Washington, May 31 (IANS): Louisiana Democratic Governor John Bel Edwards has signed a bill into law that will ban abortions in the US state once a heartbeat is detectable with no exceptions for rape or incest, according to his office.

Louisiana joins Mississippi, Ohio, Georgia, Kentucky and Missouri, which have all passed so-called "heartbeat" bills this year, CNN reported.

Along with Alabama's near-total ban on abortion, the heartbeat bills are part of a conservative nationwide push to bring a Supreme Court challenge to the landmark 1973 Roe v. Wade ruling that legalised abortion in the US.

Edwards signed the bill into law on Thursday after it passed the state House by 79-23 on Wednesday.

It would "prohibit the abortion of an unborn human being with a detectable heartbeat", which can occur as early as six weeks into a pregnancy, before many women know they're pregnant.

The bill would require an ultrasound prior to an abortion and subject doctors who perform abortions after a heartbeat is detected with a $1,000 fine or up to two years in prison.

The bill was introduced by Republican state Representative Valarie Hodges, who called it "a very solemn responsibility", reports CNN.

The Louisiana law will go into effect only should a federal appeals court uphold a similar Mississippi law.

The federal judge hearing the case expressed deep scepticism toward the Mississippi measure last week, especially its lack of exceptions for rape or incest.