Hello, I Am 4 Weeks Pregnant Through IVF Cycle. I

Hello, I am 4 weeks pregnant through IVF cycle. I have been taking Progesterone in Oil. My doctor recommended I start taking the estrogen patch to increase my estrogen levels. The pharmacist said it is tetrogenic drug as well as Progesterone in Oil. I am so worried I am doing harm to my baby. I am so conflicted on how I should proceed. Why would they prescribe a teterogenic that has a risk of causing birth defects? Any insight would be much appreciated. Thank you.