I watched this anime film on tv around 15 years ago, but it is probably older. It was in japanese with sub in my native language. There were few factions fighting each other and one of them tried to create new hybrid race. Those that were trying to create new race could have been an advence robots. Most of the fights are happening in space, between these advance robot aliens and girls who use mecha-robots to defend them self. Heres a little problem, there might have been one more faction, but im not completely sure...
As for as i can remember plot goes something like this:
There is a ship on which group of girls is traveling. At some point those evil robots/aliens attack the girls and battle begins. In order to defend her friends who are inside a ship, one of the girls uses her mecha-robot to fight those aliens. As the fight was going on outside, evil aliens send some missile that penetrates the ship. From that missile slime/water like creature appear and starts looking for girls.
One of those girls (i think she had short black hair) gets swallowed by that slime/water like creature. While inside of it, she had problem breathing and it looked like creature put something in her. After few moments her friends come to the rescue. Girl that was fighting outside dies and fighting ended.
Thanks to the sacrifice of their friend, other girls manage to escape. Somewhere along the way, girl who was swallowed starts experiencing a pain. After scanning her body they find out that she is pregnant. Not long after they land on some earth like planet. After landing they start planting some traps/bombs in case those aliens show up.
Here she gives birth to a baby boy. I remember that little boy starts slowly walking and leaves the room, short girl (i think she had blonde hair) who was supposed to keep an eye on him notices that he is missing and goes after him. Along the way he starts growing and in one point he jumps in the lake. Girl tries to follow him and she does the same. By the time they both reached other side of the lake he is fully grown and helps her to get out.
While this is happening his mother and another girl are fighting aliens that came to take that boy i think. In the end, those traps/bombs that they planted begin to detonate one after the other. In same time, short girl and now fully grown man are launched in space so they could survive. Girls that were fighting and all the aliens end up dying from the heat blast that those detonations caused.
From their escape pod/rocket in space, man and girl can see how planet turns into something that resembles the sun. Last scene is slowly shifting from planet that turned into sun to one where rocket is heading. Planet they are heading to is earth and those two last survivors represent Adam and Eve (maybe).
I would like to thank ConMan for his suggestions on how to improve this post and Nathan for fixing it :P.