This is one of those films which really shouldn't work, but somehow does.
Arnie plays a doctor who, along with his work partner Danny DeVito, has created a drug to reduce miscarriage risk. After being denied the chance to conduct human experiments, the two then cook up the idea of getting Arnie pregnant & trying out the drug on him.
Everyone in the film is incredibly game and keeps a relatively straight face during this farce. It does stretch credulity at times, but never loses its fun side. There are also some quite profound questions about fatherhood & the difficulties of pregnancy.
But I will end by saying that like with many other films, in our current world, there is absolutely no way this film would ever get made today. The outrage machine which is the extremely vocal group of hyper sensitive individuals in the world today would have a collective meltdown if a film in which a man who gets pregnant and is mocked & made fun of for entertainment was released.