AUSTIN, Texas — The Texas Legislature passed a bill Thursday that would require doctors to perform a sonogram before conducting an abortion.

Gov. Rick Perry had declared the bill to be emergency legislation, and it now awaits his signature. The proposed law requires doctors to conduct a sonogram at least 24 hours before an abortion and to provide the woman with the opportunity to see the results and hear the fetal heartbeat. The doctor is also required to describe what the sonogram shows, to include the existence of legs, arms and internal organs.

Proponents said the law is necessary to make sure women understand what an abortion entails. Opponents say the measure would interfere in the doctor-patient relationship.

"This will be one of the strongest pieces of sonogram legislation in the nation," said state Rep. Sid Miller, R-Stephenville, the bill's author. "House Bill 15 will protect human life, the lives of the unborn victims of abortion, as well as those facing life-changing decisions. ... This legislation will save numerous unborn lives."

Only three other states require a sonogram for all women seeking an abortion.

The Texas Medical Association opposed the bill because it dictates when a doctor must perform a procedure, and how the doctor must deal with his or her patient. While a pre-abortion sonogram is routine, it is not considered a medical necessity.

An exception to the waiting period was made for medical emergencies, or for women who live more than 100 miles from the nearest abortion provider. In cases of incest, rape or fetal abnormality, the woman does not have to hear a description of the fetus.

The bill passed both the House and the Senate with a two-thirds majority, meaning the law will go into effect immediately after the governor signs it. The vote on Thursday to concur with changes made in the Senate was 96-48, with three Democrats voting for the bill, and four Republicans voting against.

State Sen. Dan Patrick, who sponsored the Senate bill, said he expected the bill to reduce the number of abortions in Texas.

"We believe that if one out of five women after seeing the sonogram, hearing the explanation or hearing the heartbeat, change their mind, that's 15,000 lives that can be saved," said Patrick, a Houston Republican.

In the final debate on the bill Monday, Sen. Wendy Davis, D-Fort Worth, said the bill was clearly designed to interfere with women exercising their legal rights.

"The purpose of the bill is to traumatize women who are seeking an abortion," she said.