that doesn't exactly excuse the baby morphing into a different species in the womb just because its mom turned into a vampire *after* conception.
Read it again slowly, notice the subtle differences between the number '1' and the number '2':
Sim 1 impregnated Sim 2. Just a few hours before Sim 2 went into labor, Sim 1 metamorphosed into a vampire.
It's worse, it's the dad that was changed into a vampire.