Indeed this is something i discussed before..
Shaws Pregnancy came from one of TWO ways.
1) Black Goo that Holloway had, mutated his Sperm that then infected Shaws Egg.
2) Black Goo (Top half of the vials) contains a Parasitic Worm that like a Virus or Sexually Transmitted Disease was passed onto Shaw via Sexual Intercourse.
Shaw as a Mammal, once she is pregnant she cant become pregnant again until after the birth of her Child.
So it depends on the life span of any Mutated Sperm, or Parasitic Worms... if these can survive for days, then yes after her C-Section one of these could then get her Pregnant again.
If option 2) is what happened then this leaves David able to do the same experiment again, if all Holloway was is a means to pass on the Parasitic Worms to Shaw.
David would have to then find some other more invasive methods... "Big Things have Small Beginnings" and all LOL
But yes if either if the above applies then yes she could still get pregnant again, and if its number 2) then David can perform this at any time of his choosing.