If you and your girlfriend have been trying to conceive without success, you’re not alone. About 1 in 6 couples experience difficulty getting pregnant. The general guideline is that if a woman under 35 has been having regular unprotected sex for a full year without conceiving, it’s worth looking into possible causes. For women 35 and older, that window shortens to six months. The reasons range from timing and lifestyle factors to medical conditions in either partner, and in many cases, the issue is identifiable and treatable.
It Might Not Be About Her
Male factors contribute to roughly half of all infertility cases, either alone or in combination with a female factor. A semen analysis is one of the first and simplest tests in a fertility workup. The World Health Organization considers a healthy sample to contain at least 39 million sperm per ejaculate, with more than 32% actively moving forward. But no single sperm measurement is a reliable predictor of fertility on its own. The odds of infertility climb as multiple parameters fall outside normal ranges together.
In some cases, sperm count is zero, a condition called azoospermia. Heavy alcohol intake also plays a measurable role: men who drink roughly 32 or more standard drinks per week show a 33% reduction in sperm concentration compared to light drinkers. Heat exposure, certain medications, hormonal imbalances, and varicoceles (enlarged veins in the scrotum) can all affect sperm production or quality. The point is that a fertility issue is never assumed to be one partner’s problem. Both of you should be evaluated.
The Most Common Female Causes
Polycystic ovary syndrome, or PCOS, is the single most common cause of female infertility. It creates a hormonal imbalance that disrupts ovulation, meaning the ovaries don’t reliably release an egg each month. PCOS is closely linked to insulin resistance and often shows up alongside weight changes, acne, or unusual hair growth. Many women don’t realize they have it until they start trying to conceive.
Endometriosis is another frequent culprit. Tissue similar to the uterine lining grows in places it shouldn’t, causing inflammation and scarring that can block the fallopian tubes or interfere with an embryo implanting. Even mild endometriosis can reduce fertility in ways that aren’t fully understood, including possible damage to eggs and sperm.
Blocked or damaged fallopian tubes prevent sperm from reaching the egg or stop a fertilized egg from traveling to the uterus. This damage often results from pelvic infections, prior surgeries, or endometriosis. Hormonal disruptions from the brain’s signaling system can also shut down ovulation. Extreme stress, very high or low body weight, and rapid weight changes can all throw off the hormones that trigger egg release each cycle.
Timing Matters More Than You Think
Even when everything is working perfectly, the window for conception each month is surprisingly narrow. A woman can only get pregnant during about six days per cycle: the five days before ovulation and the day of ovulation itself. The highest odds, around 30%, come from having sex on the day of ovulation or the two days just before it. Five days before ovulation, the probability drops to about 10%. Six or more days before ovulation, the chance is essentially zero. And within 12 to 24 hours after ovulation, the egg is no longer viable.
This means that couples who have sex regularly but consistently miss that fertile window may struggle to conceive despite having no medical issues at all. Ovulation doesn’t always happen on the same day each cycle, especially for women with irregular periods. Tracking ovulation through home test kits, basal body temperature, or cervical mucus changes can help you identify the right days with more precision.
Age and Egg Supply
A healthy, fertile 30-year-old woman has about a 20% chance of getting pregnant in any given month. By 40, that drops below 5%. This decline reflects two things happening simultaneously: the number of eggs remaining in the ovaries decreases, and the quality of those eggs declines. Unlike sperm, which are produced continuously, women are born with all the eggs they’ll ever have.
A blood test measuring anti-Müllerian hormone (AMH) can estimate how many eggs remain. This is called ovarian reserve. A low AMH level doesn’t necessarily mean pregnancy is impossible, but it does signal that the window may be shorter and that fertility treatment might require adjusted approaches. Importantly, AMH tells you about egg quantity, not quality. There’s currently no definitive test for egg quality.
When No Cause Is Found
Between 10% and 30% of couples who undergo a full fertility workup receive a diagnosis of unexplained infertility, meaning all standard tests come back normal. This doesn’t mean nothing is wrong. It means current testing can’t detect the issue. Possible hidden factors include subtle egg or sperm quality problems that don’t show up on standard analyses, cervical mucus that’s too thick for sperm to travel through, undiagnosed conditions like celiac disease or thyroid disorders, or even mild endometriosis that hasn’t been identified.
Unexplained infertility can be frustrating, but it doesn’t mean treatment won’t work. Many couples in this category respond well to fertility medications, intrauterine insemination, or other assisted reproductive techniques.
Lifestyle Factors Worth Addressing
Body weight affects fertility in both directions. Being significantly overweight or underweight can disrupt the hormonal signals that control ovulation. For men, obesity is associated with lower testosterone and reduced sperm quality. Even moderate weight changes in either direction can sometimes restore normal ovulation or improve sperm parameters.
Smoking damages fertility for both partners. In women, it accelerates egg loss and can interfere with implantation. In men, it reduces sperm count and motility. Alcohol has measurable effects as well, particularly at higher intake levels. Recreational drug use, excessive caffeine, and chronic sleep deprivation can also play a role. None of these factors guarantee infertility, but addressing them removes obstacles that could be tipping the balance.
What Testing Looks Like
For women, a fertility evaluation typically starts with blood tests to check hormone levels, including AMH to estimate egg supply and other hormones to confirm whether ovulation is occurring. An ultrasound can show the ovaries and uterus, and a specialized imaging procedure can check whether the fallopian tubes are open. For men, the first step is a semen analysis, which measures sperm count, movement, and shape. If the count is very low (under 10 million per milliliter), hormone testing and sometimes genetic testing may follow.
These tests aren’t painful or invasive for most people, and they can usually be completed within one or two menstrual cycles. Getting answers early gives you more options, especially if age is a factor.