I'm still new to fish keeping. Because I had a hard time finding find good photos of fry / pregnant guppies, I took a series of photos of my last guppy's birthing. (I adjusted the color a bit.)
The gravid spot with fry eyes clearly visible. (4 days prior to birth)
Another image that shows fry eyes.
This shows how big she was 4 days prior to giving birth.
This shows the size difference. It also shows how flat her belly was after all the fry were born. Yes, she may have eaten a few, but if she did, it wasn't many.
Some of the fry would drop to the slits or slip all the way to the bottom of the breeder.
Some would immediately swim to the top to rest on the plants near the surface. Others would need that bit of rest before the swim to the surface.
As an experiment, I used a breeder this time. I added a few cuttings from plants in a well established tank. I haven't seen that anywhere else, but it seemed like a fine idea. The little ones really liked the plants. And the mother guppy would occasionally swim in and against it during the birth - I'm assuming contractions or something.
Without the breeder, I was "rescuing" about 10 - 15 fry. With the breeder there was maybe 35 - 40 fry. It was very hard to count them. I've lost a few in the weeks since, but I still have 30+.
Hope this helps others who are anxiously awaiting their first fry drop.