What are the effects of hyperthyroidism on pregnancy?

Several. May make your pulse go up. May make your nausea and morning sickness worse. May cause problems with your metabolism and growth of the baby.
Bad news. Hyperthyroidism makes it difficult to become pregnant in the first place. If you do become pregnant while you're hyperthyroid (or the other way around) it definitely will increase you chances of miscarriage and fetal loss, plus potential thyroid problems in the fetus/baby. Make sure you see your endocrinologist immediately and the thyroid is kept in control, which will lower your risks.