According to The Washington Post, more than 1,300 pregnant women and new mothers have been slain since 1990. And a Maryland study published in 2001 in the Journal of the American Medical Association says a pregnant woman "is more likely to be a victim of homicide than to die of any other cause."
What's behind this?
Clinical psychologist Robert Butterworth tells The Early Show co-anchor Rene Syler the Underwood murders represent "one of those cases where pregnancy indicates a crisis point. We're seeing research around the country that actually shows that, if you're pregnant, the leading cause of death, sadly, is homicide.
"(It's) because pregnancy for relationships can be life-altering and by that I mean, financial responsibility. It can also mean, if the person's having an affair with the individual, that this can actually cause shame. So in a sense, somebody becomes pregnant, the woman has control over having the child or not, but the man has no control, and sometimes the man is kind of almost psychologically backed into the corner and as a result, sometimes homicide occurs."
Butterworth notes that, "Pregnancy used to be a deterrent. It doesn't seem to be a deterrent now. I think the fact is that, when you ask people what role will children have in their lives, a lot of people are not happy about pregnancy. And a lot of men become stressed when the individual becomes pregnant, either because of shame or because of not wanting the child or because the whole relationship changes and, sadly, murder and homicide become alternatives. We need to find some other way rather than taking this -- doing something as horrific as this act.
"We know men are becoming more violent. It's almost the profile of a white man in his '30s focused on guns and women that are in relationships where men are threatening and there's domestic violence and these things kind of add up.
"When a relationship is somewhat on the edge and a pregnancy occurs, that could kind of overwhelm the relationship to the point where the husband or the lover or the boyfriend cannot tolerate it and in (the Underwood) case, things just go to a head and things erupt and become out of control."
Are there warning signs women should watch for?
"Most people are killed by people they know. Most people are harmed by people who have made threats earlier on and, in a situation where you're in a relationship where you're frightened of the person that you're with, when a stress happens like a pregnancy, you really have to be careful, because the warning signs are there. People usually make threats of death or destruction."