Republicans in the Iowa Senate have passed a bill that could send a person to prison for life if they cause death of a fetus, even if it's an accident and in cases where someone didn't know the mother was pregnant.

Sen. Jake Chapman amended the bill Tuesday on the floor of the Senate to make causing the death of a fetus a life-in-prison crime, the same as someone convicted of murder. Language equates such deaths to "killing an unborn person."

Chapman, a staunch anti-abortion lawmaker, denied the bill has anything to do with abortion. He argued the bill recognizes the fetus "is a person in the womb and it should have rights."

Sen. Janet Petersen says the amendment makes the bill a personhood bill and is unconstitutional.

She says it could prompt criminal investigations of women who lose babies through miscarriage or stillbirth.

The bill passed on a vote of 31-18 and goes to the House.