Contact them or don't?

For the past couple of months the pregnant SO has been very distant and not wanting to see much of her man and he has shown frustration towards this and makes her not want to be with him more. The guy keeps expressing his feelings towards the time apart that is breaking the relationship apart. Even though the relationship hasn't been a very long one, there has been a lot of passion and love between them. What is the best advice for the guy who is having so much trouble this to get his girl back? Should he continue to be sweet and loving with no reciprocation or should he give her space without much contact to have her come to him?