Fertility treatment was not linked to a higher overall risk of invasive cancer in women, a large Australian study has found.

The study, published today in JAMA Network Open, analysed health records of more than 417,000 women and found some specific cancers were slightly more common, while others were less common.

The researchers said the findings need to be interpreted with caution, and in the context of the many factors that influence cancer risk.

Adrian Walker, joint lead author from UNSW’s Centre for Big Data Research in Health, said the overall findings were reassuring, with women who receive fertility treatment not having a higher total incidence of cancer than other women.

“Women who’ve had assisted fertility should continue to participate in routine cancer screening programs they’re eligible for,” he said.

“And they should discuss their cancer risk with their doctor, to understand how else they can reduce their risk.”

The study analysed national health and cancer records from 417,984 Australian women who underwent medically assisted reproduction between 1991 and 2018.

This included IVF, intrauterine insemination and treatment with the fertility drug clomiphene. Cancer outcomes were examined over an average of 10 years.

The researchers compared how often cancer occurred in these women with how often it occurred in Australian women of the same age and in the same calendar years.

While the overall cancer rate was not higher, some specific cancers were slightly more common in women who had fertility treatment, while others were less common.

Uterine and ovarian cancer were slightly more common, as was melanoma. A non-invasive form of breast cancer was also more common in women who had IVF, but invasive breast cancer was not increased.

At the same time, some cancers, including cervical and lung cancer, were less common.

“It is very normal for a specific group of people to have a slightly different cancer profile from the general population,” Walker said.

“But as we see here, that doesn’t mean that their overall risk is increased.”

Claire Vajdic, professor at UNSW’s Kirby Institute and study lead, said the findings need to be interpreted carefully.

“This study focused on comparing rates of cancer in different populations, not whether fertility treatments themselves cause cancer.

“As such, we must consider the pre-existing risks of cancer in these populations when interpreting the findings.

“Women with infertility who are having or have had treatment, like all women, should ensure that they have regular check-ups, and seek further evaluation if they have concerns about unusual symptoms.”

Of the cancers that occurred at a higher rate than in the general population, uterine cancer was between 23 per cent and 83 per cent more common, depending on the type of fertility treatment.

Ovarian cancer was around 18 per cent to 23 per cent more common in women who had IVF or related treatments, while melanoma was about 7 per cent to 15 per cent more common.

On the other hand, some cancers were less common. Cervical cancer rates were about 40 per cent lower than in the general population, and lung cancer rates were about 30 per cent lower.

However, when the researchers looked at the actual number of additional cases, the difference was small. Across the cancers that were more common, the largest increase amounted to three to seven extra cases per 100,000 women per year.

So even where a relative increase was observed, the overall chance of developing cancer remained low.

Very few medical treatments are without risk, but the elevated cancer incidence here is low,” Vajdic said.

The researchers said there could be many reasons why certain cancers were more common in women who had fertility treatment.

“Women who need fertility treatment may differ from other women in ways that affect cancer risk,” Vajdic said.

Certain underlying causes of infertility, such as endometriosis and polycystic ovary syndrome, are known to increase the risk of uterine and ovarian cancers.

The researchers showed Australian women who underwent fertility treatment were more likely to live in major cities and be socioeconomically advantaged.

Although not examined in this study, women having fertility treatment are also more likely to have fair skin and be less likely to smoke. Additionally, before starting fertility treatment, doctors must check that women are up to date with any recommended routine cancer screening.

All these factors will contribute to the cancer patterns observed in this study, including reduced lung cancer rates and reduced cervical cancer rates.

“What this study does is describe cancer patterns we’re seeing at a population level,” Walker said.

“It doesn’t tell us the risk of receiving treatment, or the risk for individual women who undergo treatment.”

Because many women in the study were still relatively young at the end of follow-up, the researchers said longer follow-up would provide additional insights.

“Continued cancer awareness is important as this population ages,” Vajdic said.

The researchers concluded that cancer risk after fertility treatment was not higher overall, and that further research to better understand differences in incidence for individual cancers will help women and their doctors make informed decisions.

Maternal antibodies may protect babies from severe newborn infection caused by E. coli, after a study found the sickest infants had far lower levels.

A multi-centre study has shed new light on why some newborns become severely ill from Escherichia coli, or E. coli, while others do not.

The findings suggest most babies are protected by germ-fighting antibodies passed on by their mothers.

Sing Sing Way, an expert on immune system changes in expecting mothers and babies in the division of infectious diseases at Cincinnati Children’s and senior author on the study, said: “This helps explain a long-standing question: if most babies are exposed to germs soon after birth, why don’t even more develop severe infection?

“Our findings provide a key missing piece to this puzzle, the antibodies stimulated by the presence of these common bacteria in our intestines protect us against infection. 

“In pregnancy, the natural transfer of these germfighting antibodies from mothers to babies in the womb protect the vast majority against infection.

“In the rare situation when these antibodies are low in mothers or inefficiently transferred, babies are at much higher risk for infection.”

The study examined why only some babies develop severe infection from common bacteria.

E. coli is a common bacterium that lives in the intestines of nearly all people and is a leading cause of severe infection in newborn babies.

The research found that the babies who became most severely ill from E. coli infection also had markedly lower levels of germ-fighting antibodies transferred from their mothers.

The multi-centre research was led by Cincinnati Children’s, in collaboration with the University of Queensland in Australia, the University of Texas Southwestern Medical Center, Children’s Mercy Kansas City and the University of Missouri Kansas City School of Medicine.

To conduct the study, researchers retrieved dried blood samples collected during routine newborn screening from 100 babies who eventually developed E. coli infection and compared their antibody levels with those of hundreds of other infants who did not.

The analysis found that antibodies targeting E. coli were consistently reduced in infected babies. Because E. coli can vary widely, the researchers used a panel of strains isolated from infected babies to assess levels of these germ-fighting antibodies.

In a separate part of the study, the researchers used mice raised without any exposure to E. coli and therefore lacking the relevant antibodies.

They found that introducing a probiotic strain of E. coli, called Nissle 1917, to mice before pregnancy stimulated production of protective antibodies that efficiently protected newborn mice against infection.

The probiotic is widely available for human use in Europe, Asia and Australia under the trade name Mutaflor.

Mark Schembri, co-author and researcher at the Institute for Molecular Bioscience at the University of Queensland, said: “Understanding protection takes both types of evidence, what we can evaluate from specimens in human babies that naturally develop infection, and what we can test by experimentally causing infection.

“By strategically combining real-world human newborn screening samples with carefully designed infection models, we can start to pinpoint which antibody targets matter most and how broad protection might be achieved.”

Susana Chavez-Bueno, co-author from Children’s Mercy Hospital in Kansas City, said: “Neonatal sepsis can escalate quickly, and clinicians need better ways to identify which infants are at highest risk. These findings suggest a path toward earlier risk recognition and eventually, prevention strategies built around restoring the missing protective maternal antibodies.”

The researchers said they plan to develop a screening test to identify newborns at highest risk of severe E. coli infection, and eventually a probiotic that could be safe for mothers and strengthen their own immunity as well as the immunity transferred to their babies.