Um, first things first, lets not group ALL moms into the baby-killing category. The amount of loving, caring, amazing moms FAAARRRR outnumbers the psychos who kill their children. Second, like I said, women who do this are psychologically ill, and are not normal people. Many of these women are incredibly and obsessively religious, and I've heard many stories of women killing their children to save them from demons, or because they believe their child is a demon, or they kill their baby girls because in their religion, baby girls are bad news. Again, these women are crazy.
Lastly, killing children isn't a new trend of today. This isn't a "women of today" thing. The amount of women who purposefully murder their children is incredibly low, and is drastically lower than the amount of women who killed their children in the 1800s.