HOUSTON — Dr. Amanda Horton, an obstetrician who specializes in high-risk pregnancies, had been counseling pregnant patients at a small hospital in rural Texas last month when a woman arrived in crisis: It was only 17 weeks into her pregnancy and her water had broken.

The fetus would not be viable outside the womb, and without the protection of the amniotic sac, the woman was vulnerable to an infection that could threaten her life. In Colorado or Illinois, states where Dr. Horton also practices and where abortion is generally legal, there would have been an option to end her pregnancy.

Texas has a ban on most abortions, providing an exception when a woman’s life is threatened. But the patient’s life in this case was not in immediate danger — yet. The hospital sent her home to wait for signs of infection or labor, Dr. Horton said.

Worried and with nowhere else to turn, the woman instead traveled hundreds of miles to New Mexico for an abortion.

“She ended up taking matters into her own hands,” Dr. Horton said. Her patient, she said, made a choice “for her life.”

Each of the 13 states with bans on abortions allows for some exemption to save the life of the mother or to address a serious risk of “substantial and irreversible impairment of a major bodily function.”

But making that determination has become fraught with uncertainty and legal risk, doctors in several states said, with many adding that they have already been forced to significantly alter the care they provide to women whose pregnancy complications put them at high risk of harm.

Last week, the Texas attorney general, Ken Paxton, sued the Biden administration over federal guidelines that required doctors to perform an abortion, even in states with abortion bans, if they determined it was necessary to treat dangerous pregnancy complications.

Amid the legal wrangling, hospitals have struggled with where and how to draw the line. Some have enlisted special panels of doctors and lawyers to decide when a pregnancy can be prematurely ended. Others have required multiple doctors to sign off on any such decision and document in detail why an abortion was necessary.

The result has delayed treatment and heightened risk, doctors said.

“It’s like you bring lots of people to the top of a high rise and push them to the edge and then catch them before they fall,” said Dr. Alireza A. Shamshirsaz, an obstetrician and fetal surgeon who practiced in Houston until last month. “It’s a very dangerous way of practicing. All of us know some of them will die.”

The impact in these cases is on women who want to have children, only to encounter complications during pregnancy. The option to terminate the pregnancy has long been part of the standard care offered by doctors in situations where there is a risk of harm — or even death — to the mother.

The effect has been most visible in Texas, which passed a law prohibiting most abortions after six weeks of pregnancy last September — well ahead of the bans that began taking effect after the Supreme Court’s decision to overturn Roe v. Wade on June 24.

A new study of two hospitals in Dallas County found that after the Texas law went into effect, pregnant women facing serious complications before fetal viability — mostly because their water broke prematurely — suffered because they were not allowed to end their pregnancies.

Out of 28 women who met the criteria for the study, more than half experienced “significant” medical problems, including infections and hemorrhaging, in the face of state-mandated limits on treatment, the study found. One woman required a hysterectomy. And the rate of maternal health problems was far higher than the rate in other states where patients were offered the option to end their pregnancies, according to the study, which has been accepted for publication in the American Journal of Obstetrics and Gynecology.

“You nearly doubled the complication rate for the mother,” said Dr. Judy Levison, a Houston obstetrician, referring to the study, which she was not involved in. She added that all but one of the pregnancies ended with the death of the fetus. “So why did they put them through that?” she said of the women.

Last week, the Texas Medical Association sent a letter to state regulators asking them to step in after the association received complaints from doctors that hospitals were preventing them from providing abortions when medically necessary to women because of fear of running afoul of the law, The Dallas Morning News reported.

In Missouri, an abortion ban went into effect in June with an exception for medical emergencies that required immediate abortions to avoid death or injury. The word “immediate” is being pored over by hospital administrations across the state, with questions about whether it refers to an imminent danger of death or an urgent threat to a woman’s health.

Some hospitals, as in Texas, have considered internal review panels to approve medically necessary abortions to reduce their legal liability. Others are requiring that multiple doctors sign off.

“The law does not require two physicians,” said Dr. David Eisenberg, who specializes in complex family planning at Washington University in St. Louis. “But many institutions have felt like it is best to have more than one physician document the nature of the medical emergency and the need for abortion care.”

Care can differ from town to town, and hospital to hospital, doctors said.

The uncertain legal landscape has made even statewide medical associations wary of providing direction on what treatments the “life of the mother” exceptions provide.

“It is nontraditional for us to be sitting on the sidelines,” said Dave Dillon, a spokesman for the Missouri Hospital Association. Ultimately, he said, the meaning of the exception “will be decided probably by litigation.”

