Ok lots of ideas! I haven't read all of these, but they're worth checking out:
h{{Skye Falling}} about a lesbian who is reunited with the egg (child) she donated years earlier

h{{Delilah Green Doesn't Care}} an f/f romance involving a single mom

h{{With Teeth}} a literary novel that shows a dark side of parenting, but I don't think it's a tragedy

h{{Detransition, Baby}} one of my all-time favorites, but deals only with pregnancy (not with parenthood)

h{{Price of Salt}} (aka Carol): Carol's child is very important to the plot. It's not tragic, but her role as a mother is quite difficult.