Thyroid produces two hormones. They are thyroxine and triiodothyronine. They are responsible for metabolism in body and metabolism in turn is responsible for affecting each and every function body carries out. Thyroid thus can also affect ovulation process in females and thus it is seen that women affecting from thyroid disorders show various difficulties in conceiving as well as complications in delivery of child if they conceive.
Irregularity in periods is due to imbalance in thyroid hormone. Too much production of thyroid hormone by thyroid gland which is also known as hyperthyroidism as well as too little production of thyroid hormone by thyroid gland also known as hypothyroidism both are responsible for creating irregularity in menstrual cycle. This is thereby responsible for affecting ovulation cycle which will pose difficulty in conceiving.
In your case, you have mentioned that your periods are regular but bleeding continues for 11 to 15 days. The reason for prolonged bleeding is your thyroid disorder. Since your periods are regular and it may have helped your conceiving as regular periods are helpful in proper and regular ovulation cycle. Are you taking any medication for thyroid disorder. In your case, your medicine might have helped your conceiving. It has kept your thyroid hormone in normal range and thereby your other body functions like periods and ovulation cycle too became regular which in turn helped you in conceiving.
Though you have not mentioned, but I feel that you are affected from hypothyroidism. In hyperthyroidism, ovulation period or cycle is greatly affected and women suffering from it cannot conceive due to irregularity in menstrual cycle. However, in hypothyroidism ovulation occurs normally. Whatever may be the case, you need to consult doctor and take proper medication and treatments recommended. Early treatment decreases the risk of complications as well as severity.
These are the severe complications which women suffering from thyroid disorder experience.
2) Placental abruption,
3) Premature delivery,
4) Babies born are deficit of intellectual development,
6) Gestational diabetes,
7) Spontaneous labor,
8) Postpartum hemorrhage,
9) Still birth etc.....
Continue your pregnancy only after complete examination and if your doctor encourages you to continue it. Otherwise, you may risk both yours as well as your fetus life and thus consult your doctor at the earliest.