Until then, he said, hospitals would need to make decisions based on “whatever their pain threshold is on this individually.” For physicians, that means making decisions knowing that lawsuits or prosecutions might come later. In Texas, doctors accused of violating abortion laws face fines and unlimited civil lawsuits; when the trigger law goes into effect in the coming weeks, it could result in felony charges.

“All the physicians are complaining, but no one wants to speak up because of the possible consequences; we can be fired,” said Dr. Shamshirsaz, the Houston surgeon.

He described a colleague who had a patient with twins. At 15 weeks, she delivered one stillborn and asked to abort the other because of the risk of infection. Her case went before the hospital’s committee — what Dr. Shamshirsaz called a “termination board” — but the abortion was denied because the fetus still had a heartbeat.

“We sent the patient home against her will,” he said.

The woman returned to the hospital about two weeks later feeling sick. Her pregnancy was terminated out of concern for her health, Dr. Shamshirsaz said, but she had to be admitted to the intensive care unit for sepsis and acute kidney injury — both life-threatening conditions.

“We have to wait until the mom comes with those symptoms,” he said.

All pregnancies come with risks to the health and life of the mother. Researchers have found the risk of complications and death are higher for pregnancy than for abortion. Determining whether a woman’s life is at risk at any given point has always been a gray area, shifting as medicine advanced and as social mores changed around the acceptance of abortion.

While abortion was once mostly legal, by 1900 every state had banned abortions throughout all stages of pregnancy, with the only exception being if the life of the mother was in danger, said Jennifer Holland, a University of Oklahoma historian. Some of those laws, such as a 1925 law in Texas, have recently been revived by the overturning of Roe.

The reality during that period was that decisions about abortions were left to a family’s doctor.

There was a degree of “flexibility” over what constituted a threat to the mother, Dr. Holland said, “especially if you had access to a sympathetic family physician.”

After Roe was decided in 1973, states began passing legislation that banned abortions after fetal viability but made exceptions for “life and health,” said Elizabeth Nash, state policy analyst at the Guttmacher Institute, which supports abortion rights. Over the last decade, as state legislatures steadily passed hundreds of abortion restrictions, that language has narrowed substantially, but it has rarely been challenged in the courts.

Now with the new abortion restrictions, women — and their doctors — have found themselves traversing uncertain legal territory.

A critical care nurse in Texas, who requested anonymity to discuss her experience, became pregnant just after the restrictive abortion law went into effect last year. It was a happy occasion, but then her water broke at 19 weeks. She went to the hospital emergency room, terrified. She already knew her baby was probably going to die. But as a nurse, she also knew that her own condition was precarious. She wanted to abort the fetus but was told that all she could do was wait.

“I fought with the doctors for a while, but none of them would help me until I was actively sick,” she said. “I was just dumbfounded. I was so confused. Especially as a nurse, no one comes into an E.R. and we wait to see how sick they can get.”

She and her husband flew to Colorado for an abortion. The day of the procedure, she had a fever of 101 degrees. “I was starting to get sick that day,” she said.

Miscarriages occur in 15 percent of all pregnancies and may require a procedure — also used in some abortions — to remove the fetus. Pre-eclampsia, or pregnancy-induced high blood pressure, occurs in 5 to 8 percent of all pregnancies and can be deadly. There is a 2 percent chance a pregnancy can be ectopic, meaning the fertilized egg has implanted outside of the uterus, making the pregnancy nonviable and seriously threatening the life of the mother.

But in the new legal landscape, no one is certain how serious those conditions must get before they justify an abortion under the law.

“It’s all odds,” said Dr. Charles Brown, the Texas district chair of the American College of Obstetricians and Gynecologists. “How high a percentage does it need to take before you get everyone to agree this woman’s life is in danger?”

After Oklahoma’s abortion ban went into effect in May, Dr. Christina Bourne got a call from a patient who had an ectopic pregnancy that her obstetrician had refused to treat.

Dr. Bourne is the medical director at two abortion clinics, one in Oklahoma City and one just over the state border in Wichita, Kan., where abortion is still legal. After consultation with the clinics’ lawyers, she said, they had the woman come in to their Wichita clinic. By that time, she was already experiencing abdominal pain and bleeding and had to be transferred to a hospital for treatment; doctors there terminated the pregnancy.

“The people that we are seeing are much sicker than they were before,” Dr. Bourne said. “We are seeing the effects of a failed system. Pregnancy is where all the failed systems come to coalesce.”