Nasce um Monstro (1974) was filmed and edited simultaneously with another Larry Cohen film, Inferno No Harlem (1973), which was shot on the weekends during the production of Nasce um Monstro (1974). This means that many of the same cast and crew put in consecutive seven-day work weeks to create both of these films.
For close-up shots, Rick Baker created a full-head monster baby mask, a pair of gloves and a partial body suit, which were worn by Baker's then-girlfriend and later wife Elaine Alexander.
Larry Cohen called Rick Baker on the telephone while Baker was at the home of Dick Smith where he was working on the special effects for the film O Exorcista (1973). During that initial phone call, Cohen pitched the film's concept to Baker, and suggested building a monster baby suit that could be worn by Cohen's cat, or "a chicken or something [...] maybe two chickens!"
Larry Cohen originally planned to cast Anthony Perkins and Janet Leigh in the lead roles, thereby creating a mini-Psicose (1960) reunion.
This film was first released in 1974 with a lackluster advertising campaign and was unsuccessful at the box office as a result. Later someone in charge must have thought that it had untapped potential as it was re-released in 1976. This time, it had the iconic advertising campaign of the darkly lit baby carriage with a hand with clawed fingers hanging over the edge for the print ads and TV commercials. The TV commercials also had the ominous narration and the music imitating a heartbeat that struck terror into many a 1970s kid who would have encountered the ad during their favorite TV shows and films. Naturally, this time it became a hit and spawned two sequels and a remake.