Straight out of the pussy, the baby attacks and kills (off screen) five people in the delivery room. After that it crawls all around Los Angeles killing people off screen. The dad is fired from his job for having a "retarded" baby and the police are running around like a bunch of bloodthirsty maniacs. Which raises the question: since the police know that the baby kills with its claws and teeth, then why do they only wear their normal street clothes? If somebody ordered me to go in a building to confront the killer baby I'd be decked out like the fuckin' bomb squad!
Anyway. The story sounds exciting, but it's not. In fact, it's extremely boring and while audiences back in 1974 might have got a kick out of it (did they?) people nowadays would probably be bored stiff by the slow story, lack of violence, amateur acting, weak script and terrible lighting.
Not the worst thing I've ever seen, but I was severely disappointed by how lackluster the whole thing was. Skip it.
Part 2 - It Lives Again (1978)
Part 3 - It's Alive III: Island of the Alive (1987)
Remake - It's Alive (2008)
The same weird wallpaper appears in Part 3.