Scott Walker signs 20-week abortion ban into law in Wisconsin
Governor Scott Walker of Wisconsin speaking at the 2015 Conservative Political Action Conference (Gage Skidmore/Flickr)

Wisconsin Governor Scott Walker, a Republican presidential hopeful, signed a bill into law on Monday banning abortion after 20 weeks of pregnancy that makes no exceptions for pregnancies resulting from rape or incest.

The law, which makes an exception for medical emergencies, set the cut-off at a time when some abortion rights opponents believe an unborn child can feel pain.

The American College of Obstetricians and Gynecologists disputes the threshold, saying research has found fetuses do not feel pain until 29 weeks after fertilization at the earliest.

Walker, who formally announced his bid for president a week ago, signed the bill in Oshkosh, Wisconsin, after a week-long campaign trip to early election battlegrounds such as Iowa, where he leads in the polls.

Abortion, meanwhile, became a lightning rod issue in the 2016 presidential election last week, more than a year before voters head to the polls, after a conservative group released a secret recording of a Planned Parenthood staff member discussing fetal tissue.

The law, passed the Republican-led Assembly in July and Republican controlled Senate in June, levies fines of up to $10,000 and prison sentences up to 3-1/2 years to doctors who violate it.

Wisconsin joins a dozen other states with similar bans on abortion, according to the Guttmacher Institute, a research organization tracking the issue. In May, the 9th Circuit U.S. Court of Appeals ruled Idaho's ban on abortions after 20 weeks was unconstitutional.