 3 months of pregnancy, that is the first trimester and then switch over to methimazole throughout the pregnancy. So what the complications related to thyroid dysfunctions. So what are they? Hypothyroidism to start off with, especially overt and untreated hypothyroidism has been associated with intellectual and neurocognitive developmental disorder in the fetus as well as with recurrent miscarriages and prematurity. Subclinical Hypothyroidism has no clear correlation with intellectual associated with low IQ babies with hypothyroidism it has been linked to early pregnancy losses, development of pregnancy induced hypertension or preeclampsia in the mother causing what us called as the thyroid storm, that is an acute and sudden release of gush of thyroid hormones, congestive cardiac failure in the mother and neonatal hyperthyroidism in the newborn.