Can a second pregnancy be difficult for an Rh-negative mother?

Hello doctor,

My sister is five months pregnant. She had her anatomy scan recently, and she was told that baby is in between 1 to 3 percentile, and there is a problem with the placenta (they suspect the baby is not getting enough oxygen and nutrition). The genetic test they did before (harmony test) did not show any genetic disorder. Doctors told her they would check the growth of the baby in two weeks. Meanwhile, they did amniocentesis to confirm baby does not have a genetic disorder, and the results are pending. She was told that in such cases, the baby is so small she might die in the womb, which puts my sister's life at risk as well. Because my sister is Rh negative, and the baby is most probably positive (her husband is positive and does not have anyone Rh negative in his family). She was given an injection for Rh incompatibility. Currently, she is on Aspirin. My sister used IVF to become pregnant.

My questions are:

1) What are the chances of my sister dying if the baby dies in her womb?

2) If the baby shows growth after two weeks scan, what are the chances of being born with a neural or motor disorder?