Secondary Infertility: What It Is and Its Causes

If you have been pregnant or given birth before, you might assume your experience trying to conceive a subsequent time will be similar to the first. For some women, this is the case. However, many couples experience difficulty becoming pregnant when they are ready to try again. This is called secondary infertility.

Secondary infertility can be a confusing and frustrating experience, especially if you expect pregnancy to happen naturally or easily. You may have envisioned a specific age gap between your last baby and your future baby. Or perhaps you planned a hopeful pregnancy around certain life events that have now long passed. Maybe you are getting questions about growing your family, adding pressure to an already stressful situation. Or perhaps just the opposite: you are receiving a lack of empathy from family and friends telling you that you should just be thankful for the child or children you already have. Many do not realize that you can be grateful for your children and still have the longing for another baby.

No matter the scenario, there is a lot of emotion surrounding secondary infertility for those going through it. There is also much to know about secondary infertility: its definition, frequency, causes, and treatments. This knowledge can give you the confidence to reach out to your doctor about what you may be experiencing and seek help.

What is secondary infertility?

Infertility refers to the inability to conceive or carry a pregnancy to term. Most providers diagnose infertility after one year of unprotected, frequent, and random acts of intercourse.^1,3,28 However, some professional reproductive organizations will not diagnose infertility until it has been two years of trying.^2,28 Other providers may diagnose infertility after only six months, especially if the woman is over 35 years old or she has a known physical complication or medical history.¹⁴

Secondary infertility is specific to the inability to conceive or carry a pregnancy to term after already having given birth at least once. This differs from primary infertility because those with primary infertility have never been pregnant or carried a pregnancy to term. The number of children a woman or couple already has is irrelevant to the diagnosis of secondary infertility.^{5, 28} For instance, you could even have three or more children and struggle to conceive again, which would be considered secondary infertility.

How common is secondary infertility?

Approximately 8-12% of reproductive-aged couples worldwide experience infertility, and secondary infertility is the most common form of female infertility.³ Secondary infertility accounts for about half of all infertility cases, and it is the most common form of female infertility worldwide.³

While it may feel like your peers are popping out second, third, and more babies left and right, it is important and reassuring to note that you are not alone. After all, one study showed over 10% of women with one baby have trouble getting pregnant again, and the CDC reports that 11% of American couples who have already had at least one child go on to experience secondary infertility.^6,26 The good news is that if you have already had a child, you are more likely to have a successful second pregnancy.⁹

Although a high rate of infertility is not the best news for society, it does mean that a lot of research is being done on the topic. Research has been able to identify causes and create interventions that prevent and treat infertility and secondary infertility.

Causes of Secondary Infertility

The causes of secondary infertility are often the same as the causes of primary infertility. They can present even after the birth of any child. Secondary infertility can be caused by the male partner, the female partner, or both.¹² Below are some of the causes of male and female factor infertility.

Female Factor Infertility

One of the leading causes of female infertility is a failure to ovulate (anovulation). This contributes to nearly one-third of all infertility cases.¹² Symptoms of ovulatory dysfunction include amenorrhea (lack of a menstrual period) or oligomenorrhea (fewer than six to eight menstrual periods in a year).¹⁵ There are also physical or anatomical causes of female infertility that can usually be diagnosed and treated via imaging and sometimes surgery.² Some of the specific female infertility causes are explained here.

