It Lives Again (1978)
So maybe the premise -- mutant babies with super-intelligence, super-strength, claws, sharp teeth and a penchant for overreaction -- is kind of silly and maybe the babies look like rubber blobs with a few pointy barbs the few times they are shown, but It Lives Again is actually a very good movie.
Made by Larry Cohen, who was also responsible for films such as It's Alive (apparently this film's prequel), Uncle Sam and Q: The Winged Serpent. It Lives Again features great performances, suspense, scares, atmosphere, and a script that draws you in and won't let go from the first masterful opening scene. Imagine what it could have done with a less silly premise and a real special effects budget.
The plot, which is intelligent considering what it has to work with, although it probably would make more sense if one had seen the prequel, concerns a string of mutations (I've gathered from the synopses I've seen that the mutations are being caused by some environmental problem - presumably this was more explicit in the first film) that are randomly occurring with various babies. The government and medical establishment know enough about this (which is seen by some as a continuation of evolitionary "progress," by the way) that they've been able to determine which babies are at "risk" through pre-natal testing. Deeply involved with current pregnancies, deliveries and executions, but on different sides of the fence, are former parents of mutants. The conflict here comes from a small group of pro-mutants trying to protect Eugene and Jody Scott's (Frederic Forrest and Kathleen Lloyd) kid from immediate extinction by an the anti-mutant establishment.
There are obvious references to the abortion dilemma here, and Cohen does a wonderful job in relaying the complexities involved with "playing God" and deciding whether one has a right to terminate human life under certain criteria.
Also of note, Bernard Herrmann supplied the score, which is functional but unfortunately a disappointment considering his track record, and Rick Baker, amazingly enough, is the man responsible for the rubber babies (he was one of the special effects/make-up people behind Star Wars, Men In Black, The Nutty Professor and Batman Forever).