Most women of reproductive age can get pregnant, but several measurable factors influence your chances in any given month. A woman in her early to mid-20s has roughly a 25 to 30% chance of conceiving per cycle, while by age 40 that drops to about 5%. Understanding where you fall on that spectrum involves paying attention to your body’s signals, getting a few targeted tests, and ruling out common obstacles.
Signs Your Body Is Ovulating
The most fundamental requirement for getting pregnant is ovulation, the monthly release of an egg from your ovaries. If you’re ovulating regularly, that’s a strong signal your reproductive system is working. Three signs you can track at home give you a practical read on whether ovulation is happening.
Cervical mucus changes: In the days before ovulation, your cervical mucus shifts from thick, white, and dry to clear and slippery, similar to raw egg whites. This consistency helps sperm travel to meet the egg. If you notice this pattern each cycle, it’s a good indicator that ovulation is approaching.
Basal body temperature (BBT): Your resting body temperature rises slightly, usually less than half a degree Fahrenheit, right after ovulation. To catch this shift, take your temperature every morning before getting out of bed using a digital thermometer, ideally at the same time each day after at least three hours of uninterrupted sleep. When the slight temperature increase stays steady for three or more days, ovulation has likely occurred. You’re most fertile in the two to three days before that rise, so BBT tracking works best after a few months of charting when you can predict your pattern.
Cycle regularity: A cycle that arrives roughly every 21 to 35 days suggests you’re ovulating. Cycles longer than 35 days apart, or fewer than 8 periods per year, point to irregular or absent ovulation, a pattern called oligo-amenorrhea that’s worth investigating.
How Age Affects Your Odds
Age is the single most predictive factor in natural fertility. In your early to mid-20s, you have a 25 to 30% chance of conceiving each month with well-timed intercourse. Fertility begins a gradual decline in the early 30s, and after 35 the drop accelerates. By 40, the per-cycle chance falls to around 5%. This decline reflects both a shrinking number of eggs and a higher proportion of eggs with chromosomal irregularities.
The American Society for Reproductive Medicine recommends that women under 35 who haven’t conceived after 12 months of trying seek evaluation, while women 35 and older should seek evaluation after just 6 months. These timelines exist because earlier intervention matters more when the window is narrowing.
Blood Tests That Measure Ovarian Reserve
Two blood tests give your doctor a snapshot of your egg supply, often called ovarian reserve. Neither tells you the quality of your eggs, but together they help estimate how your ovaries are likely to respond if you’re trying to conceive.
AMH (anti-Müllerian hormone): This hormone is produced by developing follicles in your ovaries and reflects the size of your remaining egg pool. In women under 35, the median level is about 2.55 ng/mL. In women 35 and older, the median drops to around 1.1 ng/mL. A very low AMH suggests fewer eggs are available, though it doesn’t mean pregnancy is impossible.
FSH (follicle-stimulating hormone): Measured on day 2 or 3 of your cycle, FSH tells your ovaries to develop an egg each month. When ovarian reserve is declining, your body produces more FSH to compensate, so higher numbers are less favorable. For women under 35, a typical median is around 5.8 IU/L. When FSH exceeds 10 to 12 IU/L, it generally signals low ovarian reserve.
Ultrasound Follicle Count
An antral follicle count (AFC) is performed via transvaginal ultrasound early in your cycle. The technician counts all small follicles (2 to 10 mm) visible on both ovaries. This count correlates directly with ovarian reserve and is one of the most practical predictors of your fertility potential.
An AFC above 13 is associated with meaningfully higher pregnancy rates. In one study, clinical pregnancy rates were 66% in women with an AFC above 13 compared to 37% in those below that threshold. An AFC of 10 or fewer is considered low and may indicate ovarian aging. A count of 9 or below identified poor ovarian response with about 84% specificity. Your doctor can pair the AFC with your AMH and FSH results to build a more complete picture.
Checking for Physical Blockages
Even with healthy ovulation and good egg supply, pregnancy requires a clear path for egg and sperm to meet. A hysterosalpingogram (HSG) is an X-ray procedure that checks whether your fallopian tubes are open. During the test, a contrast dye is injected into the uterus. If the dye flows freely through both tubes and spills into the surrounding area, the tubes are open. If the dye stops short, it signals a blockage.
The HSG also reveals the shape of the uterine cavity, catching structural issues like polyps or scar tissue that could interfere with implantation. The procedure takes about 15 to 30 minutes and can cause cramping similar to menstrual pain. It’s typically one of the first tests ordered during a fertility workup because tubal blockage accounts for a significant share of female infertility.
Conditions That Disrupt Ovulation
Polycystic ovary syndrome (PCOS) is one of the most common reasons women have trouble conceiving. It’s diagnosed when you meet at least two of three criteria: irregular or absent periods, elevated levels of male hormones (which can show up as acne or excess hair growth), and a characteristic appearance of the ovaries on ultrasound with many small follicles clustered around the edges.
The hallmark fertility issue in PCOS is infrequent ovulation. If you’re ovulating only a few times a year, you simply have fewer opportunities to conceive. The good news is that PCOS responds well to treatment, and many women with the condition go on to have successful pregnancies with lifestyle changes, medication to induce ovulation, or both.
Other conditions that can interfere with ovulation include thyroid disorders, elevated prolactin levels, and premature ovarian insufficiency (when the ovaries stop functioning normally before age 40).
Weight and Fertility
Body weight has a direct, measurable effect on ovulation. Women with a BMI of 32 or higher at age 18 have a 2.7 times greater risk of anovulatory infertility compared to women at a normal weight. Even in women who are ovulating, the chance of spontaneous conception drops by about 5% for each single-point increase in BMI above the normal range.
The sweet spot for fertility appears to be a BMI between 20 and 25. Women in that range have significantly higher odds of achieving pregnancy compared to those above 25. UK fertility guidelines recommend a BMI of 29 or lower as ideal for conception, and some clinics defer fertility treatment until BMI is below 35. Being significantly underweight (BMI below 18.5) can also disrupt ovulation by suppressing hormone production.
Your Partner’s Fertility Matters Too
About half of all infertility cases involve a male factor, so a semen analysis is a critical part of the picture. The test is simple and noninvasive: a sample is collected and evaluated in a lab. The World Health Organization sets baseline thresholds for what’s considered normal: at least 39 million sperm per ejaculate, total motility (sperm that are moving) of at least 40%, progressive motility (sperm swimming forward) of at least 32%, and normal sperm shape in at least 4% of the sample.
Falling below these numbers doesn’t mean pregnancy is impossible, but it does lower the odds per cycle and may call for further evaluation or treatment. A semen analysis is inexpensive and fast, so it makes sense to check early rather than spending months focused only on female factors.
Putting the Pieces Together
No single test or sign tells the whole story. A useful self-assessment starts with tracking your cycles for two to three months: Are they regular? Do you see the cervical mucus changes that signal ovulation? From there, age gives you a baseline expectation of your per-cycle odds. If you want a more detailed read, blood tests for AMH and FSH combined with an ultrasound follicle count can quantify your ovarian reserve. And if you’ve been trying without success, an HSG and semen analysis help rule out the structural and male-factor causes that are treatable once identified.
A sustained temperature rise lasting 18 days or more after ovulation, by the way, can itself be an early indicator of pregnancy. So the same tracking tools that help you assess fertility can also be the first to deliver good news.