If you’ve been trying to conceive without success, you’re not alone. Roughly one in six couples experience difficulty getting pregnant, and the causes split fairly evenly: about 40% of cases trace back to the female partner, 40% to the male partner, and the remaining 20% involve both partners or have no identifiable explanation. Understanding which factors could be affecting you is the first step toward doing something about it.
How Long Is Normal Before Conceiving
Healthy couples having regular unprotected sex have about a 15 to 25% chance of conceiving in any given cycle. That means even when nothing is wrong, it can take several months. The American Society for Reproductive Medicine defines infertility as the inability to conceive after 12 months of regular unprotected intercourse if you’re under 35, or after 6 months if you’re 35 or older. The shorter window for older women reflects the natural decline in egg quality and quantity that accelerates in the mid-30s.
If you haven’t hit those timelines yet, the odds may still be in your favor. But if you have reasons to suspect a problem, such as very irregular periods, a history of pelvic surgery, or a known condition like endometriosis, it’s reasonable to seek evaluation sooner rather than waiting out the clock.
Ovulation Problems
The most common female factor in infertility is irregular or absent ovulation. If your body isn’t releasing an egg consistently each month, conception becomes a matter of chance during the cycles when ovulation does occur.
Polycystic ovary syndrome (PCOS) is one of the leading causes. It affects an estimated 6 to 15% of women and is characterized by infrequent or prolonged periods, higher than normal levels of androgens (male hormones), and sometimes multiple small cysts on the ovaries. You might notice acne, excess facial or body hair, or thinning hair on your scalp. PCOS disrupts the hormonal signals that trigger ovulation, but it responds well to treatment in many cases.
Endometriosis is another major contributor. It affects up to 11% of women, and between 30 and 50% of women with the condition experience difficulty conceiving. Endometriosis occurs when tissue similar to the uterine lining grows outside the uterus, often on the ovaries, fallopian tubes, or pelvic lining. This can cause inflammation, scarring, and structural changes that interfere with egg release, fertilization, or implantation. Symptoms often include painful periods, pain during sex, and chronic pelvic pain, though some women have no symptoms at all.
Egg Supply and Ovarian Reserve
Every woman is born with a fixed number of eggs, and that supply declines steadily with age. By your mid-30s, both the quantity and quality of eggs drop more rapidly. This is one of the single biggest factors in fertility, and it affects women regardless of overall health.
Doctors often measure ovarian reserve using a blood test for anti-Müllerian hormone (AMH) and an ultrasound count of small follicles on the ovaries. Typical AMH levels drop from a median of about 4.2 ng/mL in the early 20s to around 2.4 ng/mL in the early 30s, 1.3 ng/mL in the late 30s, and 0.5 ng/mL by the early 40s. Levels at or below 1.1 ng/mL are generally considered low and may indicate a reduced response to fertility treatments. Values below the 10th percentile for your age suggest a higher risk of earlier-than-expected decline in fertility.
Low ovarian reserve doesn’t mean you can’t conceive, but it does mean the window may be narrower than average. If you’re concerned, AMH testing can give you a clearer picture of where you stand relative to others your age.
Male Factor Infertility
Male factors contribute to 40 to 50% of infertility cases, yet they’re frequently overlooked in early conversations about conception struggles. A semen analysis is one of the simplest and least invasive fertility tests available, and it should be part of any initial evaluation.
The World Health Organization considers a total sperm count below 39 million per ejaculate, total motility below 42%, or normal sperm shape in fewer than 4% of sperm to be below the threshold seen in men who achieved pregnancy within a year. Low numbers in any of these areas don’t automatically mean infertility, but they do reduce the odds per cycle.
Common contributors to poor sperm quality include varicoceles (enlarged veins in the scrotum), hormonal imbalances, prior infections, certain medications, and lifestyle factors like heat exposure to the testicles from prolonged laptop use or hot tub use. Sperm production takes about 72 days, so changes you make today can show up in a semen analysis roughly three months later.
