In a Flash Back story in Elf Quest, Eyes High dies from blood loss shortly after giving birth to Skywise... plus losing her lifemate and almost being sacrificed by a human tribe, all due to a prank by two of the tribe's boys that went horribly wrong.
In Smax it's eventually revealed that Smax's mother died this way. She was raped by an ogre, who kept her in his cave and beat her, meaning she was in no condition to give birth when she did. Still, she was tough and she might've survived the birth... if she didn't have twins.
In the DC Universe, the mother of Cameron Mahkent, the Icicle, froze to death giving birth to him—not unlike the goddess Izanami.
In the Mirage Teenage Mutant Ninja Turtles continuity, Casey Jones' first wife Gabrielle dies due to complications while giving birth to her daughter, Shadow.
In the Little Victory universe, the birth of supers, at least those of 'Pantheon Class' power, is acompanied by a burst of power that not only kills the mother, but anybody else in the near vicinity.
Inverted in Strikeforce Morituri with Aline "Blackthorn" Pagrovna. As a subject of the Morituri Process, she should die within a year after acquiring super-powers. Instead, her pregnancy keeps her alive for several months afterward, and she dies soon after the baby is born.
This is part of the origin of the Johann "Red Skull" Schmidt, his mother died giving birth to him and his father hatefully tried to murder him right there and then until stopped by the attending doctor. With that kind of beginning, Schmidt only sank further.
This is one of the reasons Dupli-Kate and her twin brother Multi-Paul in Invincible have their multiplying powers. A bizarre curse on their family doomed their father to have so many children that he would be driven insane. Since their mother died in childbirth and he never remarried, it seemed like the curse would be averted. The curse got creative and gave Kate and Paul their powers, and their father did indeed go insane trying to handle the bizarre situation.
Madeline "Miss America" Joyce fell victim to this. More exactly, she died of complications stemming from childbirth with her and Robert "Whizzer" Frank's second, stillborn child due to radiation poisoning from her first offspring (Robert Frank Jr. aka Nuklo) while at Wundagore Mountain, Transia.
