I sent an email to a professor in my university two months ago for a research position in the lab since her research was about my place and interests.She told she will contact me sometime in feb (since she was on a maternity leave till December and has joined again in January).How should I remind her gently about my email or should I wait till the end of the month?
Maternity does rearrange your life quite a bit, I'm not surprised this fell in a crack somewhere. First make sure she is back, and how all went with the baby (there can be serious complications, and she might not be back yet).
Send a short mail asking if the position is still open, reminding your earlier contact, and perhaps attach whatever you sent originally. Remember to congratulate on the new baby.
Simple! Forward the same email to the professor, and let him/her know if he/she has any update on the position. Then the professor can catch up with the last email you sent by scrolling down to this forwarded email.
There is another way in which you can go yourself in person and ask her whether that particular position is still vacant or not. In that way you can remind her that you had applied for the post.