Bart: Kids don't die!
In most fiction, innocent characters (babies, children, dogs) sit very high on the Sorting Algorithm of Mortality. They tend to make it out of dangerous situations unharmed while many adult characters in these same situations do not.
No matter how bad the villain is, he will stop short of killing a child. Even natural disasters seem to avoid killing infants and dogs. Something about a baby or puppy makes you stop, think twice, and show a last flicker of compassion. Those who don't have that last drop of humanity in them will generally be stopped some other way.
Of course, this only protects against killing them off on screen; destroying a city in a fiery conflagration and killing the no doubt tens or hundreds of thousands of babies therein is A-OK, because A Million Is a Statistic and the audience won't see them.
This trope extends to just about anyone conventionally considered inherently "innocent," and can therefore sometimes reach out to cover the mentally handicapped. Whether or not this extends to pregnant women is a toss-up; fetuses have more relative protection than dogs, but less than already-born infants. Except in series where Status Quo Is God, because then the Convenient Miscarriage will rear its ugly head.
Note that this doesn't seem to apply to the Enfant Terrible, who dies horribly in all manner of works.
DO NOT list "aversions". Those go in Child Characters Dying.