I never cease to be amazed by some men's insistence that having sex *provided to* them by another human being, willing or not, is some kind of divine right.

Your wife said NO. Whatever the reason, talking about it in an adult, non-judgemental and non-pressuring way is the first course of action, wherein you assure her that you value all of the sacrifices she's making for you and your baby (A HUMAN GROWING IN HER BODY, putting her life and body at risk!!), and if she doesn't want to have sex, what IS she comfortable with (holding? does her body pain, then holding is out. Kissing? Etc. etc.), you assure her that you still love her just as much (assuming that is true. If it isn't, then why are you married and reproducing?). Then you tell her to let you know when she's ready for sex being done to her body again, and you go to the bathroom and re-acquaint yourself with Mrs. Palm and her 5 daughters at your leisure and convenience.

You do NOT pressure her to have sex she doesn't want by saying you'll go to someone else for sex or she must make some plan to provide you with sex. SHE IS NOT RESPONSIBLE FOR PROVIDING YOU WITH SEXUAL RELEASE! That is what's called coercion, and coerced sex is rape, even if you are married, whether she is pregnant or not.