Does IVF Cause Cancer?
In Vitro Fertilization (IVF) is a revolutionary procedure that has empowered countless people worldwide to fulfill their dreams of parenthood. However, amidst the inspiring success stories, there can be a lingering concern for some: does IVF cause cancer?
It makes sense to ask this question when considering that fertility drugs can have a dramatic impact on various sex hormones. However, the available data tells us that the use of fertility drugs is not associated with a meaningful increased risk of cancer in general or with invasive ovarian cancer, breast cancer, or endometrial cancer in particular.
In this article, we’ll address these concerns by using the most recent scientific research to help us navigate the maze of misinformation and separate fact from fiction.
Where Does the Fear that IVF Causes Cancer Come From?
Worldwide, the use of IVF has increased to around 1 million in vitro fertilization (IVF) cycles each year. Additionally, there are likely millions more ovulation induction cycles for timed intercourse cycles at home and intrauterine insemination (IUI). In America alone, from 1990 to 2022, there has been a 153X increase in the use of IVF to over 300,000 cycles per year.
The fear that IVF may cause cancer is linked to the use of medications that stimulate hormones to induce ovulation and produce multiple eggs. These medications contain hormones such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Some studies have associated generally higher levels of these hormones ((but not specifically fertility medications) with an increased risk of breast and ovarian cancer.
While concerns about the potential link between IVF and cancer are theoretically understandable, the current scientific evidence does not support a causal link.
Let’s take a look at what the science has to say about the impact (or lack thereof) that IVF has on the risk for various cancers.
Breast Cancer
There have been over thirty mainstream studies and seven systematic reviews/meta-analyses (the gold standard of research) exploring the relationship between the types of fertility drugs used in IVF treatment and breast cancer.
The overwhelming majority of these studies, and all the systematic reviews/meta-analyses, have shown that there is no significant increase in the risk of breast cancer from IVF treatments.
Additionally, many of the studies found that the risk of breast cancer after infertility treatment actually decreased in comparison to both the general population and women who are infertile and have not undergone treatment with fertility medications.
A large-scale 2012 Australian study surveying all the women who had sought IVF treatment in hospitals between 1983 and 2002 (21,025 total) found that there is no overall increase in the rate of breast cancer in those who underwent IVF compared to the general population (HR 1.10, 95% CI 0.88–1.36).
Another large cohort study published in 2014 looked at the rates of breast cancer for 12,193 women who underwent fertility treatment between 1965 and 1988. The researchers found that the 38% of the women who used the fertility drug clomiphene citrate had no increased risk of breast cancer compared to women who didn’t use this drug. The study did find that the use of Gonadotropins was associated with a small increased risk of breast cancer for women who did not ultimately conceive, but had no association for women who did get pregnant.
However, another study that followed up with participants after 30 years revealed that inducing ovulation using gonadotropins did not show an elevated risk of breast cancer compared to the anticipated rates in the general population.
A 2016 meta-analysis examining the studies cited above, along with dozens of other studies, concluded that “there is fair evidence that fertility drugs [typically used in IVF treatments] are not associated with an increased risk of breast cancer.”
The study authors point out that though prolonged periods of high progesterone are associated with an increased risk of breast cancer, and certain fertility medications do elevate progesterone, it is important to remember that IVF treatments only increase hormones for short periods of time.
Ultimately, the scientific consensus is that fertility drugs are not causally linked, nor are they associated with an increased risk of breast cancer.
It’s also important to highlight that many of the studies we’ve looked at use long-term follow-ups of 10 years or more. Since we know that cancer often doesn’t show up until years after exposure to potential risk factors, these studies are particularly reassuring.
Ovarian cancer
The question of whether IVF causes ovarian cancer stems from observational links between prolonged and uninterrupted ovulation over many years and an increased risk of ovarian cancer. This is called the ‘incessant ovulation’ theory.
This theory is supported by the fact that women who have been pregnant or had their ovaries suppressed through birth control for long periods of time have a lower risk of ovarian cancer.
According to this theory, birth control pills may lower the risk of ovarian cancer by reducing the number of times that the surface of the ovary is disrupted by ovulation. Since the use of fertility drugs stimulates multiple eggs to be released from the ovaries each cycle, there has been speculation that this may increase the risk of ovarian cancer.
