How Long Should It Take to Get Pregnant?

The honest picture, with numbers

The answer most people are given — "up to a year" — is technically true and practically useless, because it hides the shape of the distribution. Here is the shape.

NICE guideline NG257 states that over 80% of heterosexual couples in the general population conceive within 1 year where the woman is under 40 and they have regular unprotected vaginal intercourse without contraception. Of those who do not conceive in the first year, about half do so in the second year, giving a cumulative rate of over 90%.

Broken down by age, from data NICE reproduces for couples having intercourse about twice a week:

Per cycle, ACOG puts the chance at about 25% to 30% for healthy couples in their twenties and early thirties. That figure is worth sitting with, because it is far lower than most people assume. Even at peak fertility, roughly three cycles in four do not result in pregnancy. Three or four months of negative tests is the expected experience, not a warning sign.

And the corollary, which nobody says out loud: the average time to conception is several months, so the majority of people reading this at month four are entirely typical.

Why it takes as long as it does

Three things have to line up in the same cycle. An egg has to be released. Sperm has to be present in the reproductive tract in the days around that. And the resulting embryo has to be chromosomally viable and implant. The third is the biggest filter, and it is invisible — a substantial proportion of conceptions end before a period is even late.

This is why "we did everything right this month" and "it did not work" are not in contradiction. Timing controls the first two steps. Nothing controls the third.

What actually affects the timeline

NG257 sets out the factors with evidence behind them:

• Frequency. Vaginal intercourse every 2 to 3 days optimises the chance of pregnancy. This is the single most useful behavioural fact in the guideline, and it is deliberately not "on ovulation day" — regular frequency covers the fertile window without requiring you to identify it.
• Age. The dominant variable, as the table shows. NICE says to use age as the initial predictor of the overall chance of conceiving.
• BMI 30 or over. Associated with taking longer to conceive. Where ovulation is absent, weight loss is likely to increase the chance of conception, and a group programme with exercise and dietary advice leads to more pregnancies than advice alone.
• BMI under 18.5 with irregular or absent periods: increasing body weight is likely to improve the chance of conception.
• Smoking, including passive smoking, is likely to reduce fertility.
• Alcohol. NICE advises no more than 1 to 2 units once or twice a week and avoiding intoxication, noting the Chief Medical Officer's position that the safest approach is to avoid alcohol altogether. For men, drinking within 14 units a week spread across several days is unlikely to affect semen quality; excessive intake is detrimental.
• Caffeine. NICE states there is no consistent evidence of an association between caffeinated drinks and fertility problems.
• Medication. NICE specifically flags GLP-1 agonists, testosterone replacement, finasteride, NSAIDs, vaginal lubricants, anabolic steroids and cannabis as worth asking about.

Absent from that list, again, is stress. No guideline recommends calming down as a fertility intervention, because the evidence does not support one. If people around you keep offering that advice, it says more about their discomfort than about your chances.

What a normal few months actually looks like

Because the per-cycle chance is around 25% to 30% at best, the month-by-month experience of a completely typical couple looks like this: several negative tests in a row, at least one cycle where the period arrives a day or two late and raises hope, and a growing suspicion that something is wrong. That sequence is what an 86% one-year success rate feels like from the inside. The statistic and the experience are not in conflict.

Two further pieces of arithmetic help. First, the odds do not reset each month in your favour or against you — a negative cycle does not make the next one less likely. Second, the couples who conceive in month eleven are not doing anything different from the couples who conceived in month two; they are the same population, sampled later. There is no hidden technique separating them.

It is also worth knowing that a substantial share of conceptions end before a period is even late, which means some of the cycles you counted as "nothing happened" were cycles where something began and did not continue. That is not a failure of anything you did, and it is the main reason the process takes as long as it does.

What to do next

1. Aim for intercourse every 2 to 3 days rather than saving up for a predicted ovulation day. It is more effective and considerably less corrosive.
2. Track cycle length rather than symptoms. Regular monthly cycles mean you are likely to be ovulating, per NICE. Irregular or absent cycles are the flag worth acting on.
3. Start folic acid and check rubella immunity.
4. Set a review date rather than an open-ended wait. Decide now what month you will seek help in, based on the thresholds below, and put it in a calendar.

When to seek help

The WHO defines infertility as failure to achieve pregnancy after 12 months or more of regular unprotected intercourse. That is the baseline. The thresholds that determine what actually happens to you are:

• NICE (UK): after 1 year of unprotected vaginal intercourse, offer both partners further clinical assessment and investigation. Offer referral at first presentation if the woman is aged 36 or over, or if either partner has a known or suspected cause. If you are using artificial insemination, the threshold is 6 cycles.
• ACOG (US): evaluation after 12 months; after 6 months if older than 35; if older than 40, an evaluation is recommended before you start trying.
• Healthdirect (Australia): 12 months under 35, 6 months over 35, sooner with a known condition.

Go earlier than any threshold if you have irregular or absent periods, known PCOS or endometriosis, previous pelvic infection or chlamydia, previous cancer treatment, previous testicular surgery or undescended testes, or three or more miscarriages.

One more thing, in case you needed it in writing: about 1 in 7 couples in the UK have difficulty conceiving, and worldwide the WHO estimates around 1 in 6 people of reproductive age experience infertility in their lifetime. Whatever you are in the middle of, it is common, and it is not a referendum on you.