CONCORD, N.H. – A bill that would make causing the death of a fetus a homicide passed the Senate on Thursday, but it cannot become law until differences are resolved with the House over how old the fetus should be before charges can be filed.

The Senate and House have both voted in favor of charging someone with first-degree murder, second-degree-murder or negligent homicide for causing a pregnant woman to lose her fetus. The legislation would make exceptions for medical procedures such as abortion.

The House passed a bill in January that would apply to fetal deaths after 24 weeks of pregnancy. The Senate amended the measure to set the threshold at eight weeks after rejecting attempts to set it at conception or viability, then voted to send the bill back to the House on Thursday.

The House will now have to decide whether to accept the Senate’s changes; otherwise, a conference committee would need to work out a compromise before the bill could go to Gov. John Lynch.

A spokesman for Lynch said the governor has serious concerns about the Senate’s version but would be open to a bill based on a standard of viability.

Sen. Raymond White, R-Bedford, supported applying the law to deaths any time after conception. “I didn’t want to leave anybody behind,” he said.

But Sen. Matthew Houde, D-Meriden, said that would criminalize the destruction of embryos created through in vitro fertilization. He offered the proposal to set the threshold at viability, arguing that if it was set any earlier, it would be all but impossible for prosecutors to prove a woman was pregnant without delving into her private medical records.

Opposing Houde’s proposal, Sen. Fenton Groen spoke of his daughter, who is 20 weeks pregnant.

“This is not some esoteric discussion of when murder exists or when life exists, this is a baby we’re looking forward to and that my daughter feels kicking, and this amendment would not address that,” said Groen, R-Rochester.

He also addressed opponents’ argument that it is often difficult to determine how far along a woman is in early pregnancy.

“In the case of fetal homicide, there is always a dead body,” he said. “This isn’t a matter of guesswork. This is a matter of examining the dead fetus.”

The bill was inspired by a 2006 case in which a drunken driver ran a red light and slammed into a cab driven by a woman who was seven months pregnant. The baby was delivered by cesarean section after the crash but was not breathing and had no heart rate; he was put on life support and died two weeks later.

The driver was convicted of negligent homicide, but the state Supreme Court overturned the conviction because state law does not consider a fetus a person unless the baby shows evidence of life at birth, such as breathing or moving spontaneously.