According to Carl's guide, the "determine gender" option is available at Medical career level 10, according to Sims Wiki it's at level 8. My dilemma is that the option in available right away with Geoffrey Landgraab in SV and he starts at level 7.
Anyway, here's my list of Medical career Sims.
Sunset Valley: Jamie Jolina, Lvl 6 // Geoffrey landgraab, Lvl 7 // Morgana Wollf, Lvl 5 // Madison VanWatson, Lvl 1 // Dustin Langerak, Lvl 1
Riverview: Jebidiah Wilson, Lvl 5 // Shirley Lin, Lvl 5 // Marisol Lobos, Lvl 4 // Don Lothario, Lvl 1
Twinbrook: Nick Knack, Lvl 6 // Shamus Drudge, Lvl 5 // Molly Coddle, Lvl 1
I'm not sure at what level Doctors can determine the gender of an unborn Sim, but there's the list.