So we know that Holloway and shaw have some sort of relationship in this film. We see the lead up to them doing the business. Now in all of the threads i've seen i can't recall this being brought up.
From the latest trailers we can see that there is something in holloways eye thats moving like a worm. What if he sleeps with Shaw then wakes up to find out that he has some sort of infection (the mirror scene) which impregnates Shaw. Which leads to Shaw becoming "pregnant" with this weird hybrid creature thing