Sometimes, the actions are driven by the prospect of insurance money. In the case of Charles Stuart, a Massachusetts man who killed his pregnant wife in 1989 and committed suicide before he could be formally charged, his younger brother claimed he wanted the insurance money. But some argue that money motives can be overstated in these cases.
"Sometimes the husband or boyfriend can feel the stress of having a family, like they can't afford to have a baby right now and a family," said Burke. "A lot is made about insurance policies being taken out at the time, but really, taking out an insurance policy during pregnancy would be the time to do it. When it's just the two of you and you're young, you feel invincible. But when you have a child on the way, you begin to think about, 'What happens if something happens to me? How will my child be taken care of?' "
Arguably, there's not much expectant mothers can do to prevent random attacks from women who want to steal their child. Brady, who said maternal instinct made her fight to save herself and the daughter she gave birth to last week, was lucky when she managed to ward off her attacker.
But some experts say there is something women can do to protect themselves from male assailants during pregnancy: At the very start, they should be wary of the men they become intimate with. Controlling behavior should be seen as a warning sign.
"Be careful about who you decide you're going to have children with. Be careful about the person you decide to make long-term decisions with," Brown said. "Sometimes we, as women, don't make the best decisions about the people we decide to have a child with or rush into a relationship too quickly and get pregnant too quickly."