If you’ve been trying to conceive without success, you’re not alone. About one in six couples experience difficulty getting pregnant, and the causes span a wide range of factors affecting both partners. The good news is that most of these factors are identifiable, and many are treatable. Understanding what might be working against you is the first step toward a solution.
How Long Is Normal Before Conceiving
Even under ideal conditions, conception doesn’t happen as quickly as many people expect. A healthy couple in their late twenties has roughly a 20 to 25 percent chance of conceiving in any given cycle. That means it commonly takes several months of well-timed attempts before a pregnancy occurs. In a large North American study tracking couples actively trying, about 79 percent of women aged 25 to 27 conceived within 12 cycles, while 77 percent of women aged 31 to 33 did the same. Those are encouraging numbers, but they also mean that roughly one in five couples in their early thirties won’t conceive within a full year of trying, and that can be completely normal.
The standard medical threshold for seeking a fertility evaluation is 12 months of regular unprotected intercourse for women under 35, and 6 months for women 35 and older. That shorter window for older women reflects the steeper decline in fertility that begins in the mid-to-late thirties.
How Age Affects Your Chances
Age is the single strongest predictor of natural fertility, particularly for women. The decline is gradual at first: women aged 28 to 30 have about 88 percent of the per-cycle conception probability of women in their early twenties. By 34 to 36, that drops to roughly 82 percent. The real inflection point hits after 37. Women aged 37 to 39 have about 60 percent of the cycle-by-cycle conception rate of younger women, and by 40 to 45, that figure falls to around 40 percent. At that age, only about 55 percent of women conceived within 12 cycles of trying.
This decline is driven primarily by egg quality and quantity. Women are born with all the eggs they’ll ever have, and both the number and the genetic integrity of those eggs decrease over time. Male fertility also declines with age, though more gradually. Sperm quality, motility, and DNA integrity all diminish in men over 40, contributing to longer time-to-pregnancy and higher miscarriage rates in their partners.
Ovulation Problems Are the Most Common Cause
Ovulatory dysfunction accounts for 25 to 40 percent of female infertility cases. If your body isn’t releasing an egg regularly, conception simply can’t happen. The most common culprit is polycystic ovary syndrome (PCOS), which is responsible for about 70 percent of all anovulatory infertility. PCOS disrupts the hormonal signals that trigger ovulation, often causing irregular or absent periods, excess androgen levels, and cysts on the ovaries.
Other causes of ovulation problems include hypothalamic dysfunction (where stress, extreme exercise, or very low body weight disrupts the brain’s hormonal signaling to the ovaries) and premature ovarian insufficiency, where the ovaries stop functioning normally before age 40. Thyroid disorders can also interfere with ovulation. The American Society for Reproductive Medicine recommends using your lab’s specific reference range for thyroid-stimulating hormone (TSH) when evaluating fertility, rather than applying pregnancy-specific thresholds before you’ve actually conceived.
If your cycles are irregular, very short, very long, or absent, that’s a strong signal that ovulation may not be happening consistently. Tracking your cycle length and using ovulation predictor kits can give you useful preliminary information before a formal evaluation.
Endometriosis and Structural Issues
Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, can sabotage fertility through multiple mechanisms at once. Adhesions and scar tissue distort pelvic anatomy, physically blocking egg release or pickup by the fallopian tubes. The condition also creates an inflammatory environment inside the pelvis: elevated inflammatory cells in the fluid surrounding the reproductive organs damage eggs and sperm directly, impair tubal function, and can even be toxic to early embryos.
Beyond these mechanical and inflammatory effects, endometriosis disrupts the hormonal environment needed for implantation. Progesterone receptor problems reduce the uterine lining’s receptivity to an embryo, and abnormal uterine muscle contractions can interfere with both the transport of sperm and egg and the implantation process itself. Oxidative stress in the endometrium further threatens embryo viability. All of this means that endometriosis can reduce fertility even when the tubes appear open and ovulation is occurring normally.
Blocked or damaged fallopian tubes from other causes, such as prior pelvic infections or surgery, account for another significant portion of structural infertility. Uterine fibroids and polyps, depending on their size and location, can also prevent implantation.
