What is secondary infertility?
Secondary infertility is defined as the inability to get pregnant or have a healthy baby after previously getting pregnant and giving birth, even if they did so the first time without any issues. For many women, secondary infertility can come as a huge surprise. But as women age, our fertility declines, and new issues affecting fertility can crop up in us and in our partners—and those factors can make all the difference between an easy conception and infertility.
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Secondary infertility statistics tell us this experience is more common than you might think. A 2013 report by the CDC estimated that, between 2006 and 2010, over 3.6 million women of childbearing age experienced secondary infertility. That’s about 39% of all women experiencing impaired fertility during that time.
What are the causes of secondary infertility?
Like infertility in general, a very common cause of secondary infertility is age. This makes sense when you consider that the only inevitable change for everyone between their previous babies and now is time—and time = age.
Think about it this way: if a woman or couple waits a few years between babies, that’s a few years of additional fertility decline—which can mean a lot, especially for a woman in her 30s. We know that fertility enters a steeper decline in a woman’s 30s, as both the number and quality of her eggs drops. Women are born with all the eggs they’ll ever have; at 30, about 10% of those eggs remain. By 35, a woman’s egg count is just 6% of the original.
But the more impactful decline—and what’s more likely to contribute to secondary infertility—is egg quality. Egg quality refers to the genetic health of an egg, which determines its ability to fertilize and develop into a healthy baby. As a woman ages, her eggs are more likely to contain chromosomal abnormalities (mistakes in their DNA). When eggs are fertilized to create embryos, their genetic health can be tested; while over 70% of embryos created from 30-year-old eggs are genetically normal, that number drops to just 40% for embryos created from 40-year-old eggs. It’s the confluence of these two factors—that there are fewer eggs, and that a lower percentage of the remaining eggs are healthy—that results in age-related infertility or secondary infertility.
It’s not all about women, though—the age of the male partner (or sperm donor) affects the chances of secondary infertility, too. While male fertility decline is slower and is less significant than women’s, there’s evidence to suggest that men in their mid to late 40s could experience a decrease in sperm quality—or other sexual issues—that may affect their ability to impregnate their partner.
New or progressing health conditions
In addition to age, the time between pregnancies may bring new or worsening health conditions that can cause secondary infertility.
Endometriosis is an illness in which endometrial tissue—which usually lives inside the uterus—begins to grow on other organs inside a woman’s body, like the ovaries, the outside of the uterus, or Fallopian tubes. These tissues grow, thicken, breakdown, and bleed just like the endometrium inside the uterus, except because they’re outside, this cycle can cause irritation or inflammation in surrounding organs or even produce scar tissue, known as “adhesions,” that can cause organs to attach to each other.
Endometriosis is a progressive illness, meaning it will continue to worsen unless treated (and sometimes, despite treatment). So even if a woman with endometriosis has no problem getting pregnant once or even more than once, the progressive illness may have a much larger impact on their ability to get pregnant later, resulting in secondary infertility.
New problems with the female reproductive system
Between pregnancies, there are any number of illnesses or issues that could develop that may contribute to secondary infertility. One example is pelvic inflammatory disease, typically a complication of sexually transmitted infections, such as chlamydia or gonorrhea, that are left untreated. PID happens when microorganisms from one of these STIs travel upward from the cervix or vagina to the other reproductive organs, causing them to be infected, as well. The PID, in turn, can cause scar tissue on the fallopian tubes that blocks the pathway of the egg released from the ovary, preventing natural pregnancy and causing infertility.
Other examples includes ovarian cysts and uterine fibroids, both very common conditions among women in their 20s, 30s, and 40s. While cysts or fibroids don’t always cause fertility problems themselves (though they can), treatment or surgery used to remove or reduce the symptoms of these conditions can affect the ovaries and the egg supply, contributing to secondary infertility.
Finally, secondary infertility comes after one or more previous pregnancies. If those previous pregnancies came with complications, such as a Caesarean section that caused uterine adhesions or a retained placenta that caused scarring, a woman can experience secondary infertility as a result.
New problems with the male reproductive system
Fertility is a two-way street! There are many issues with the male reproductive system that can develop between pregnancies and contribute to secondary infertility, including problems with sexual intercourse or ejaculation, infections in or injury to the testicles, or varicocele, a swelling of veins in the testicle. Learn more about male fertility decline.
What can I do to treat or prevent secondary infertility?
Secondary infertility treatment varies, based on the cause of the fertility issues. Many women or couples trying to conceive with secondary infertility turn to in vitro fertilization (IVF), a fertility treatment that can help those with blocked or damaged fallopian tubes or whose fallopian tubes have been removed, those with low sperm count or decreased sperm motility, and those experiencing age-related infertility (among others).
Unfortunately, though, IVF can’t overcome all of the issues associated with age-related infertility, a common cause of secondary infertility. Statistics collected by the American Society for Reproductive Medicine (ASRM) tell us that, while over 40% of IVF cycles performed for women under 35 are successful (i.e., results in a live birth), success rates for women over 40 are less than 20%, and drop to below 5% for women over 44.
Why is this? It comes back to egg quality, which is directly tied to the age of the egg. While IVF can help women produce more eggs than they typically would, it can’t change the quality of those eggs—and the majority of eggs from a 40-year-old woman are going to be abnormal. It’s inevitable. That’s compounded by the fact that women with a lower egg count (typically older women) produce fewer eggs during IVF. Think of it this way: an average 30-year-old might produce 15 eggs during one cycle of IVF, with 80% of them being genetically healthy (or about 12 eggs). An average 40-year-old might produce 5–10 eggs, with 80% of them being genetically unhealthy—leaving only 1–2 healthy eggs to work with.
So what if you know you want a bigger family, but you’re starting a little later—or you want to wait longer between children? Egg freezing can help you avoid secondary infertility. Check out the statistics for IVF with a donor egg from a younger women, in purple in the chart above—about 50% success rate, regardless of the age of the woman getting pregnant. Egg freezing before age 35 allows a woman to be her own egg donor, improving her chances of a healthy pregnancy later on, when healthy eggs are harder to find.
This is why, when we talk to women about whether or not egg freezing is right for them—and how many eggs they should freeze—we talk not only about whether or not they definitely want to have kids, but also about how many kids they want and when they think they might start their family.