I have had 2 different REs prescribe me letrozole. I am on my second cycle to letrozole. I just had my cycle day 12 ultrasound, but only had a 12 by 8mm follicle and a thin lining at 5mm. However, back in the fall I had more positive results on letrozole. Today, the RE nurse said that my follicle could still grow. They did lab work and are going to call me in the afternoon with the plan.
I initially was very worried about the birth defect study. This article may shed some light on it for you (I attached the link below). I was so worried back in the fall that I called a woman who is an OB that I used to nanny for to double check what my RE had prescribe. She did not have any concerns about the letrozole since I told her I was definitely not pregnant. This still did not put my mind at ease so I called my best friend’s husband who is a pharmacist. He looked up the drug info and had positive things to say about it. Basically, my understanding is that if you are pregnant then you should not take it under any circumstance. However, if you are TTC it is fine to take because it has a short half-life so it is out of your system by the time you conceive. Clomid has a much longer half life and is still in your system when you conceive. Also, when I looked at a different article it said the birth defect rate for women who conceive by using letrozole is within the normal range (meaning same as the general population).
I totally understand being worried though. I was very concerned as well. This process is so stressful and then to think you are taking a drug that could cause birth defects is horrifying. Letrozole has positive things too because it does not thin your lining (clomid can thin the lining so that even if an egg is fertilized then it is not able to implant in the uterine lining…aka a chemical pregnancy). If you and your husband are nervous, I would ask to speak to the doctor or RE nurse about your concerns. That is your right as a patient.
I wish you the best of luck!!! I hope this information helps put your mind at ease. Keep my posted!
Femara or Letrozole, Fertility Drugs for Ovulation and Pregnancy