Blocked or Damaged Fallopian Tubes
Even when ovulation and sperm quality are normal, conception requires that the egg and sperm can physically meet. Blocked or damaged fallopian tubes prevent this. Causes include prior pelvic infections (especially chlamydia or gonorrhea, which can be asymptomatic), previous abdominal or pelvic surgery, and endometriosis-related scarring.
Tubal patency is typically checked with a hysterosalpingogram (HSG), an X-ray procedure where a contrast dye is gently pushed through the uterus and tubes. If the tubes are open, the dye flows through and spills out the ends, visible on the X-ray. The test takes about 10 to 15 minutes and can cause cramping similar to period pain. An alternative is a sonohysterosalpingogram, which uses saline and air bubbles viewed on ultrasound instead of X-ray dye. Both tests also reveal abnormalities inside the uterus, such as polyps or fibroids, that could interfere with implantation.
Lifestyle Factors That Affect Fertility
Weight plays a measurable role. Higher BMI in women is associated with longer time to conception, a greater likelihood of needing fertility treatment, and a slightly increased risk of miscarriage. Being significantly underweight can also disrupt ovulation by suppressing the hormones needed to trigger it. A BMI between roughly 19 and 25 is generally considered the range where reproductive hormones function most reliably.
Smoking has a clear negative effect. Women who smoke take longer to conceive, and the effect has been confirmed through both observational and genetic studies. In men, there’s weaker but suggestive evidence that smoking increases time to conception as well. Alcohol’s impact is less clear-cut. Large studies have found that moderate drinking doesn’t significantly affect time to conception in women, though there’s some evidence it may have a small effect in men. Heavy or binge drinking is a different story and is best avoided when trying to conceive.
Vitamin D status also appears to matter. Women with PCOS or those who are overweight may benefit from 2,000 to 4,000 IU of vitamin D daily, based on current clinical guidelines. Maintaining a blood level of 30 to 50 ng/mL is the target recommended for women planning pregnancy. If you’re unsure of your levels, a simple blood test can check.
Secondary Infertility
If you’ve had a successful pregnancy before and are now struggling, you’re experiencing what’s called secondary infertility. It’s actually more common than primary infertility. In one large study, 56% of patients seeking fertility care had conceived before.
The causes overlap with primary infertility (age, ovulation issues, sperm quality), but a few factors are more prominent. Women with secondary infertility are significantly more likely to have had previous surgery, particularly cesarean delivery, which can cause pelvic adhesions that compromise the normal anatomy of reproductive organs. Age is also a factor: women with secondary infertility tend to be older on average, and even a gap of two or three years can matter when egg quality is declining. Uterine abnormalities, whether from scarring, fibroids that developed over time, or changes from a prior pregnancy, are among the most frequently documented causes.
Unexplained Infertility
About 30% of infertile couples worldwide receive a diagnosis of unexplained infertility, meaning all standard tests come back normal but pregnancy still isn’t happening. This can be one of the most frustrating outcomes of a fertility workup, but it doesn’t mean nothing can be done.
Unexplained infertility likely reflects subtle issues that current testing can’t detect: minor problems with egg quality, sperm function at the molecular level, embryo implantation, or the immune environment of the uterus. The good news is that many couples with this diagnosis do eventually conceive, either on their own or with relatively straightforward interventions like ovulation-stimulating medication combined with timed intercourse or intrauterine insemination. Success rates with these approaches are generally encouraging, particularly for women under 38.
What a Basic Fertility Workup Looks Like
A standard evaluation typically includes a few core tests. For the female partner: blood work to check hormone levels (including AMH and thyroid function), an ultrasound to look at the ovaries and uterine lining, and an HSG or sonohysterosalpingogram to assess the fallopian tubes. For the male partner: a semen analysis. These tests can usually be completed within one or two menstrual cycles and give a clearer picture of where the problem, if any, lies.
Some results lead to specific treatments. Blocked tubes, for instance, may point toward IVF. Ovulation disorders often respond to medication. Low sperm counts might improve with lifestyle changes or could warrant intrauterine insemination. The value of the workup is replacing uncertainty with a plan, even if the plan is simply “keep trying with better timing.” Knowing what you’re working with is almost always better than guessing.