The program by Naral Pro-Choice America lets people sign up to receive its text messages by keying in a message to a five-digit number. Known as "short codes," the five-digit numbers have become a popular way to get updates on everything from sports to politics to entertainment news.
Other leading wireless carriers have accepted Naral's request to use their networks.
Jeffrey Nelson, a spokesman for Basking Ridge, N.J.-based Verizon, said the topic of abortion is prohibited from mass distribution based on the company's code of content.
Nelson hinted that the policy could change, as Verizon's code of content "was initially developed at a time before text-messaging became a mass-market phenomenon."
"We have been reviewing that code for the last couple of months as text messaging and other multimedia services have become much more mainstream in American communications," he said.
Naral did not immediately return a telephone message seeking comment Wednesday night.
Nancy Keenan, Naral's president, told The New York Times, which first reported the story on its website Wednesday night, that Verizon's decision interfered with political speech and activism.
"No company should be allowed to censor the message we want to send to people who have asked us to send it to them," Keenan said. "Regardless of people's political views, Verizon customers should decide what action to take on their phones. Why does Verizon get to make that choice for them?"
Copyright 2007 The Associated Press