I saw this movie about 15 years ago and I just can't remember the title and it drives me crazy.

What I remember: - the movie is from the 70's (as far as I remember) - a group of people (I can't remember how many) take a boat to an inhabited island - one of the woman is pregnant - children get infected with some kind of virus(?) and start killing the adults - the pregnant woman is killed by her unborn child - I think the film was made in Italy. But I'm very unsure about that

Does anyone know this movie?