AUSTIN — A federal judge on Tuesday blocked key provisions of Texas’ new law requiring a doctor to perform a sonogram before an abortion, ruling the measure violates the free speech rights of both doctors and patients.

U.S. District Judge Sam Sparks upheld the requirement that sonograms be performed, but struck down the provisions requiring doctors to describe the images to their patients and requiring women to hear the descriptions.

The law made exceptions for women who were willing to sign statements saying they were pregnant as a result of rape or incest or that their fetus had an irreversible abnormality. Sparks questioned whether the Republican-controlled Texas Legislature was trying to “permanently brand” women who are victims of sexual assault.

The law — one of dozens of anti-abortion measures that advanced through state capitals across the United States this year — takes effect Thursday. The New York-based Center for Reproductive Rights had sued to block it.

Supporters argued the law ensures women fully understand what an abortion entails and said some women have regretted having abortions. They said the law would lead to fewer abortions in Texas. About 81,000 abortions are performed every year in Texas.

Opponents argued that requiring doctors to describe a fetus’ features would force them to say things against their will and would violate medical ethics requiring doctors to respect a patient’s autonomy and act in the patient’s best interest.

The Texas Medical Association opposed the law because it dictated when a doctor must perform a procedure and how the doctor must deal with a patient. While a pre-abortion ultrasound is routine, it is not considered medically necessary.

Sparks wrote that forcing doctors to discuss the results with a patient who may not want to listen “compels physicians to advance an ideological agenda with which they may not agree, regardless of any medical necessity and irrespective of whether the pregnant women wish to listen.”

Sparks was particularly troubled by the requirement that victims of sexual assault or incest sign statements attesting to that fact to get around the provision. That would require women to disclose “extremely personal, medically irrelevant facts” that will be “memorialized in records that are, at best, semi-private,” Sparks wrote.

“[It] is difficult to avoid the troubling conclusion the Texas Legislature either wants to permanently brand women who choose to get abortions, or views these certifications as potential evidence to be used against physicians and women,” Sparks wrote.

Sparks also struck down several enforcement penalties for doctors who faced losing their medical license and possible criminal misdemeanor prosecution if they did not comply.

The ruling is a “huge victory for women in Texas and a clear signal to the state Legislature that it went too far when it passed this law,” said Nancy Northup, president and CEO of the Center for Reproductive Rights.

The group said it had already received notice the state plans to appeal.

Texas Gov. Rick Perry, a Republican running for president, was critical of Tuesday’s ruling.