From this site...which sheds light on bad moms and bad boyfriends
http://fathersforlife.org/articles/report/resptojw.htm
PERPETRATOR RELATIONSHIP [3]
31.5% Female Parent Only
10.7% Male Parent Only *
21.3% Both Parents *
16.3% Female Parent and Other
1.1% Male Parent and Other *
4.5% Family Relative
6.1% Substitute Care Provider(s)
5.7% Other
2.7% Unknown
* “Male parent” in that context most likely is just about anything but a natural father.
However, thinking further about it, I'm less surprised. Not because of abuse cases, but insurance money and "getting rid of burdens". Diane Downs type of situations.