I have just started by follicular study since 2 months. The first month showed very slow growth of the follicles, for which my gynecologist prescribed Fertyl. Post taking that, my follicles for this cycle has been very good. My doctor wants it to reach 19-20mm and then give me an injection to rupture it. Can anyone tell me what is this injection, where is it administered and what can possible side effects be?

Need a reply as soon as possible, because I think she'll be administering it within the next 3-4 days.