DENVER — The nation’s only pending ballot measure to ban abortion in all circumstances has failed to advance to voters in Colorado.

Colorado Secretary of State Scott Gessler said Wednesday that backers of the ‘‘personhood’’ amendment fell about 3,900 valid signatures short of the some 86,000 needed.

The rejection was a major setback for abortion foes in the home state of Personhood USA, which said the Colorado proposal was the only measure pending for ballots this fall. Other initiatives are aimed for future years but not this fall, Personhood USA spokeswoman Jennifer Mason said.

Personhood proposals go farther than other proposed abortion bans because they would give fertilized embryos all the rights of a born human. They also would ban embryonic stem-cell research and some fertility treatments.

The measures haven’t been backed by other abortion opponents or the Catholic church.

Personhood proposals were overwhelmingly rejected by Colorado voters in 2010 and 2008. Similar measures have been rejected by voters in Mississippi and by several state legislatures.

Colorado has a relatively low threshold for petitioning measures onto ballots, making it a hotbed for proposed citizen initiatives. The rejection of the personhood measure leaves only one citizen initiative on ballots: a proposal to legalize marijuana without a doctor’s recommendation for adults over 21.

Personhood USA vowed to fight the Colorado rejection in court. The group argues some of the signatures were improperly rejected.

Planned Parenthood of the Rocky Mountains, which campaigned against the two earlier personhood proposals and was raising money to do it again this year, lauded the rejection. Spokeswoman Monica McCafferty said support for the idea is eroding.

‘‘This year they’re not even getting people to sign on to the concept,’’ she said. ‘‘Hopefully that signals that Coloradans understand the concept, that they don’t like the outcome of what this would mean.’’