SALT LAKE CITY — A Utah senator has dropped his push for a state constitutional amendment that would define life as beginning at conception, saying he wants to focus more on his public school reform bills.

Republican Sen. Aaron Osmond of South Jordan announced he was abandoning the effort in a Wednesday Twitter post.

"After carefully considering feedback from across the state and after discussing the issue with my own constituents in District 10, I have decided that I will not pursue legislation to define when an unborn child legally becomes a person at this time," Osmond also said in a blog post.

The proposed amendment would have defined "personhood," which is when a fetus is considered a human being. Similar ballot efforts are under way in at least 12 states, as proponents aim to ban virtually all abortions by defining life as beginning with fertilization.

So far, the larger personhood movement is zero for 3, losing referendums in Colorado in 2008 and 2010 and in Mississippi last November. But the movement is trying again in Colorado and expanding to all other regions except the Northeast, with proponents saying they can influence public opinion even if the measures fail.

"These are defeats only if we quit," Keith Mason, president of Personhood USA, told The Associated Press in a recent interview. "If we continue on, they are building blocks for success."

Abortion-rights activists say fighting the personhood measures is a major drain on their resources and diverts funding from their birth control or sex education efforts.

Criticism of the personhood movement also has come from some anti-abortion groups who prefer incremental legislative restrictions, such as requiring women to undergo sonograms before an abortion, or restricting insurance coverage of the procedure. Some of the organizations worry the personhood strategy could backfire if federal courts become involved and uphold Roe v. Wade.

In Utah, Marina Lowe of the American Civil Liberties Union said she's relieved Osmond took the bill off the table.