C.C.
I went on Zoloft while I was pregnant with my second child. I had had horrible PPD after my first baby was born, and the pattern was starting to happen again. I spoke with my OB at some length about it, and he assured me that the use of anti-depressants has been well studied and is generally quite safe for the mother and baby during pregnancy and nursing. I felt SO much better on the anti-depressants, I can't even tell you. Without them, I cried several times a day and in general felt awful. With them, I felt like my usual self - cheerful, happy, and able to deal with life.
My younger daughter turned out great, and we were able to bond so much faster than I had with my first daughter. I think depression suppresses your ability to make oxytocin, which is what allows you to bond with and love your baby. So my vote - if the anti-depressants are working for you, don't stop taking them.
Best of luck!