1. Hypothalamic Amenorrhea

Hypothalamic anovulation or amenorrhea can be caused by restrictive diets, eating disorders, low body weight, and intense and frequent exercise. If you burn more calories than you consume daily, amenorrhea can develop. Recent weight loss is often seen in women with hypothalamic amenorrhea. Often, this condition can be reversed by increasing calorie intake and decreasing the frequency and intensity of exercise. Intense emotional stress can also cause hypothalamic amenorrhea.¹⁵

2. Obesity

Although the relationship between obesity and infertility is still being investigated, high body mass index is associated with menstrual dysfunction and anovulation. Weight loss in overweight and obese women trying to conceive has demonstrated improved reproductive outcomes.¹⁶

3. Hypothyroidism

Low levels of certain thyroid hormones can interfere with your ovaries’ ability to release an egg. Hypothyroidism can also cause hyperprolactinemia, sex hormone imbalance, and luteal phase defects. There are medications that can often easily treat hypothyroidism.¹⁷

4. Hyperprolactinemia

Prolactin is a hormone released from the pituitary gland that aids in breastfeeding. During pregnancy, prolactin prepares the breasts for breastfeeding. After giving birth, prolactin stimulates milk production. Prolactin levels can remain elevated as long as a woman breastfeeds, sometimes over a year or more. One effect of prolactin is that it suppresses ovulation, which is why many women do not get their periods while breastfeeding. This is called “lactational amenorrhea” and is normal.¹³ Some people call prolactin “natural birth control.” ¹¹ Prolactin’s suppression of ovulation can contribute to secondary infertility if you have been trying to conceive with no luck while still breastfeeding. This can usually be treated.¹³

If you are not breastfeeding but have high prolactin, this can signal a problem such as a pituitary tumor. You can be suspicious of this if you are experiencing milk leakage from your nipples while you are not breastfeeding, low libido, and painful intercourse, in addition to infertility.¹³

5. Polycystic Ovary Syndrome (PCOS)

In PCOS, high levels of circulating testosterone and estrogen can inhibit ovulation.¹⁰ If you are not ovulating, there will not be an egg to fertilize. You may think that you do not have PCOS because you have already had a child. However, PCOS can be diagnosed at any age after puberty, including after pregnancy. You can request a workup from your provider for PCOS if you are experiencing symptoms such as long cycles, irregular or very light periods, excessive body hair, weight gain, acne, or cysts on your ovaries. There are treatments available for PCOS that will help your body ovulate and help you conceive.¹⁸

6. Age

A woman is born with all the eggs she will ever have, and egg number and quality decrease over time. Female fertility peaks between a woman’s late teenage years through her late twenties. By 30, a woman’s ability to get pregnant starts to decline. This decline accelerates around age 35.^7,8 While you may have conceived earlier pregnancies easily, you were younger then. The natural decline in fertility may be contributing to secondary infertility.

7. Luteal Phase Defect

The luteal phase refers to the period of time between ovulation and your next period and should last between 12 and 14 days. During this time, the uterine lining is sustained by a hormone called progesterone secreted by the corpus luteum in the ovaries after ovulation. If progesterone is insufficient, the endometrium cannot sustain itself or support embryo implantation. Symptoms of luteal phase defect include spotting and a short luteal phase/early period.¹⁹ Tracking your cycle with natural family planning or fertility awareness methods can help to identify whether your luteal phase is of sufficient length to sustain a pregnancy. Progesterone supplementation and other medications can help lengthen the luteal phase for women trying to conceive. Luteal phase defect accounts for 3-4% of infertility cases.¹

8. Pelvic inflammatory disease (PID)

Pelvic inflammatory disease, which can result from sexually transmitted infections like gonorrhea or chlamydia, can cause scarring to the female reproductive tract, preventing or blocking the egg from being able to be released, fertilized, or carried to the uterus.²⁰

9. Scarring

Previous abdominal or pelvic surgery can cause scarring in the uterine cavity or reproductive tract. Surgeries, including cesarean section, dilation and curettage, and even appendectomy, can cause scarring and adhesions in the abdomen and uterus. If the adhesions are extensive, they can cause a thin uterine lining that would not support the implantation of an embryo.^12,21 These surgeries can also increase the risk of ectopic pregnancy.²¹ A symptom of this condition to look out for is reduced or absent menstrual blood flow. Adhesions or fibroids can also physically occlude the fallopian tubes or prevent implantation.¹⁵

