For most couples, getting pregnant is easier than you might expect. About 75% of couples conceive within six months of trying, and roughly 90% conceive within a year. But that still leaves a meaningful number of people who struggle, and several factors can shift your odds significantly in either direction.
What the Numbers Actually Look Like
Each menstrual cycle gives you a relatively narrow window to conceive. An egg survives less than 24 hours after release, and sperm can live inside the body for up to five days. That means you have roughly six fertile days per cycle, and even with perfectly timed sex, the per-cycle chance of pregnancy tops out around 20 to 25% for women in their early twenties.
Those odds feel low on a monthly basis, but they compound quickly. Among all age groups combined, about 75% of couples conceive within six months and 90% within a year. By two years, 95% have conceived. So for the majority of people, getting pregnant isn’t especially hard. It just takes longer than many expect, and a few months of negative tests is completely normal.
How Age Changes the Timeline
Age is the single biggest factor affecting how quickly you’ll conceive, and the decline is more gradual than many people realize until it accelerates sharply in the late thirties. A large North American preconception study tracked thousands of women actively trying to get pregnant and found the following cumulative pregnancy rates after 12 cycles of trying:
- Ages 21 to 24: about 71%
- Ages 28 to 30: about 78%
- Ages 34 to 36: about 75%
- Ages 40 to 45: about 56%
Notice that fertility stays relatively stable through the early thirties. The per-cycle probability at 28 to 30 is roughly 88% of what it is at 21 to 24, a modest difference. At 34 to 36, it’s about 82% of the younger group’s rate. The real drop happens after 37. By 40 to 45, per-cycle odds fall to about 40% of what a woman in her early twenties would experience. For women 35 to 39 trying without assistance, about 60% conceive within one year and 85% within two years.
This doesn’t mean pregnancy after 40 is impossible. More than half of women in that age range in the study did conceive within a year. But the timeline stretches, and the chance of needing medical help rises.
Common Reasons It Takes Longer
When couples do struggle, the cause is split fairly evenly between male and female factors. Male fertility issues are the sole cause in about 20% of cases and a contributing factor in another 30 to 40%, meaning men play a role in roughly half of all infertility. This is worth knowing because fertility conversations often focus exclusively on women.
On the female side, the most common medical barrier is polycystic ovary syndrome (PCOS), which disrupts ovulation and accounts for nearly half of female-factor infertility cases. Blocked or damaged fallopian tubes, often caused by past pelvic infections, are another significant cause. Conditions like endometriosis and thyroid disorders also interfere with conception. In a sizable number of cases, no clear cause is ever identified, which is frustrating but doesn’t necessarily mean treatment won’t work.
Lifestyle Factors That Shift Your Odds
Your daily habits have a measurable effect on how quickly you conceive. One study tracked couples trying naturally over 12 months and counted how many “adverse lifestyle factors” each couple had, things like smoking, heavy drinking, obesity, and high caffeine intake. The results were striking: 83% of couples with zero adverse factors conceived, compared to just 38% of couples with four.
Smoking is particularly damaging on both sides. In men, it reduces sperm quality and increases DNA damage in sperm cells, with heavier smokers seeing worse effects. In women, smoking disrupts ovarian function, depletes egg reserves, and can bring menopause one to four years earlier than it would otherwise occur. It even changes the outer shell of the egg in ways that make it harder for sperm to penetrate.
Alcohol’s effect is more nuanced. There’s limited evidence that light or moderate drinking harms female fertility on its own, but heavier consumption is linked to worse outcomes, particularly during fertility treatment. One study of women undergoing IVF found that those who drank alcohol retrieved fewer eggs, were nearly three times less likely to achieve pregnancy, and had more than double the risk of miscarriage. In men, increasing alcohol consumption is associated with lower testosterone, lower sperm counts, and reduced sperm motility.
Weight plays a role too. Being significantly overweight or underweight can disrupt hormone cycles and ovulation. The modern pattern of delaying pregnancy for education and career goals often means people are both older and heavier when they start trying, which compounds the challenge.
When to Start Asking Questions
The American Society for Reproductive Medicine recommends a straightforward timeline. If you’re under 35 and have been trying for 12 months without success, it’s reasonable to seek a fertility evaluation. If you’re 35 or older, that window shortens to 6 months. For women over 40, a more immediate evaluation makes sense given the steeper decline in per-cycle odds.
These timelines aren’t arbitrary. They’re calibrated to the point where the probability of conceiving without help drops low enough that investigating potential causes is more productive than continuing to wait.
What Fertility Treatment Can Do
If you do end up needing help, the success rates for IVF have improved significantly. Based on 2022 data from the Society for Assisted Reproductive Technology, the live birth rate per egg retrieval cycle breaks down by age:
- Under 35: 53.5%
- 35 to 37: 39.8%
- 38 to 40: 25.6%
- 41 to 42: 13.0%
- Over 42: 4.5%
Those are per-cycle numbers. Many people undergo more than one cycle, so cumulative success rates over multiple attempts are higher. For women under 35, the per-cycle success rate of over 50% represents a dramatic improvement over even a decade ago. The steep age-related decline still applies, though, reinforcing why earlier evaluation matters for older couples.
IVF isn’t the only option. Depending on the cause, treatments can range from medication that stimulates ovulation to minor surgical procedures that clear blocked tubes. For many couples, these less intensive approaches are enough. IVF is typically reserved for cases where simpler methods haven’t worked or where the underlying cause requires it.