I think that the best part of this movie is that is was made completely straight. It's like no one involved was aware of how ridiculous the whole story is. It seems that back in the early to mid '70s, the trend for horror films was demonic possession. In this film, you have Lucy (Joan Collins) who has just given birth. Prior to her marriage and pregnancy, she had been some sort of dancer. I'm not quite clear if she was a stripper. I say this because while other dancers who worked for the same employer were clearly strippers, Joan is clothed and does a routine with a dwarf named Hercules in the one dance we see her do. Anyhow, after her last performance, Hercules decides to get all touchy-feely with Lucy but she's not interested. Instead, she beds Tommy, the club's manager. As she and Tommy leave the club, Hercules curses Lucy and says she will have baby who will be possessed by the devil. So, ok, you've got the set up. The baby is born, he grows rapidly (I guess...he didn't seem that big to me) and then starts to kills just about everyone who gets near him. Oh yeah, Lucy is married to Gino, whose sister, Albana, is an actual Catholic sister. There are all sorts of unanswered questions, some of which the movie proposes and some of which a viewer might have. For example, sometimes Lucy looks at the baby and sees Hercules, so...is Hercules demonic? Is it Lucy's imagination? Does the baby turn into Hercules when he kills people? How does Hercules have the power to curse or possess a baby? See, eventually, Albana attempts an exorcism, which has an affect on Hercules, but between his curse and the exorcism, Hercules is largely absent from the film, except when Lucy looks at the baby and sees his face. So, is Hercules a demon himself, or is he engaged in some kind of witchcraft? I don't know. Then, there is also the question of the baby's parentage, which the movie raises but never answers. See, the night before Lucy and Gino wed, Lucy slept with Tommy again and nine months later, the little devil was born. So, is Gino the father? Is Tommy? And then there is this idea that the baby "doesn't want to be born", which is just odd. The nurse mentions that when the baby is born and then later, Lucy shouts "I know you didn't want to be born" at the baby as he's attacking her but it's just this idea that's thrown out there without anything to back it up. I mean, the baby seems to be enjoying himself, killing at will. But then again, if Hercules is doing all this, is Lucy yelling that at him? Why wouldn't he want to be born? Because he's a dwarf? Because she rejected his advances? That's awfully presumptuous, Lucy!
This movie is totally laughable and the only way to enjoy it is to not even attempt to take it seriously. As mentioned earlier, you've got Joan Collins, who was like 42 when this was made and is looking pretty fabulous (although the other reviewer who mentioned the "gratituous nude shots of her mostly naked" might be overselling it a bit), plus movie fans will probably recognize other notable faces like Donald Pleasance, Ralph Bates, Eileen Atkins, and one-time Bond girl Caroline Munro. They all come together in this mess and try to sell it as something worthy of being mentioned in the same company as "The Exorcist" and "Rosemary's Baby" or even "The Omen" (which came out after this) but it totally falls into the "so bad it's good" camp.
This movie is also known by the titles of "I Don't Want To Be Born" and "Sharon's Baby" (which is weird because there is no one named Sharon in the movie).