Lets see
1) Annie from the Jet mission you can knock up but it isn't 100%
2) Amy from the storyline you can knock up
3) Tom's mother you can knock up with your kid (100% here)
4) The Asain girl you save should you choose Chang's mafia but it isn't 100%
I only remember Amy, are there mentions of it with Annie, the Asian girl, and Tom's mom (name?)?