(Reuters) - An Indiana doctor who is suing the state over its abortion ban on Wednesday told a state judge that the exception for medical emergencies was unclear, and could prevent medically necessary abortions.

The testimony from Dr. Amy Caldwell kicked off a nonjury trial, which is expected to last through Friday. Caldwell brought case along with Planned Parenthood.

They are asking Monroe County Circuit Court Judge Kelsey Blake Hanlo in Bloomington for an order that the medical exception allows abortion if a patient has a health condition requiring treatment that would endanger the fetus, causes debilitating symptoms during pregnancy, or is likely to become life-threatening or cause lasting damage to her health.

Caldwell testified on Wednesday that the language in the law, allowing abortion in the case of a "serious health risk," was not clear enough for doctors to know when it applied. She said she had treated patients for whom she believed an abortion was indicated, but could not perform them because of the law.

"If there's any doubt about whether it's not covered (by the exception), then we don't do it," she said.

The case is one of several nationwide over the scope of medical emergency exceptions to state abortion bans. Others are pending in Texas and before the U.S. Supreme Court, which is weighing whether Idaho's abortion ban conflicts with a federal law on emergency room care.

On cross-examination, a lawyer for the state asked Caldwell whether some medical problems associated with pregnancy, such as heart issues, could be treated in ways other than abortion. Caldwell said that while that was true "to some extent," abortion was the best and safest treatment in some cases.

Stephen Ralston, director of maternal fetal medicine at George Washington University, later testified as an expert for the plaintiffs, saying an unclear exception could lead doctors to wait for a patient at risk to get sicker before ending a pregnancy.

"That's just not in anybody's best interest, to wait until patients become sick to perform care," he said.

The state will also have a chance to call witnesses in the case.

The providers are also asking the court to block a provision in the state ban requiring all abortions to take place at hospitals, saying that makes it difficult or impossible for many Indiana residents to get abortions necessary to protect their lives or health, since few hospitals provide such care and most are clustered near Indianapolis, the state's largest city.

Indiana's Republican-controlled legislature passed its abortion ban in August 2022. In addition to the life and health exceptions, the law also allows abortion in cases of rape or incest for minors in the first 10 weeks of pregnancy.

It was the first new abortion ban passed in the wake of the U.S. Supreme Court's 2022 ruling reversing its landmark Roe v. Wade precedent, which had guaranteed abortion rights nationwide. More than 20 Republican-led states now ban or significantly restrict abortion.

Planned Parenthood and others quickly sued to challenge the law. Judge Kelsey Hanlon, who was elected as a Republican, blocked it in September 2022, saying it ran afoul of the right to personal autonomy in the state constitution.

The state Supreme Court last June disagreed and revived the law, but also found that the state constitution included a right to abortion to save the mother's life or protect against serious health risks. The plaintiffs in the current trial say that supports their request for a court order clarifying that right.

(Reporting By Brendan Pierson in New York; Editing by Alexia Garamfalvi and David Gregorio)

By Brendan Pierson