Baby Blood (1990)

Alain Robak’s Baby Blood is a French cult horror classic that dives into extreme body horror and surreal splatter. When a parasitic creature invades a young woman’s body, she is driven to murder in order to feed it — a grotesque and shocking blend of gore, surrealism, and feminist undertones. Widely regarded as one of the defining European splatter horrors of the 1990s, it has maintained strong cult status among genre fans.

Från IMDB:
When a strange creature crawls into a woman's uterus she becomes a killer in order to feed the tiny terror growing within her.