As any true Charmed fan knows, Phoebe foresaw her daughter P.J several times before her birth. The first time being when Phoebe was on a Vision Quest at Magic School. But... was that really P.J. that she foresaw during the Vision Quest. According to this very wiki the time line would place the pregnancy that Phoebe saw at some point between 2008-2009. Which means that it couldn't have been P.J. that she was pregnant with, as P.J. was born in 2007. If she had been pregnant with P.J. either one of two things should have been different. Either A) she should have seen that both her sisters were pregnant as well, since their daughters were all born in 2007 OR B) Considering that her daughter was born last she should have been much farther along in her pregnancy.
But we did not see either of those things. So I have another theory. I think that when Phoebe went on her Vision Quest she actually saw herself pregnant with her second daughter Parker who was born in 2009 therefore Phoebe would have been pregnant with her some time between 2008-2009.
If you think about it, it lines up perfectly with the timeline of the Comics.