If you’ve been trying to conceive without success, you’re not alone. Up to 15% of couples experience infertility, defined as not achieving pregnancy after 12 months of unprotected intercourse. The reasons range from timing and lifestyle factors to medical conditions affecting either partner, and in many cases, more than one factor is at play.
Your Fertile Window Is Shorter Than You Think
One of the most common reasons people don’t conceive right away has nothing to do with a medical problem. Even under ideal conditions, a healthy 30-year-old woman has only about a 20% chance of getting pregnant in any given cycle. That means even when everything is working perfectly, it can take several months.
The fertile window, the span of days when sex can actually lead to pregnancy, lasts roughly six days: the five days before ovulation and the day of ovulation itself. Sperm can survive inside the reproductive tract for three to five days, so sex in the days leading up to ovulation gives sperm time to be in position when the egg is released. If you’re only having sex after you think you’ve ovulated, you may be missing the window entirely. Ovulation predictor kits, basal body temperature tracking, or cervical mucus monitoring can help you identify the right timing more precisely.
Age Has a Significant Effect on Fertility
Fertility declines with age, and the drop is steeper than most people expect. By age 40, the chance of conceiving in any given cycle falls to less than 5%. By 43, even IVF success rates drop below 5%, and by 45, using donor eggs becomes the most realistic path to pregnancy for most women.
This decline happens because both the number and quality of eggs decrease over time. Women are born with all the eggs they’ll ever have, and as those eggs age, they’re more likely to have chromosomal abnormalities that prevent a healthy pregnancy. This is also why miscarriage rates rise with age. If you’re under 35 and have been trying for a year without success, or over 35 and have been trying for six months, it’s reasonable to seek a fertility evaluation. For women over 40, earlier evaluation is warranted.
Ovulation Problems Are a Leading Cause
If you’re not ovulating regularly, or not ovulating at all, pregnancy can’t happen. Polycystic ovary syndrome (PCOS) is one of the most common reasons for irregular or absent ovulation. PCOS involves a hormonal imbalance where the ovaries produce higher-than-normal levels of androgens (sometimes called “male hormones,” though everyone has them). This can prevent eggs from maturing and being released on a normal schedule. Signs include irregular periods, acne, excess hair growth, and difficulty losing weight.
Thyroid disorders can also disrupt ovulation. An underactive thyroid slows down many body processes, including the hormonal signals that trigger egg release. Thyroid problems are easily detected with a blood test and typically straightforward to treat, which often restores normal cycles.
Weight Affects Ovulation and Conception
Body weight plays a more direct role in fertility than many people realize. A BMI under 18.5 (underweight) often causes irregular periods and can stop ovulation entirely. On the other end, a BMI over 30 (obese) also disrupts menstrual cycles and ovulation. But weight affects fertility beyond just ovulation. Even women in the obese range who ovulate normally have lower pregnancy rates than women at a normal weight, suggesting that excess body fat influences fertility through additional pathways, likely involving inflammation and hormone metabolism.
A BMI between 19 and 24 is considered the normal range for fertility purposes. If your weight falls significantly outside that range, even modest changes (losing or gaining 5 to 10% of your body weight) can meaningfully improve your chances.
Blocked Fallopian Tubes
Your fallopian tubes are where egg meets sperm. If one or both tubes are blocked, that meeting can’t happen. The tricky part is that blocked tubes rarely cause noticeable symptoms, so many women don’t know there’s a problem until they have trouble conceiving.
The most common causes of tubal blockage are scar tissue and pelvic adhesions. These can result from pelvic inflammatory disease (often caused by untreated chlamydia or gonorrhea), endometriosis, previous abdominal or pelvic surgery, or a ruptured appendix. A test called a hysterosalpingogram, where dye is flushed through the uterus and tubes while an X-ray is taken, can show whether the tubes are open.
Endometriosis and Fertility
Endometriosis occurs when tissue similar to the uterine lining grows outside the uterus, most commonly in the pelvic cavity. During menstruation, this tissue behaves like it would inside the uterus: it thickens, breaks down, and bleeds. But because it has no way to exit the body, it causes inflammation, scarring, and adhesions that can damage the ovaries, fallopian tubes, and surrounding structures.
The impact on fertility goes beyond physical blockages. Women with endometriosis-related ovarian cysts (endometriomas) show reduced responsiveness to fertility treatments, retrieving fewer eggs and forming fewer embryos. Research suggests this isn’t just a local problem in the affected ovary. Studies on women with cysts on only one side found that both ovaries were affected, pointing to either undetected bilateral disease or a bodywide inflammatory effect. Painful periods, pain during sex, and chronic pelvic pain are the most recognizable symptoms, though some women with endometriosis have no symptoms at all.
Male Factor Infertility
In up to half of couples struggling to conceive, a male factor plays at least a partial role. Despite this, many couples focus exclusively on the female partner early on, which can delay answers significantly.
A semen analysis is the starting point. It measures three main things: sperm count (fewer than 15 million sperm per milliliter is considered low), motility (whether sperm swim well enough to reach the egg), and morphology (whether sperm are shaped normally). Common causes of poor semen quality include varicoceles (enlarged veins in the scrotum that raise testicular temperature), hormonal imbalances, prior infections, certain medications, and lifestyle factors like heavy alcohol use, smoking, or anabolic steroid use. A semen analysis is inexpensive and noninvasive, so it makes sense to do it early in the evaluation process rather than as an afterthought.
Lifestyle Factors That Add Up
No single lifestyle factor is likely to be the sole reason you’re not conceiving, but several together can meaningfully reduce your odds. Smoking damages eggs and sperm, reduces the success rate of fertility treatments, and is linked to earlier menopause. Heavy alcohol intake disrupts hormonal balance in both partners. High caffeine intake (more than about 300 mg per day, roughly two to three cups of coffee) has been associated with longer time to pregnancy in some studies, though the evidence is less definitive.
Chronic stress doesn’t directly prevent pregnancy in most cases, but it can disrupt ovulation by interfering with the hormonal signals from the brain to the ovaries. Extreme exercise, particularly in combination with low body weight, can have a similar effect by suppressing the reproductive hormone cycle. The takeaway isn’t that you need a perfect lifestyle to get pregnant, but that stacking several of these factors on top of each other can create a meaningful disadvantage.
Unexplained Infertility
After a full workup, roughly 10 to 15% of couples receive a diagnosis of unexplained infertility, meaning all standard tests come back normal but pregnancy still isn’t happening. This doesn’t mean nothing is wrong. It means the issue is beyond what current testing can detect, which could involve subtle problems with egg quality, sperm function, embryo implantation, or the immune environment of the uterus.
Unexplained infertility can be one of the more frustrating diagnoses to receive, but it doesn’t mean treatment can’t help. Many couples with unexplained infertility respond well to approaches like ovulation-stimulating medication combined with intrauterine insemination, or IVF. Success rates depend heavily on age and how long you’ve been trying, which is another reason not to delay evaluation if the standard timelines have passed.