Logan Andreotta had been told she was an ideal candidate for in vitro fertilization. Though unable to get pregnant, the Bowling Green, Ky., woman was just 24 and in terrific health. But three days after she began taking fertility drugs, her ovaries went haywire and swelled with 50 eggs — four years’ worth in a single go.

“I felt like my insides were going to bust out of my stomach,” Andreotta recalled.

This was ovarian hyperstimulation syndrome — OHSS for short — a potentially fatal complication the U.S. fertility industry describes as extremely rare. But the incidence of OHSS and the broader long-term safety of hormone-boosting fertility drugs remain open to debate, even as the clinics have blossomed into a multibillion-dollar industry serving hundreds of thousands of women a year.

Industry critics worry that unregulated providers are over-prescribing the drugs, glossing over potential hazards and failing to properly report problems when they arise. One recently published study, for example, blamed “increasingly aggressive treatment protocols” for incidents of OHSS, while another argued that most cases are completely “avoidable.”

Some researchers have theorized that in addition to their link to OHSS, the drugs could have a potential link to heart disease, depression, endocrine system disorders, cancer and a host of other conditions. The few published studies are conflicting or inconclusive, however. And unlike many developed countries with government-provided health care, the United States makes no effort to track health outcomes in fertility treatments.

“Every fertility doctor says to every fertility patient, ‘There are no known risks.’ Well, there are no known risks because no one has looked,” said Diane Tober, a medical anthropologist at the University of California at San Francisco, who studies reproductive technology.

Industry advocates note that more than 8 million children have been born worldwide through IVF and other fertility treatments since the first “test-tube baby” arrived 40 years ago. Alan Penzias, an associate professor at Harvard’s medical school who chairs the practice committee of the American Society for Reproductive Medicine (ASRM), said he has been “reasonably reassured” the drugs pose no long-term threat to women’s health.

“We’re at a time point when, if there were anything major, we would have seen it by now,” said Penzias, who also serves as surgical director at Boston IVF. “Fortunately, we haven’t seen anything negative.”

OHSS is an exception. As the most brutal and immediate complication of fertility treatment, it can strike anyone taking medication to induce the ovaries to ripen multiple eggs — a fundamental step in egg freezing, in vitro fertilization (IVF) and egg donation that occurs about 240,000 times a year.

Strategies for identifying high-risk patients and treating the condition have advanced in recent years. ASRM, which represents most U.S. clinics, calls OHSS “an uncommon but serious complication” that is estimated to occur in moderate or severe form in just 1 percent to 5 percent of cycles. Fertility doctors frequently cite research showing that severe OHSS occurs in 0.03 percent of cycles.

Penzias said hospitalization for OHSS “is almost unheard of now” compared with 20 years ago. Still, a Washington Post analysis of national emergency room data found that the numbers remain significant. More than 9,000 women sought help for OHSS at hospitals between 2006 and 2014, the most recent year for which statistics are available — about 1,000 women a year.

In Sweden, Canada and Britain — countries where governments regulate assisted reproduction and track patient outcomes — medical societies tell patients that an estimated one-third of procedures trigger at least mild OHSS symptoms.

This year, Britain’s independent fertility regulator, the Human Fertilization and Embryology Authority, launched an investigation into a discrepancy between OHSS cases reported by fertility clinics and the larger number logged in hospital admissions data. While the watchdog group did not find evidence of systematic under reporting, it announced clinic-by-clinic audits, saying the data raise “significant concerns and questions about the safety of patients undergoing IVF.”

‘Wonder drugs’

When fertility-stimulating medications hit the market in the late 1960s, they were hailed as “wonder drugs” and were initially used to induce ovulation in women who were unable to produce eggs on their own. By the time the first commercial fertility clinic opened in 1979 in Norfolk, Va., doctors realized that the drugs could be used far more aggressively.

Ordinarily, a single egg ripens in a woman’s ovaries each month and is released into her uterus. Few of those eggs are destined to become babies; the rest are abnormal or defective in some way.

Collecting one egg at a time would be maddeningly inefficient for IVF. So the drugs are calibrated to trigger a batch of eggs to ripen — ideally, about 10 to 15, according to recent studies. Any fewer and a woman’s chances of having a baby go down. Any more and a woman’s own health might be endangered.

Figuring out which and how much medication to use is tricky, however. Given that IVF can cost $15,000 to $30,000 per attempt, doctors and patients often feel pressure to produce a large number of eggs in every round.

Fertility groups have developed standard dosing regimens, but each protocol must be customized to fit an individual woman’s size and health. Meanwhile, there is nothing to stop doctors who want to use bigger doses, and there is no systematic way to track dosages or outcomes.

Specialists have long argued that the short burst of estrogen, usually 10 days in IVF, is unlikely to have a profound long-term effect on a woman’s body. Researchers have argued for more research, noting that estrogen is known to promote some cancers.

The largely academic debate erupted into public alarm in 2003, when Jessica Grace Wing, a Stanford University graduate and three-time egg donor, died of metastatic colon cancer at age 32. Wing’s mother, Jennifer Schneider, a physician who focuses on internal medicine, began pressing Congress and states to pass laws requiring better tracking of fertility patients and more funding for research into complications.

“As a scientist, I cannot say that I’m 100 percent sure it was the fertility drugs” that caused the cancer, Schneider said in an interview. “All I can say is the absolute lack of any other reason for her to get colon cancer so young.”

Schneider also published pieces in medical journals that attracted the attention of researchers abroad. Large studies soon followed, involving 50,000 women who took fertility drugs in Denmark and 24,000 in Sweden. The research showed no connection between the drugs and ovarian cancer.

The latest data, presented in June at a conference in Europe, also showed no increased risk of ovarian cancer. And a study published in July found no increased risk of two other types of cancer — invasive uterine and breast — among 250,000 British women who underwent fertility treatment.

Current ASRM guidelines say “there does not appear to be a meaningful increased risk” of invasive ovarian, breast or endometrial cancer for fertility patients “based on available data.” For borderline ovarian tumors, the group acknowledges that “several studies have shown a small increased risk.”

The Post’s Dan Keating contributed to this report.