A 29-year-old woman died of natural causes after visiting an abortion clinic in Montgomery County and suffering a rare complication related to childbirth, according to an initial finding by the Maryland medical examiner’s office.

The complication, which occurred when amniotic fluid was pushed into the woman’s bloodstream, can occur during or after abortions, natural deliveries or Caesarean sections.

In concluding that the woman died of “natural causes,” the medical examiner’s office chose that designation over four others used to indicate “manner of death”: undetermined, accidental, suicide or homicide.

The medical examiner listed three “causes of death.” One was “amniotic fluid embolism following a medical termination of pregnancy,” the complication involving amniotic fluid in the woman’s blood. Another was “disseminated intravascular coagulation,” a complication in which the body starts producing thousands of tiny blood clots, which have the counterintuitive effect of hampering the body’s ability to clot blood elsewhere. A third was “fetal abnormalities.”

The medical examiner’s office, which reviews about 10,000 cases a year, has yet to complete its much more detailed autopsy report, which probably will not be released for at least a month, said Bruce Goldfarb, a spokesman for the office.

He declined to comment on the case Wednesday other than releasing the cause and manner of death, which are considered public record.

The case has again cast a national spotlight on a small clinic that opened inside a nondescript office park in Germantown a little more than two years ago. The clinic’s leader, LeRoy Carhart, is one the few doctors nationwide who publicly acknowledge performing late-term abortions. He has declined to comment.

Abortion rights activists say Carhart courageously performs procedures many other doctors have quit doing. Abortion opponents say his procedures are dangerous and immoral, and they have targeted his clinic. They often demonstrate outside the clinic, as they did last week after the woman’s death.

The New York woman, whose family has declined to comment in detail about the case, first visited Carhart’s clinic on Feb. 3, a Sunday, according to abortion opponents who tried to talk to her as she entered. They said that she was 33 weeks pregnant at the time, an assertion supported by an online gift registry the woman and her husband appeared to have set up for the baby.

In the days after Feb. 3, the woman returned to the clinic several times, an indication of a multi-day abortion procedure that involved inducing labor, abortion opponents have said. Complications arose, and on Feb. 7, she arrived at Shady Grove Adventist Hospital, where state and local officials say she died that day.

Friends who have spoken with Carhart describe him as devastated by the woman’s death.

Carhart began working in Germantown after Nebraska made it illegal to perform most abortions beyond 20 weeks of gestation.

Most doctors will not perform abortions beyond 22 or 24 weeks because of moral qualms, social stigma, legal concerns, inadequate training or lack of experience. About 1.5 percent of procedures — perhaps about 18,000 a year — are done after 21 weeks. A full-term pregnancy lasts about 40 weeks.

In Maryland and Virginia, abortions are not allowed beyond a certain point in the pregnancy. In Maryland, the threshold is when the fetus becomes viable, the earliest point at which it could survive outside the womb. In Virginia, it is the second trimester.

Both states make exceptions if the woman’s “life and health” are threatened. Maryland also allows exceptions for serious genetic defects. In both states, the doctor performing the abortion makes those determinations. In Virginia, a second doctor must approve the procedure.

The District has fewer restrictions, with no specific rules for late-in-pregnancy abortions.

In reviewing the causes of death in the woman’s case, Steven H. Eisinger, an obstetrician and clinical professor at the University of Rochester’s medical school, said the complication involving amniotic fluid in the blood is often related to the clotting problems that occurred.

Eisinger, who provides expert testimony in litigation involving obstetric complications, including deaths, offered general medical explanations, but he stressed that he could not give an opinion about the case because he had no direct knowledge of the details.

Amniotic fluid embolisms are rare, and the medical profession doesn’t have a good handle on how they affect a patient’s body, Eisinger said. “It’s kind of the obstetric equivalent of getting hit by lightning,” he said. “It is usually unexpected, sudden and often fatal.”

Eisinger said he could not comment on the third cause, “fetal abnormalities,” because it represented such a broad spectrum of conditions.