A congressional hearing on Planned Parenthood’s tissue-donation program Wednesday devolved into an ideological clash over abortion rights as lawmakers sparred over the definition of “baby” and the appropriateness of certain abortion techniques.

Planned Parenthood officials were not invited to testify at the hearing before the House Judiciary Committee, nor were activists with the Center for Medical Progress, an antiabortion group whose undercover videos targeting the women’s health organization triggered the hearing.

Instead, lawmakers called four witnesses. Three were abortion foes, including two women who said they survived their mothers’ abortion attempts.

The questioning began with Rep. Bob Goodlatte (R-Va.), the committee chairman, graphically describing the dilation-and-evacuation procedure, which is often used for abortions taking place after the first trimester. It can involve dismembering the fetus and removing it from the uterus in pieces.

“Do you believe this practice represents a humane way to die?” Goodlatte challenged Priscilla Smith, a Yale University law professor and reproductive rights activist who was the sole abortion rights advocate to testify.

“I believe for a pre-viable fetus that, yes, dilation and evacuation is a very humane procedure,” Smith responded.

As the exchanges grew more heated, lawmakers all but ignored the matter that prompted the hearing: an undercover video project mounted by the Center for Medical Progress aimed at proving that Planned Parenthood clinics illegally sell aborted fetal body parts to research companies for a profit.

Planned Parenthood has denied that allegation, as well as suggestions that it uses banned abortion techniques or illegally alters the procedure to procure better tissue samples. It has described the donation program as a voluntary service offered at a handful of clinics around the country to women who find comfort in the idea of the tissue being used to further medical science.

But the videos have thrust the issue of abortion more broadly back into the spotlight, especially given the sometimes cavalier descriptions of abortion procedures captured on hidden video by the undercover activists. Cecile Richards, president of the Planned Parenthood Federation of America, has apologized for the tone of the first video, which showed an official of the organization graphically discussing abortion techniques over a lunch of salad and wine.

Wednesday’s hearing was the first of several scheduled in the coming weeks as GOP lawmakers push to strip Planned Parenthood of federal funding in spending bills set to take effect in the new fiscal year, which starts Oct. 1.

Antiabortion senators are also pushing for a vote on a measure that would ban most abortions after 20 weeks. The Pain-Capable Unborn Child Act has passed the House but is stalled in the Senate and would face a likely veto from President Obama.

Republicans on the Judiciary Committee defended the wide-ranging nature of Wednesday’s hearing, which was titled “Planned Parenthood Exposed: Examining the Horrific Abortion Practices at the Nation’s Largest Abortion Provider.”

Rep. Trent Franks (R-Ariz.) dismissed efforts by Democratic lawmakers to steer the conversation back to the tissue-donation program, asserting that the videos illustrate a larger problem with Planned Parenthood and abortion in general.

“If you look at the videos you do see that these little body parts represent what once was a living, feeling human child,” he said. “And that when they came into Planned Parenthood they were living, feeling human children. They died a brutal death while they were there.”

Smith, the Yale law professor, was repeatedly challenged over her use of the term “pre-viable fetuses” rather than “babies,” which some of the antiabortion members preferred. In her view, she said, the term “baby” gives an incorrect and biased image.

“That makes us think about full-term gestated babies rather than fetuses in a very early stage of gestation,” she said. “When you juxtapose those images in your mind, it becomes very distasteful.”

In 2007, Smith represented a Maryland abortion provider who unsuccessfully challenged the federal “partial-birth abortion” ban, in a case that went before the Supreme Court.

Perhaps the most emotional testimony came from Melissa ­Ohden and Gianna Jessen, who were born alive in 1977 during failed saline abortions, a now-rare procedure that involves injecting a chemical solution into the amniotic sac.

Born many weeks too early and each weighing less than three pounds, Ohden and Jessen were treated at the hospitals where the abortions were performed and later placed with adoptive families. Ohden said she believes she would not have been so lucky had she been born in a Planned Parenthood clinic.

“I have long believed if my birth mother’s abortion had taken place at a Planned Parenthood,” she testified, “I would not be here today.”