If you’ve been having regular unprotected sex and haven’t conceived, you’re not alone. About one in eight couples has difficulty getting pregnant. The reasons range from hormonal imbalances to structural issues to lifestyle factors, and in many cases, more than one thing is contributing at the same time. Understanding the most common causes can help you figure out what to investigate first.
How Long Is Normal Before Conceiving
Timing matters more than most people realize. Even with perfect health and well-timed intercourse, the odds of conceiving in any single menstrual cycle are only about 15 to 25 percent. That means it can take several months of trying before pregnancy happens, and that’s completely normal.
The general guidance is that women under 35 with regular cycles should try for at least one year before seeking medical evaluation. If you’re 35 or older, that window shortens to six months. Women over 40 should consider evaluation sooner, since egg quality and quantity decline more steeply in this age range. These aren’t arbitrary cutoffs. They reflect how quickly fertility changes with age and how much earlier intervention can improve outcomes.
Ovulation Problems
The single most common reason women struggle to conceive is that ovulation isn’t happening regularly, or at all. Without the release of an egg each cycle, there’s simply nothing for sperm to fertilize.
Polycystic ovary syndrome (PCOS) is the leading cause of ovulation problems. In PCOS, the ovaries produce higher than normal levels of androgens (often called “male hormones,” though all women produce them in small amounts). Those elevated androgens prevent the ovaries from releasing eggs, which is why irregular or missing periods are one of the hallmark signs. Many women with PCOS also have insulin resistance, where the body needs more insulin than usual to manage blood sugar. That extra insulin signals the ovaries to produce even more androgens, creating a cycle that suppresses ovulation further.
Thyroid disorders can also disrupt ovulation. Both an overactive and underactive thyroid interfere with the hormonal signals that trigger egg release. The same is true of elevated levels of prolactin, a hormone normally involved in milk production, which can suppress ovulation even when you’re not breastfeeding. These hormonal causes are often treatable once identified.
Blocked or Damaged Fallopian Tubes
Your fallopian tubes are where sperm meets egg. If one or both tubes are blocked or scarred, sperm can’t reach the egg, or a fertilized egg can’t travel to the uterus. This accounts for roughly 25 to 30 percent of female infertility cases.
Pelvic inflammatory disease (PID), usually caused by untreated chlamydia or gonorrhea, is one of the most common culprits. The infection causes inflammation near the fallopian tubes, leading to scar tissue and blockages. You can have had PID without knowing it, since it sometimes causes mild or no symptoms. Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, can also scar or block the tubes. Prior abdominal or pelvic surgery is another risk factor.
Tubal problems are typically diagnosed with an imaging test that pushes dye through the tubes to check for blockages. Depending on the severity, treatment ranges from surgical repair to bypassing the tubes entirely with IVF.
Uterine Issues
Even when an egg is fertilized and travels successfully to the uterus, it still needs to implant in the uterine lining. Growths inside the uterus can physically interfere with that process.
Fibroids, which are noncancerous muscle tumors, are extremely common. Not all fibroids affect fertility, but location matters. Submucosal fibroids, which grow on the inside of the uterus, and intramural fibroids, which develop within the uterine wall, can obstruct an embryo from implanting and increase the risk of miscarriage. Large fibroids of any type can distort the shape of the uterine cavity enough to cause problems. Uterine polyps, which are smaller growths on the lining itself, can similarly prevent a fertilized egg from attaching correctly. Both fibroids and polyps are detectable with ultrasound or a specialized scope inserted through the cervix.
Male Factor Infertility
About a third of infertility cases involve a male factor, either alone or alongside a female factor. Low sperm count, poor sperm movement, or abnormally shaped sperm all reduce the chances of fertilization. Yet many couples initially focus only on the woman’s health, which can delay diagnosis by months.
A semen analysis is a simple, early test that should be done alongside any female evaluation. Causes of male infertility include varicoceles (enlarged veins in the scrotum that overheat the testicles), hormonal imbalances, prior infections, certain medications, and genetic factors. Lifestyle factors like heavy alcohol use, smoking, and anabolic steroid use also reduce sperm quality significantly.
Age and Egg Quality
Female fertility begins declining gradually in the early 30s and drops more sharply after 35. This isn’t just about having fewer eggs. The eggs that remain are more likely to have chromosomal abnormalities, which makes fertilization less likely and miscarriage more common. By 40, the chance of conceiving naturally in any given cycle is roughly 5 percent.
Male fertility also declines with age, though more gradually. Men over 40 tend to have lower sperm quality and slightly higher rates of genetic abnormalities in their sperm. Age on both sides of a couple matters.
Weight and Fertility
Body weight has a direct, measurable effect on ovulation. A BMI below 18.5 (underweight) often causes irregular cycles and can shut down ovulation entirely. The body essentially decides conditions aren’t favorable for pregnancy and stops releasing eggs. On the other end, a BMI of 30 or higher (obese) also disrupts menstrual cycles and ovulation, partly through its effects on insulin and hormone levels.
The good news is that weight-related ovulation problems are often reversible. For women who are underweight, gaining even a modest amount of weight can restart regular cycles. For women with a higher BMI, losing 5 to 10 percent of body weight has been shown to meaningfully improve ovulation rates. A BMI between 19 and 24 is associated with the most regular ovulation patterns.
Other Lifestyle Factors
Smoking reduces fertility in both men and women. In women, it accelerates the loss of eggs and damages the fallopian tubes. In men, it lowers sperm count and motility. Heavy alcohol consumption has similar effects, disrupting hormone levels and reducing the chances of conception per cycle.
Chronic stress doesn’t directly “cause” infertility in the way a blocked tube does, but prolonged high stress can interfere with the hormonal signals that regulate ovulation. Extreme exercise, particularly when combined with low body weight, can suppress your reproductive hormones enough to stop ovulation. This is common in endurance athletes and women with very low body fat percentages.
Unexplained Infertility
In about 10 to 15 percent of cases, all standard tests come back normal and no clear cause is found. This diagnosis, called unexplained infertility, doesn’t mean nothing is wrong. It means the available tests haven’t identified the issue. Possible explanations include subtle egg quality problems, sperm function issues that don’t show up on a standard semen analysis, or implantation difficulties that current technology can’t detect.
Couples with unexplained infertility still have treatment options. Many respond well to fertility medications that stimulate ovulation, intrauterine insemination, or IVF. Success rates depend heavily on age and how long you’ve been trying.
What a Fertility Workup Looks Like
If you’ve reached the point where evaluation makes sense, expect testing for both partners. For women, the process typically starts with blood tests measuring hormones that control ovulation: follicle-stimulating hormone (FSH), luteinizing hormone (LH), estrogen, and progesterone. These are usually drawn at specific points in your menstrual cycle. Your doctor may also check thyroid levels and a hormone called anti-Müllerian hormone (AMH), which gives an estimate of your remaining egg supply.
Imaging comes next. An ultrasound can reveal fibroids, polyps, ovarian cysts, and signs of PCOS. A test called a hysterosalpingogram uses dye and X-ray to check whether the fallopian tubes are open. For men, a semen analysis is the starting point. If results are abnormal, further hormone testing or imaging may follow. The key principle is that both partners should be evaluated at the same time rather than sequentially, since treating only one partner’s issue when both contribute wastes valuable time.