Infertility is defined as the failure to achieve a pregnancy after 12 months or more of regular, unprotected sexual intercourse. That 12-month mark is the standard clinical threshold, but it shifts based on age: if the female partner is 35 or older, evaluation is recommended after just 6 months of trying. About one in six couples worldwide will experience infertility at some point, and the causes split roughly into equal thirds between male factors, female factors, and a combination of both or unknown origins.
The 12-Month and 6-Month Timelines
The one-year benchmark exists because most fertile couples will conceive within that window. Each month of trying carries roughly a 15 to 25 percent chance of pregnancy for couples in their twenties and early thirties, so 12 months gives enough cycles for conception to happen naturally if everything is working as expected. When it doesn’t happen in that timeframe, something is likely interfering.
For women 35 and older, the timeline shortens to 6 months. This isn’t arbitrary. Egg quality and quantity decline more steeply after 35, and the success rates of fertility treatments also decrease with age. Starting evaluation sooner preserves more options. The American Society for Reproductive Medicine specifically recommends this accelerated timeline even when neither partner has a known reproductive issue.
Primary vs. Secondary Infertility
Primary infertility refers to couples who have never achieved a pregnancy. Secondary infertility describes couples who have been pregnant before (whether or not the pregnancy resulted in a live birth) but are unable to conceive again. Secondary infertility is surprisingly common and can be confusing for people who assumed that a previous pregnancy meant they wouldn’t have trouble in the future. The causes are often the same as primary infertility: age-related changes, new hormonal imbalances, or conditions that have developed since the last pregnancy.
Common Causes in Women
Female infertility generally falls into a few major categories. Ovulation problems are among the most frequent. If you have irregular or absent periods, your ovaries may not be releasing eggs consistently. Conditions like polycystic ovary syndrome are a leading cause of irregular ovulation.
Tubal factor infertility accounts for 25 to 30 percent of all infertility cases. This happens when a blockage in one or both fallopian tubes prevents the egg and sperm from meeting. The blockage can result from past pelvic infections, endometriosis, or previous surgeries. Sometimes only one tube is blocked or scarring has narrowed the tubes without completely closing them, which can reduce fertility without eliminating it entirely.
Uterine abnormalities, including fibroids, polyps, or structural irregularities, can also interfere with implantation. And endometriosis, where tissue similar to the uterine lining grows outside the uterus, affects fertility through inflammation, scarring, and sometimes direct damage to the ovaries or tubes.
Male Factor Infertility
Male reproductive issues account for roughly one-third of infertility cases on their own and contribute to another third where both partners have a factor. Despite this, many couples initially assume the problem is on the female side. A semen analysis is the first and most important test for the male partner. It measures sperm count, movement, and shape. Low sperm count, poor motility (sperm that don’t swim well), or abnormal sperm shape can all reduce the chances of fertilization.
Causes of male infertility range from varicoceles (enlarged veins in the scrotum that raise testicular temperature) to hormonal imbalances, genetic conditions, and lifestyle factors like smoking, heavy alcohol use, or exposure to certain chemicals. In some cases, prior infections or surgeries are responsible.
When to Seek Evaluation Earlier
Certain signs and conditions warrant a fertility evaluation before the standard 6 or 12-month mark. If you have very irregular or absent periods, that alone suggests ovulation may not be happening reliably. A history of endometriosis, pelvic inflammatory disease, or previous ectopic pregnancy increases the risk of tubal damage. Painful periods, especially pain that worsens over time or pain during sex, can point toward endometriosis.
For men, a history of testicular surgery, cancer treatment, or known low testosterone levels are reasons to get checked sooner. And for any couple where either partner has a known condition that affects reproductive function, waiting the full timeline isn’t necessary or helpful.
What the Initial Evaluation Looks Like
For women, the evaluation typically starts with a blood test around day 21 of the menstrual cycle to confirm whether ovulation is occurring. If your cycles are irregular, the timing of this test gets adjusted accordingly, sometimes repeated weekly until your period arrives. An imaging test called a hysterosalpingogram checks whether the fallopian tubes are open and whether the uterus has a normal shape. This involves injecting a small amount of dye and taking X-rays to watch it flow through the reproductive tract. Women with risk factors for tubal blockage, like a history of endometriosis or pelvic infections, may instead be offered a more detailed procedure using a small camera.
For men, the process is simpler. A semen analysis is the starting point, collected after 48 to 72 hours of abstinence from ejaculation. This single test provides a significant amount of information about whether male factor infertility is playing a role.
Unexplained Infertility
Up to 30 percent of couples who complete a standard fertility evaluation receive a diagnosis of unexplained infertility. This means ovulation is confirmed, at least one fallopian tube is open, and the semen analysis looks adequate, yet pregnancy still isn’t happening. It’s a frustrating diagnosis because there’s no specific problem to fix. Treatment in these cases is empiric, meaning doctors try approaches that are known to improve conception rates in general rather than targeting a specific cause. Options typically start with less invasive methods and escalate from there based on how you respond and how much time you’re comfortable spending at each stage.
Unexplained infertility doesn’t mean nothing is wrong. It means the standard tests haven’t detected the issue. Subtle problems with egg quality, sperm function at the cellular level, or the interaction between sperm and egg can all be difficult to measure with current testing. For many couples with this diagnosis, fertility treatments are still effective.