Does Primulet N Cause Infertility?

Hi I was send to you to ask a question about Primolut N. Was prescribed it for mid cycle spotting but have just read about birth defects and infertility associated with use and that it can be used as a contraceptive. I've been trying to get pregnant for 23 months so this has come as a shock that I was prescribed this. My doctor knows all this so why would be prescribe a tablet so dangerous. I have to take it for 15 days a month for 3 months from cd11 to cd25. What should I do?