Neglecting babies in The Sims 4 doesn't result in their death, your kids just get taken away by child protective services. While grim, activating CPS has become its own category of speedrun now.
The current record holder, SimplySeze, managed this depressing task in about fifteen and a half minutes. The entire speedrun requires you to meet another sim, be impregnated by them, have the baby, and then have the baby taken away.
The key, after you impregnate your sim, is to get them to sleep as much as possible, which sets the game in a super fast forward. The sim will get through the pregnancy and their child's life in a matter of minutes. There's three different speedruns in her video, and the CPS one starts at 3:12.
SimplySeze's commentary is totally hilarious. After she manages to get her sim pregnant and gets close to her giving birth, she says, "Almost in the third trimester guys. Then we just need to have this baby and ignore it." She also notes how tricky it is to take care of a sim's needs while trying to keep them asleep most of the time.
"I almost had a sim die of fun deprivation in a speedrun yesterday because I wasn't paying attention to their needs." Still she manages to get her sim kid taken away, noting that it happened a lot faster than she expected. Congratulations?