The Governor of Mississippi has signed a bill prohibiting abortion after a fetal heartbeat that is about six months pregnant.
The law, which will become one of the most restrictive in the US, is expected to be challenged in court before its entry into force in July.
Critics say the prohibition's purpose is "to ban the process before most women even know they are pregnant."
There are a number of new restrictions on abortion among conservative states.
"We believe this demonstrates the deepest respect and desire of the Mississippians to protect the sanctity of this unborn life whenever possible," said Governor Phil Bryant after signing Senate Bill 21
He added that he and other Republican politicians are persecuted every year "by hundreds of thousands of babies who are being murdered throughout the nation".
In Mississippi, an abortion ban was imposed after 15 weeks In November 2018, however, he was almost immediately blocked by a judge who later abrogated the law, saying it "clearly" violated the woman's constitutional right to abortion.
- US judge blocks Mississippi abortion ban