This is an old made for TV movie where there is a planet of all women and they board a ship and come to Earth. They all get in relationships with the men and become pregnant. All of them have female babies, because they can't make male babies. One day there is a sign and all of the women leave and get on the spaceship to go back to their planet, taking their children with them. One of the female aliens is an artist and covers one of her paintings and tells her husband that he cannot look at it "until the sky turns yerple" (? spelling). The sky turns a crazy purple color and he looks at the painting and then chases after his wife, but she gets into the spaceship and leaves.
"The Stranger Within"(1974 TV movie)?
It was written by Richard Matheson and it featured Barbara Eden as a woman who gets pregnant, even though her husband has a vasectomy. Below is the IMDb page.
Here is part of the plot synopsis from Wikipedia describing the climax to this movie. It matches your description of the ending you remember, but the alien baby is male?
"During the night, Ann sneaks out to an abandoned house in the woods, where she gives birth. She walks into the woods, where many other women are also walking with their alien babies. David looks at one of Ann's paintings, depicting the alien being's home planet. The painting starts to smoke. David looks out the window and screams Ann's name, as he watches a spacecraft take Ann to the alien's home planet."
Here is a scene from YouTube. Barbara Eden's character is showing signs that her baby is an alien.