Hello, I really appreciate your concern. Spotting is common during early pregnancy. If there is more bleeding then it could be due to progesterone deficiency. Thyroid hormone deficiency could be the cause of spotting. You have not mentioned about previous TSH level of your wife. Tell your doctor about hypothyroidism if you haven t done yet. Dose of levothyroxine should be increased accordingly to accommodate the increase in thyroid hormone replacement required during pregnancy. You should continue to monitor your thyroid function tests every 4-6 weeks during pregnancy. Because the iron and calcium in prenatal vitamins may block the absorption of thyroid hormone in your body, you should not take your prenatal vitamin within 3-4 hours of taking levothyroxine. Untreated or uncontrolled hypothyroidism can be associated with missed abortion or spontaneous abortion during pregnancy. It also leads to maternal complications of pregnancy like eclampsia, maternal hemorrhage etc. It leads to delayed brain development in the baby. Hope my answer has solved your query. Take Care. Thank you.