Is it true that every man cheats on his wife or girlfriend when she is pregnant?

NO! Several men are despicable like that, but believe it or not, there are many decent husbands out there who can wait nine months for their wife!

I agree with the above contributor 100%. I might also add, that sexual relations between husband and wife do not stop when she is pregnant. Most will continue until the third trimester; just not as aggressively. Whoever gave you that information is evidently a very uninformed individual.