One of the few worthwhile provisions I am aware of in Obamacare is free birth control incentives for welfare mothers. I have no problem with women getting onto more effective methods like IUD and implants that they wouldn’t be able to afford otherwise. Almost all plans currently, even Medicaid, cover prescription contraceptives. Premiums will creep up - but family planning, like all preventative care/medicine, does nothing but save money in the long run. If they don’t take it up front and the behavior continues, a cut in benefits should do the trick.
One thing that might be an incentive is for the government to quit paying more money to them for each new child they bring into the world.