However, research has not shown that taking fertility drugs for a short time during fertility treatment affects the risk of ovarian cancer later in life. There’s also speculation that getting pregnant with fertility treatments may cancel out this theoretical increase in the risk of cancer. Furthermore, new evidence questions the idea that ovarian cancer always starts in the ovaries. Instead, it’s now believed that more aggressive forms of ovarian cancer begin in other organs in the pelvis, such as the fallopian tubes, and then spread to the ovaries.
According to the research assessing these links, most studies have not found a significant increase in ovarian cancer risk with the use of fertility drugs compared to infertile individuals or the general population.
For example, a large study of over 87,000 women found that the risk of ovarian cancer in women who used fertility drugs or underwent IVF was no higher than for the general population.
Another study with over 54,000 women found that over a 16-year period, there was no increased risk with specific fertility drugs like clomiphene citrate or gonadotropins.
Multiple systematic reviews of dozens of studies have not found a significant increase in ovarian cancer risk with the use of fertility drugs compared to infertile women or the general population.
The largest review by the Cochrane Collaboration included nearly 183,000 women. It found that most case-control and cohort studies showed no increased risk of ovarian cancer with fertility drug use. Only two cohort studies reported a relatively higher risk. Even so, the researchers’ overall conclusion was that there is no convincing evidence linking fertility drugs to an increased risk of ovarian cancer.
Endometrial cancer
Most research finds no significant increase in endometrial cancer risk with overall fertility drug use, including clomiphene citrate (CC) or gonadotropins.
For instance, a large study of over 12,000 infertile women followed for 26 years found no significant increase in endometrial cancer risk with CC, gonadotropins, or their combination.
Similarly, a study of more than 2,400 infertile women over 20 years found no increased risk with CC or human menopausal gonadotropin (hMG) but noted a possible increase when CC and hMG were combined.
Furthermore, many studies have found more cases of endometrial cancer in infertile women, especially those who have problems with ovulation, such as PCOS or those with infrequent or irregular periods, low progesterone levels, or are overweight.
Again, the scientific consensus is that fertility drugs are not causally linked nor associated with an increased risk of endometrial cancer.
Borderline Ovarian Tumors
Borderline ovarian tumors (also called tumors of low malignant potential) are less serious ovarian tumors, making up about 15% of all ovarian tumors. Though there is no evidence connecting fertility drugs to invasive ovarian cancer, some studies suggest a link to borderline ovarian tumors.
One study found that among women who underwent IVF, there were more cases of borderline ovarian tumors compared to those who didn’t have IVF. Out of 7,544 women who did IVF, 17 women had borderline ovarian tumors. Of the 14,095 women in the non-IVF group, there were 14 diagnosed cases.
Even so, multiple other studies did not find a higher risk of borderline ovarian tumors with fertility drug use.
The largest study looking at IVF drugs and borderline ovarian tumors followed 100,000 Danish women with fertility problems for 11 years. 142 were found to have borderline ovarian tumors. The researchers determined that using fertility drugs did not increase the risk of these tumors.
In summary, there have been a few studies showing that fertility treatments are associated with a small increase in the absolute risk of borderline ovarian tumors, but there is not enough evidence to link any particular fertility drug to these small increases. Ultimately, the evidence does not support avoiding fertility medications used in IVF to avoid borderline ovarian tumors.
Other Cancers?
There have been far fewer studies on the possible effects of IVF (based on the use of typical fertility drugs) on other cancers.
What we do know is that, in general, studies show that fertility drugs do not appear to raise the risk of invasive thyroid cancer, colon cancer, or cervical cancer.
Does IVF Cause Cancer: The Bottom Line
From the available evidence, we find that using fertility drugs does not significantly increase the chances of getting invasive ovarian, breast, or endometrial cancer.
Though some studies find a slight increase in the risk of borderline ovarian tumors, it is not clear if any specific fertility drug is to blame, and the overall risk is so small that researchers do not recommend against IVF as a way of avoiding borderline ovarian tumors.
Ultimately, the research shows that women struggling with infertility may have a slightly higher risk of ovarian, endometrial, and breast cancer. These marginal increases are linked to underlying health issues that cause infertility, not the use of fertility medications. Using IVF has not been causally linked or associated with an increase in the risk of any cancer, and in the case of breast cancer, may even decrease the risk.
Whether you’re just testing the waters or already riding the current of the complex IVF journey, this news can provide substantial emotional solace and reassurance.
