Getting pregnant depends on an egg and sperm meeting at the right time. Knowing how your cycle works helps you spot your most fertile days. Most couples do not need special tricks, just regular sex around ovulation and a little patience.
How your cycle works
A menstrual cycle starts on the first day of your period. The average cycle is about 28 days, but anything from 21 to 35 days is normal.
- PeriodThe lining of the womb sheds. This is day 1 of your cycle.
- Egg growsHormones help an egg mature in the ovary and the womb lining thickens again.
- OvulationThe egg is released, usually 10 to 16 days before your next period. In a 28-day cycle that is around day 14.
- After ovulationIf the egg is fertilised it may implant in the womb. If not, your next period starts.
Your fertile window
You can only get pregnant on a few days each cycle. An egg lives about 12 to 24 hours. Sperm can survive inside the body for several days, usually 3 to 5 and sometimes longer.
This means sex in the days before ovulation gives sperm time to be waiting when the egg is released. The window is usually the 6 days ending on ovulation day.
Fertile-window estimator
An estimate only, based on ovulation about 14 days before the next period. Nothing you enter is stored or sent.Calendars and calculators give an estimate only. If your cycles vary a lot, signs from your body or ovulation tests may help more.
Signs and tests for ovulation
| Method | What to look for |
|---|---|
| Ovulation test (LH kit) | A positive urine test means ovulation is likely within about 36 hours |
| Cervical mucus | Clear, slippery mucus like raw egg white in the days before ovulation |
| Body temperature | A small rise after ovulation; measure before getting out of bed |
| Cycle tracking | Ovulation is usually about 14 days before the next period |
Body temperature only rises after ovulation, so it confirms ovulation rather than predicting it. It is most useful for learning your pattern over several cycles.
Timing and frequency
The highest pregnancy rates are seen with sex every 1 to 2 days during the fertile window. If tracking feels stressful, having sex regularly through the whole cycle means you are less likely to miss it.
The NHS puts it simply: if you are 39 or under and have sex without contraception every 2 to 3 days, it is likely you will get pregnant within a year. You do not need to pinpoint the exact day.
- Have sex regularly, especially in the days before ovulation
- Keep up folic acid, a healthy weight and no smoking
- Use a fertility-friendly lubricant if you need one
- Worry about sex positions; none is proven to help
- Lie with your legs up for ages afterwards; it is not needed
- Save up sperm by avoiding sex for long stretches
Habits that help, and how long it takes
Your general health affects fertility for both partners. Smoking, heavy drinking and obesity can all make it harder to conceive, and they can affect eggs and sperm.
- Stop smoking and avoid recreational drugs, both of you
- Avoid heavy drinking and heavy caffeine use
- Take a daily folic acid supplement, plus vitamin D, before you conceive
- Aim for a healthy weight with good food and regular activity
Even with perfect timing, pregnancy does not happen every month. For women under 35 with regular cycles, about 20 to 37 in 100 conceive in the first 3 months, about 80 in 100 within a year, and about 90 in 100 within two years.
Trying for a baby can be stressful. If months go by, it is not anyone's fault, and getting checked early is a sensible step, not a failure.
When to get checked
Most couples simply need time. But waiting too long can matter, especially as age rises. ASRM advises an evaluation after a set time of trying, and sooner when there is a known reason for concern.
| Your situation | When to see a doctor |
|---|---|
| Woman under 35 | After 12 months of regular unprotected sex |
| Woman 35 or older | After 6 months of trying |
| Irregular or absent periods, past pelvic surgery or STI | Before you start trying, or now |
- Check whether your cervical screening test is due
- Have the MMR vaccine if you have not had it
- Talk to a doctor first if either of you lives with a condition such as epilepsy, diabetes, sickle cell disease or HIV
- Do not stop any prescribed medicine until you have talked to your doctor
Fertility checks are for both partners. A semen analysis for the man is simple and is usually done early, alongside the woman's tests.
Common myths
- Myth: certain positions help you conceive. There is no good evidence for this.
- Myth: any lubricant is fine. Some can affect sperm, so choose one made for couples trying to conceive.
- Myth: you ovulate on day 14. That is only true for some 28-day cycles.
- Myth: it should happen straight away. Many healthy couples take several months.
See a doctor before trying if your periods are irregular or absent, or you have had an STI or pelvic surgery.
When to see a doctor
- You are under 35 and not pregnant after 12 months of trying
- You are 35 or older and not pregnant after 6 months
- Your periods are irregular, very painful or absent
- You have had an STI or pelvic or abdominal surgery
Questions & answers
How long does it usually take?
More than 8 in 10 couples where the woman is under 40 conceive within a year of regular unprotected sex.
When should I start using ovulation tests?
Start a few days before you expect to ovulate and follow the kit instructions. A positive result means ovulation is likely within about 36 hours.
Do fertility apps work?
Apps help you record your cycle, but their predictions are estimates. Regular sex through the month is a simple back-up.
Related DBN services
Related articles
Sources
- Optimizing Natural Fertility — ASRM (ReproductiveFacts.org)
- Ovulation — Cleveland Clinic
- Periods and fertility in the menstrual cycle — NHS
- Infertility: diagnosis — NHS
- FAQ about infertility — ASRM (ReproductiveFacts.org)
- Trying to get pregnant / Planning your pregnancy — NHS