Dave has become a fetus inside his mom's womb and all of the warm liquid fills in and the birth canal closed shut. When he is inside her womb, his body starts regressing fast again.
His current age is 9 months in the womb. And now he is about to meet his limits as he turns into a 8 month fetus and then 7... 6... 5... 4. His arms and legs are losing movement, his heartbeat beating slowly and slowly, his brain about to not think nor dream, his eyes completely shut, his body about to deform into an egg cell.
Later, Dave is now an egg cell floating in his mom's uterus. Now the final phase of regression as the sperm is being pulled out from the egg cell. He joins with the other sperms as it swims backwards.
At the same time outside, Dave's Mom moans loudly as she is about to release something from her vagina. Then the vagina oozes out sperms. The sperms are none other than what it remains of Dave. Dave had reached his limits now that he is a pile of sperms.