My book from the Dr says it starts at 25 weeks also. But like she said ^^ I just divided the time up by thirds. So I'm going to go with 27-28 weeks.
I believe it's 27 weeks... I just break up the 40 weeks into 3 segments... idk...LOL
My doctors and all of my books say 28 weeks. There are so many different opinions about it. I just go with 28 weeks.