The Great Lie (1941)

Sandra (Mary Astor) and Pete (George Brent) elope, but their marriage is invalid as she's not yet divorced. Sandra is, however, pregnant by Pete. Pete marries his former fiancée Maggie (Bette Davis), then flies to South America where his plane crashes. Maggie pays Sandra to let her adopt Pete's baby. Pete returns "from the dead". Sandra and Maggie contend for Pete and the baby.