Empty Cradle(1993)

Jane Morgan gives birth to her baby at the hospital. When she wakes up the next morning, the hospital tells her, that her son died at birth. However from ultrasound reading she had before, she knew she was having a girl. Now the hospital is stone-walling her, saying she is just in denial, due to her loss. Now she is trying to fight the system, to find evidence of the apparent mistake by the hospital. Only it wasn't the hospital's mistake. Nurse Rita Donohue is the one who made the switch. She faked a pregnancy to hang on to her roving boyfriend. But she grabbed the wrong baby, her boyfriend wants a son, so now she's faking a second pregnancy, and making plans to get another baby.