what I found interesting was the way, Sonia especially as a woman, was able to put aside her maternal instinct, because she knew it would not be beneficial for the child if she has chose to have one. Her job was too, demanding in itself that she would not have been able to give a child the time it needed and, so she made the choice to have a career instead of a family. Sonia also knew the dangers associated to her health, because of the diabetes and didn't know the longevity  of her life, but then again none of us do and tomorrow is never promised, so i personally believe the real reason she chose not to have a family was, because she wanted to be able to put 100% of herself in her career and nothing else.