Tsh levels low in pregnancy?

I don't know a lot on this. But my dr called and I have to go to an appointment for my low tsh levels. I haven't had this before in my previous pregnancies. So I'm actually nervous and scared at the same time. Have any ladies had this? How do they treat it? Will this affect my baby? And any information you ladies know I'll take it into consideration. I'm just scared and hope everything is going to be okay. Thank you