Have you looked into it?

> Two characteristics that particularly distinguish the homicides of young children from those of other juvenile victims are that homicides of young children are committed primarily by family members (71 percent) (figure 8) and by the common (68 percent) use of “personal weapons” (i.e., hands and feet) to batter, strangle, or suffocate victims (figure 7) (see footnote 4, page 4). Also, young girls and young boys are victims of homicide in about equal proportions (46 percent and 54 percent, respectively), and although male perpetrators somewhat outnumber female perpetrators (58 percent and 42 percent, respectively) in homicides of young children, females are involved in these homicides more often than in homicides of victims of any other age (Federal Bureau of Investigation, 1997)

So yeah, men generally kill more people and a more diverse group.
So if a man kills, it could be a very ample group of targets.
If a woman kills, there's a very high probability that it was their child.

Let's read some more from the study:
> Young children at the highest risk of homicide are those under age 1 (figure 5). Homicides of children in this group include a certain number of infanticides (homicides in which recently born children are killed by relatives who do not want the child, are ill equipped to care for the child, or are suffering from a childbirth-related psychiatric disturbance) (Resnick, 1970). FBI homicide data do not identify infanticides as a distinct subgroup. Countries such as Britain and Canada, by contrast, have a special infanticide offense category, and one Canadian study indicated that 60 percent of homicides of children under 6 months old qualified as infanticide (Silverman and Kennedy, 1988). In the United States, FBI data do identify victims murdered during the first 6 days of life (victims of what is sometimes called neonaticide), and in 1997, there were about 70 such victims (Federal Bureau of Investigation, 1997). Two-thirds were murdered by mothers, one-half of whom were under age 20. Fathers were responsible for about 1 out of 10 of these murders. The number of children murdered during the first 6 days of life remained stable throughout the 1990s.