(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 the 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.
"If a ban on abortion after 15 weeks is unconstitutional, then it follows that a ban on abortion at an earlier stage of pregnancy is also unconstitutional," they wrote. "Indeed, after we held that the 15-week ban is unconstitutional, Mississippi conceded that the fetal heartbeat law must also be."
The Center for Reproductive Rights, which brought the case, said that in light of the 15-week ban, the heartbeat law "marked an even more extreme attempt to take away the rights of Mississippi residents," the group tweeted Thursday. "Not on our watch."
CNN has reached out to the Mississippi State Department of Health and to Mississippi Attorney General Lynn Fitch's office for comment.
District Judge Carlton Reeves first blocked the law in May, saying that it "threatens immediate harm to women's rights, especially considering most women do not seek abortions services until after six weeks."