That last one is a biggie. Having a baby can trigger unexpectedly negative emotions in a woman's partner (from anger to jealousy to the accusation that he's "being trapped"). Those emotions can play out brutally against the mother and her unborn baby.
A 2011 NIH study found that pregnancy-associated homicide claimed more lives than many obstetric complications, including hemorrhage and preeclampsia ---and that husbands and/or boyfriends were linked to nearly half of those deaths.
Those are all connected to the comment I made above.
...and domestic violence.
Yes,domestic violence can be a factor. And that goes to upbringing...boys who are taught that it's OK to beat your wife and girls that are taught to expect abuse as adults.