Male Factor Infertility
Male factors contribute to roughly half of all infertility cases, either alone or in combination with female factors. A semen analysis is one of the first tests that should be done, yet it’s often delayed because couples assume the issue is on the female side.
The World Health Organization defines normal sperm parameters as a concentration of at least 15 million sperm per milliliter, total motility of 40 percent or higher, and at least 4 percent normal morphology (shape). Falling below any of these thresholds doesn’t mean conception is impossible, but it does lower the odds per cycle. Common causes of poor sperm quality include varicoceles (enlarged veins in the scrotum that raise testicular temperature), hormonal imbalances, prior infections, certain medications, and lifestyle factors like heat exposure, smoking, and heavy alcohol use.
How Weight Influences Fertility
Body weight has a measurable impact on conception rates for both women and men. A systematic review and meta-analysis published in BMJ Open found that women with a BMI of 25 or higher were 24 percent less likely to achieve a clinical pregnancy compared to women at a healthy weight. For women with a BMI of 30 or above, the likelihood dropped by 39 percent. Higher BMI was also associated with a 32 percent increased risk of subfecundity, defined as taking longer than 12 months to conceive.
Excess body fat disrupts the hormonal balance needed for regular ovulation. It increases estrogen production, raises insulin levels, and can worsen conditions like PCOS. Being significantly underweight causes problems too: very low body fat can suppress the hormonal signals from the brain that drive the entire ovulatory cycle. For men, obesity is linked to lower testosterone, reduced sperm quality, and erectile dysfunction.
Even a modest weight change can make a difference. Losing 5 to 10 percent of body weight in overweight women has been shown to restore ovulation in many cases, while underweight women who gain enough to resume regular periods often see fertility return.
Alcohol, Caffeine, and Everyday Habits
Moderate caffeine intake doesn’t appear to significantly harm fertility. A large meta-analysis found no association between caffeine consumption and pregnancy or live birth rates. A cup or two of coffee a day is unlikely to be the reason you’re not conceiving.
Alcohol is a different story. Women who consume more than about 84 grams of alcohol per week (roughly six standard drinks) see a 7 percent reduction in pregnancy rates. For men at the same consumption level, their partners’ live birth rates drop by 9 percent. The effect is dose-dependent, meaning more alcohol correlates with worse outcomes. Cutting back or eliminating alcohol while trying to conceive is one of the simplest changes both partners can make.
Smoking is consistently harmful to fertility in both sexes. In women, it accelerates egg loss and damages the fallopian tubes. In men, it reduces sperm count, motility, and morphology. Chronic stress, poor sleep, and exposure to certain environmental chemicals (like those in some plastics and pesticides) also appear to play a role, though their individual effects are harder to quantify.
Unexplained Infertility
In about 15 to 30 percent of couples, standard testing doesn’t reveal a clear cause. This diagnosis, called unexplained infertility, doesn’t mean nothing is wrong. It means current testing can’t pinpoint the specific problem. Subtle issues with egg quality, sperm function, embryo development, or implantation may be at play but aren’t detectable with routine bloodwork, imaging, or semen analysis.
Couples with unexplained infertility still have reasonable chances of conceiving, both naturally and with treatment. Many go on to have successful pregnancies with relatively simple interventions like ovulation-stimulating medication combined with intrauterine insemination, while others move to in vitro fertilization, which bypasses many of the steps where things could be going wrong undetected.
What a Fertility Workup Involves
If you’ve hit the time threshold for your age group, a basic fertility evaluation typically covers several areas. For women, this includes blood tests to check hormone levels related to ovulation and ovarian reserve, imaging of the uterus and fallopian tubes (usually an X-ray-based test called a hysterosalpingogram), and sometimes a pelvic ultrasound. For men, the starting point is a semen analysis.
These initial tests identify the most common causes and help guide next steps. Depending on results, additional testing might explore thyroid function, genetic factors, or structural issues in more detail. The process can feel overwhelming, but most couples get actionable information from even the first round of testing. Knowing the cause, or narrowing down the possibilities, makes it far easier to choose the right path forward.