By asking important questions like this one and staying as informed as possible, you are well on your way to increasing your chances of having a healthy pregnancy. The best type of physician to to consult with about this issue is an OBGYN. As you know it is important for your health to have an appropriate level of thyroid hormone. Your TSH level is the most sensitive measure of your thyroid needs. Having too much or too little thyroid hormone levels can be bad for your pregnancy. In addition, your metabolic needs will change with your pregnancy possibly changing the amount of thyroid hormone needed by the body. Your TSH level will change if the thyroid hormone you are taking is too much or too little for your body's need. I suggest that you schedule an appointment with your OBGYN that you will use for your pregnancy. Ask him or her how often you should routinely have your TSH checked. This will depend partially on how difficult your thyroid function has been to control, and what type of hypothyroidism you have. Of course if you have any change in your symptoms, you should inform your doctor
right away. Good luck with your pregnancy.