Wait. this actually adds up!
This thread's OP:
http://uboachan.net/t/res/1891.xhtml
theoritized that Kasei-san (the martian creature) might be Madotsuki's unborn fetus, which makes a lot of sense when taking in account the "barren" planet in which it is located. And from this very thread, I quote: "Takofuusen is Masada's spaceship".
So, according to this, it's not hard to arrive at the conclusion that Madotsuki had been pregnant before, almost certainly carrying Masada's baby twins, which unfortunately turned out to have that same complication, resulting in a miscarriage, possibly symbolized by the spaceship's "crash".
This would also explain why Kasei-san changes its eye color when stabbed (one color for each twin), and would most certainly be able to explain the numerous depictions of decapitated pregnant monsters throughout the game, as her self-blame and loathing led her to despise herself for what had happened.
Sounds pretty good, doesn't it?