Mia Farrow, a popular actress, helped to popularize the pixie cut. The pixie cut represented freedom, and allowed women to be feminine without having the obvious long hair. In a way, the pixie cut was almost rebelling against the standards that women were held to. The pixie cut showed that women had the power to do whatever they wanted with their hair, and they could even make it "boyshort".
Fashion plays a huge role in Rosemary's Baby. Mia Farrow's baby-doll dresses, peter pan collars, bowler hats, ruffled nightgowns, and gamine hair cut all define her as child-like, gullible, and innocent...and add to the ultimate horror.