(CNN) Mississippi's law banning abortions at the detection of a fetal heartbeat -- as early as six weeks into pregnancy -- will remain blocked, a panel of circuit judges ruled on Thursday.

The decision makes the Mississippi law the first of t he abortion bans passed in 2019 to be blocked at the appeals court level.

The three-judge panel on the 5th US Circuit Court of Appeals affirmed a lower court's ruling that the Mississippi law unconstitutionally prohibited pre-viability abortions. Roe v. Wade, the landmark 1973 Supreme Court ruling, legalized abortion nationwide prior to viability, which can occur at about 24 weeks of pregnancy.

"The clinic contends it occurs at six weeks. Mississippi argues it can occur anywhere between six and twelve weeks," the judges wrote. "But all agree that cardiac activity can be detected well before the fetus is viable. That dooms the law."

The judges referenced in their decision how another panel on the 5th Circuit had similarly blocked Mississippi's 15-week abortion ban from 2018 in December.

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