Baby Monitor: Sound of Fear 1998 on netflix

A neglectful mother overhears her husband on the telephone at their workplace talking with their babysitter. She discovers they are having an affair and are going to have a baby. She concocts an evil plan to win back her husband and remove the girl and baby. Two men are hired to kill the girl and hold the son hostage in order for her to play the hero and reclaim her husband. The plan hits a snag when the criminals enter the wrong apartment.