I'm perfectly prepared for the reason for this statistic...
...to be entirely the fault of the affected mothers. IF ACTUALLY LOOKING INTO THE MATTER SUPPORTS THAT EXPLANATION. Jumping to the conclusion that that is the case without research, tells more about the jumper's world view, than it does about the affected parties.
I can think of three or four alternate possibilities to your bad mother hypothesis, and I bet you could too. I hope it gets the attention it deserves from the folks administering these programs. The results of bad or no prenatal care can be tragic.