Female infertility is the inability to become pregnant after at least one year of regular, unprotected sex, or after six months if you’re over 35. It affects a significant number of people: the World Health Organization estimates that roughly one in six people of reproductive age worldwide experience infertility at some point in their lives. The causes range from hormonal imbalances to structural problems in the reproductive tract, and in a surprising number of cases, no clear cause is found at all.
How Female Infertility Is Defined
The one-year and six-month timelines aren’t arbitrary. They reflect how long it realistically takes most couples to conceive, even when nothing is wrong. Healthy couples having regular sex have about a 20 to 25 percent chance of conceiving in any given cycle, so it can take several months of trying before pregnancy occurs. The shorter six-month window for women over 35 exists because egg quality and quantity decline with age, and earlier evaluation means less time lost.
Doctors also distinguish between two types. Primary infertility means you’ve never been pregnant. Secondary infertility means you’ve had at least one prior pregnancy but are now unable to conceive again. Secondary infertility is often unexpected and can be just as difficult to diagnose, since prior success doesn’t guarantee future fertility.
Ovulation Problems
The most common category of female infertility involves problems with ovulation, the monthly release of an egg from the ovaries. If ovulation doesn’t happen regularly, or doesn’t happen at all, there’s no egg available to be fertilized.
Polycystic ovary syndrome (PCOS) is one of the most frequent culprits. In PCOS, a hormonal imbalance prevents the ovaries from releasing eggs on a normal schedule. When ovulation doesn’t occur, the ovaries can develop many small fluid-filled sacs that produce excess androgens (sometimes called “male hormones,” though all women produce them in small amounts). Many women with PCOS also have insulin resistance, meaning their bodies don’t use insulin efficiently. Insulin levels rise, which can drive androgen levels even higher and further disrupt ovulation. Carrying extra weight can worsen insulin resistance and amplify these effects, creating a cycle that’s hard to break without treatment.
Other ovulation disruptions include primary ovarian insufficiency, where the ovaries stop functioning normally before age 40, and hormonal imbalances involving the thyroid or the pituitary gland. Even high levels of stress or significant changes in body weight can temporarily shut down ovulation.
Structural and Anatomical Causes
Even when ovulation is working perfectly, physical barriers in the reproductive tract can prevent pregnancy. These fall into two main categories: problems with the fallopian tubes and problems with the uterus.
The fallopian tubes are where sperm meets egg. If one or both tubes are blocked or damaged, that meeting can’t happen. Blockages are often caused by pelvic inflammatory disease (usually from untreated sexually transmitted infections), prior abdominal surgery, or endometriosis. Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, can cause scarring and inflammation that distorts the tubes or interferes with egg pickup.
Inside the uterus, fibroids (noncancerous growths in the uterine wall), polyps, and scar tissue can all prevent a fertilized egg from implanting properly. Asherman’s syndrome, a rare condition where scar tissue forms inside the uterus after surgery or infection, can create physical blockages that make pregnancy impossible without treatment.
Unexplained Infertility
In 10 to 30 percent of couples trying to conceive, standard fertility tests come back normal and no clear cause is identified. This is called unexplained infertility, and it’s one of the most frustrating diagnoses to receive.
That doesn’t mean nothing is wrong. It means current testing methods aren’t sensitive enough to detect every problem. Mild endometriosis, for instance, can contribute to infertility even when it causes no obvious symptoms, and it’s only definitively diagnosed through surgery. Subtle issues with cervical mucus can prevent sperm from reaching the egg. Conditions like celiac disease, diabetes, or thyroid disorders may quietly interfere with fertility in ways that aren’t immediately obvious. Sometimes the issue is simply timing: if the frequency or timing of sex doesn’t line up with ovulation, conception won’t happen regardless of how healthy both partners are.
Age and Egg Quality
Age is the single most important factor in female fertility, and it’s the one that can’t be reversed. Women are born with all the eggs they’ll ever have. Both the number and quality of those eggs decline steadily over time, with a sharper drop after the mid-30s. By age 40, the chance of conceiving naturally in any given cycle is significantly lower than at 30, and the risk of miscarriage rises because older eggs are more likely to have chromosomal abnormalities.
This is a biological reality, not a judgment. It’s also why fertility specialists recommend earlier evaluation for women over 35 who haven’t conceived after six months.
How Infertility Is Diagnosed
A fertility evaluation typically begins in the first few days of your menstrual cycle. Your doctor will order blood work to measure key hormones: FSH (follicle-stimulating hormone), estradiol, and AMH (anti-Mullerian hormone). Together, these give a picture of your ovarian reserve, essentially how many eggs you have left and how well your ovaries are responding to reproductive signals. A transvaginal ultrasound counts the small follicles visible on your ovaries, which provides another measure of reserve.
To check whether your fallopian tubes are open, a procedure called a hysterosalpingogram (HSG) is commonly used. A small amount of contrast dye is injected through the cervix and into the uterus while X-ray images are taken. If the dye flows freely through both tubes, they’re open. If it stops, that points to a blockage. The procedure takes about 15 to 30 minutes and can cause cramping similar to menstrual pain.
Your doctor may also evaluate the uterine cavity for fibroids, polyps, or structural abnormalities using ultrasound or a specialized scope. If PCOS or a thyroid condition is suspected, additional hormone panels will be ordered.
Treatment Options
Treatment depends entirely on the cause. For ovulation disorders like PCOS, medications that stimulate ovulation are usually the first step. These are taken orally or by injection and work by prompting the ovaries to release one or more eggs. Cycle monitoring with ultrasound and blood work helps time intercourse or insemination for the best chance of success.
For blocked fallopian tubes, surgery to repair or open the tubes is sometimes possible, though success rates vary depending on where the blockage is and how much damage exists. In many cases, in vitro fertilization (IVF) bypasses the tubes entirely by fertilizing the egg in a lab and transferring the resulting embryo directly into the uterus. IVF is also the primary option when other treatments haven’t worked, when multiple factors are involved, or when age is a significant concern.
Fibroids and polyps that distort the uterine cavity can often be removed surgically, which may improve the chances of implantation. Endometriosis may be treated with surgery to remove tissue growths, though the condition can recur.
For unexplained infertility, treatment often follows a stepwise approach: ovulation-stimulating medication combined with timed intercourse, then intrauterine insemination (where sperm is placed directly in the uterus), and then IVF if simpler methods don’t succeed. Many couples with unexplained infertility do eventually conceive, though it can take longer and require more intervention than expected.
Lifestyle Factors That Affect Fertility
While lifestyle changes alone won’t overcome structural problems or significant hormonal disorders, they can meaningfully improve your odds, especially when combined with medical treatment. Maintaining a healthy weight matters in both directions: being significantly underweight or overweight can disrupt ovulation. For women with PCOS, even modest weight loss (5 to 10 percent of body weight) can restore regular cycles in some cases.
Smoking accelerates egg loss and damages the reproductive tract. Heavy alcohol use and excessive caffeine intake have both been linked to reduced fertility, though moderate amounts are generally considered low-risk. Chronic stress doesn’t “cause” infertility in the way people sometimes suggest, but it can suppress the hormonal signals that trigger ovulation, particularly when severe or prolonged.