In February, Cleveland Clinic made the landmark announcement that a team of transplant and gynecological surgeons had performed the first uterus transplant on U.S. soil. For a few weeks, all was well with the 26-year-old patient, who was told at 16 that she could not bear children. Then, just days after the patient was seen in a press conference looking healthy and hopeful, the clinic announced that the transplant had failed and the uterus was removed.

Now, Cleveland Clinic has announced the culprit of the failed transplant: a yeast infection.

According to a written statement: “Preliminary results suggest that the complication was because of an infection caused by an organism that is commonly found in a woman’s reproductive system. The infection appears to have compromised the blood supply to the uterus, causing the need for its removal.”

The New York Times reports that two of the doctors said in an interview that the infection was caused by a type of yeast called Candida albicans. Because this yeast is usually found in the genital tract and because there was vaginal tissue in the transplant, it could have come from either the donor or recipient.

While yeast infections are common and easily treatable with over-the-counter medications, in a transplant patient they can be deadly. Transplant patients have to take antirejection medicine and those same drugs also stop the immune system from warding off infection.

Even worse, in the transplant patient, known as Lindsay, the infection spread to an artery that was connected to the uterus to provide blood flow – a situation that damaged the vessel and caused clots. The complication caused Lindsay to begin bleeding heavily.  

Once the issue was discovered, Lindsay was immediately rushed into surgery to remove the uterus. The doctors treated the infection, and a week later she had to have another surgery to stop further bleeding.

Previously, Cleveland Clinic said that it planned to continue its clinical trial of 10 uterus transplants. But two doctors from Cleveland Clinic said they are planning to delay further transplants until they had settled on a new protocol to prevent another infection-related complication. They team said they are considering measures such as antifungal medications and washing donor tissue to reduce infection risks.

Uterus transplants have been performed in a number of countries. But only one team in Sweden has succeeded in bringing a healthy baby into the world, which was delivered in 2014. All told, uterus transplants in Sweden have resulted in five births after a total of nine transplants.

The Cleveland Clinic is the first to attempt a uterus transplant in the U.S. But two other hospitals – Baylor University Medical Center in Dallas and Boston’s Brigham and Women’s Hospital – have been approved for uterus transplant studies.