Sisters (1973)

In Brian De Palma's Hitchcock-like suspense horror thriller with a Bernard Herrmann score:

• the opening shots of a fetus during the title credits
• the dual, Siamese twin characters -- French-Canadian fashion model Danielle/Dominique Breton (both portrayed by Margot Kidder) - one being a murderous psychopath - and a birthday cake inscribed with both of their names, bought by "colored" TV game-show player and advertising salesman Philip Woode (Lisle Wilson) who had just had a one-night stand with Danielle in her fold-out living-room sofabed in her Staten Island apartment
• the split-screen scene of a nosy and crusading reporter Grace Collier (Jennifer Salt) in an Rear-Window-ish apartment across the way witnessing the brutal stabbing murder of Philip by the deranged twin during a birthday celebration