10. Endometriosis

Endometriosis is a condition in which the lining of the uterus grows on the outside of the uterus or the surface of other abdominal organs.¹² It can cause painful periods, painful intercourse, chronic pain, and infertility. Endometriosis can also cause uterine scarring that contributes to infertility. It is thought that endometriosis contributes to 5% of infertility cases. It can be treated with surgery, and many women with endometriosis can get pregnant.¹

Male Factor Infertility

Male factor infertility accounts for about one-third of secondary infertility cases.¹² There is a misconception that infertility is a women’s issue, but male or combined factor infertility is just as likely. Some of the causes of male secondary infertility are described below.

1. Age

Women are not the only ones whose fertility is impacted by age. Male partners can also see a decline in fertility with age, but this usually does not happen until a man’s mid to late forties. Changes in a man’s sperm may cause issues with fertility and chromosomal conditions. If your partner is nearing this age, his sperm quality could be contributing to secondary infertility, even if you did not have difficulty conceiving in the past with the same partner.⁸

2. Varicocele

A varicocele is a cluster of enlarged veins in the testes that adversely affect sperm production. 15% of men have varicoceles, which are thought to be the most common cause of male infertility. About 35% of infertile males and nearly 70% of men with secondary infertility were found to have varicoceles.²² Varicocele prevalence increases over time, which may explain why more men with secondary infertility have them—because they are older than they were when they conceived their first babies.²³ There are several different methods of surgical varicocele repair, and many are successful in restoring adequate sperm quality for fertility.²²

3. Increased Scrotal Temperature

One theory on how varicocele affects male fertility is that a varicocele raises scrotal temperature, making the testes too warm to produce sperm.²⁴ External factors can also affect scrotal temperature, such as wearing briefs instead of boxers, using a laptop on your lap, or sitting for long periods, especially in a car. Luckily if your male factor infertility is caused by increased scrotal temperature, there are easy fixes to lower that temperature and make a difference in semen quality and quantity within a few months.²⁵

4. Unexplained Infertility

While one-third of secondary infertility is caused by the male partner and another third is caused by the female partner, combined or unknown causes cause the remaining third. Secondary infertility can be diagnosed as unexplained in about 20% of secondary infertility cases.⁵ Unexplained secondary infertility can bring with it its own frustrations when you are looking for answers and a potential treatment or path forward.

The good news is that since you were able to carry a first pregnancy, your odds of conceiving another child are 1.8 times greater than a couple experiencing primary infertility.²⁷ This is true even without being able to identify the cause of your secondary infertility. Many couples experiencing secondary infertility are successful in conceiving again if they keep trying. In fact, 95% of couples successfully conceive by the two-year mark of trying.²⁷ Despite the term “infertility,” this is not necessarily a permanent condition and does not always mean that you will never get pregnant again. Some medical literature refers to it as “secondary subfertility,” reflecting that although conception is taking longer than you would like, it is certainly not impossible.²⁷

Managing Your Emotions

Regardless of the statistics and the hope that exists for couples experiencing secondary infertility, your emotions, fears, frustrations, and anxiety are valid—just as valid as a couple with primary infertility. These emotions can cause a strain on your relationship and even cause sexual difficulties. Some find it embarrassing or stressful to disclose this situation, which prevents them from seeking medical or therapeutic help.⁴ However, there is nothing to be ashamed of if you are facing secondary infertility, and there are promising remedies to address many of the underlying causes.

If you are experiencing emotional distress related to secondary infertility, there are options to help. You could try support groups, individual and group therapy, confiding in a close, trusted family member or friend, or having candid conversations with your partner. There is hope in diagnosing and resolving the causes of your secondary infertility, but it is important to take care of yourself and your family in the meantime. Give yourself grace and empathy during this time. Secondary infertility is considered a medical disease that can be just as distressing as a cancer diagnosis. Do not be afraid to seek help if you feel defeated or feel that something is wrong.