By Brendan Pierson

South Carolina's highest court on Wednesday upheld a new state law banning abortion after fetal heart activity is detected, usually around six weeks of pregnancy, months after it blocked a similar ban.

In a 4-1 ruling, the South Carolina Supreme Court found that the state constitution's protection against "unreasonable invasions of privacy" did not include a right to abortion, and that the state law was "within the zone of reasonable policy decisions rationally related to the State's interest in protecting the unborn."

"With this victory, we protect the lives of countless unborn children and reaffirm South Carolina's place as one of the most pro-life states in America," South Carolina Governor Henry McMaster, a Republican, said in a statement.

Planned Parenthood, which had sued to challenge the law, did not immediately comment.

The state legislature passed the hotly contested bill in May, mostly along party lines, with the notable exception of the state Senate's five women members - three Republicans, a Democrat and an independent - who all opposed it.

The new law came after the state Supreme Court in January struck down a previous abortion law, by a 3-2 vote.

However, the author of that ruling, Justice Kaye Hearn, has since retired. South Carolina's Republican legislature in February replaced Hearn, who was the sole woman on the five-member court, with Justice Garrison Hill, who voted to uphold the new law on Wednesday.

Justice John Few also switched his vote, finding that the new law addressed gaps in the old one by explaining the legislature's rationale more fully and by requiring health insurance plans to cover contraception.

Chief Justice Donald Beatty dissented, saying the new law was essentially the same as the previous one that the court had struck down and that the court should have followed its earlier finding.

"Today's result will surely weigh heavily upon the public and our state's medical professionals, in light of the threat of criminal penalties placed upon practitioners and the serious harm that could occur to women who could be denied reproductive health care during this uncertainty," he wrote.

(Reporting By Brendan Pierson in New York; editing by Jonathan Oatis)