Apps, kits and discharge: which ones can you trust?

Usually about 14 days before your next period starts, so the day depends on the length of your cycle.

In a 28-day cycle that is around day 14. In a 24-day cycle it is closer to day 10, and in a 35-day cycle closer to day 21. The fertile window is the 6 days ending on the day of ovulation, because sperm can survive for several days and the egg lives for about a day. Ovulating earlier than day 13 in a short cycle is usually a normal variation. What matters is that you ovulate, not the day number.

Discharge and LH kits tell you ovulation is coming; a temperature rise tells you it has already happened.

As ovulation nears, discharge becomes clear, wet, slippery and stretchy, like raw egg white. The chance of conceiving is highest on the days it looks like this. Urine LH kits pick up the hormone surge that comes before ovulation, and ovulation usually follows within 12 to 36 hours. A basal body temperature chart shows a small rise after ovulation, so it confirms rather than predicts. Other signs, such as one-sided twinges, breast tenderness or bloating, vary too much to rely on.

An app that only knows your period dates is making an estimate from past cycles, not detecting ovulation.

Apps are useful for recording your periods and seeing your pattern. But they cannot see this month's hormones, so a late or early ovulation, a fever, travel or stress will not show. Apps that take in your discharge notes or kit results are more useful than period dates alone. Paid wearables and multi-hormone monitors cost more, and the evidence that they add much for couples trying to conceive is limited.

Start testing about 2 days before you expect ovulation, test at the same time each day, and read it exactly as the leaflet says.

For a 28-day cycle, many women start around day 11; start earlier if your cycles are shorter. On most strips, a positive result means the test line is as dark as the control line or darker; a faint line is negative. Avoid drinking a lot of water in the two hours before testing, because dilute urine can hide the surge. Simple strips work on the same hormone as digital kits. In PCOS, LH can be high much of the month, so kits can mislead.

No. Sex every 2 to 3 days through the month works almost as well as sex on the exact fertile days.

Sex every day or every other day in the fertile window gives the highest chance, but 2 to 3 times a week is nearly as good. That matters, because timing every month can drain the pleasure out of sex and add strain between you. Lying down afterwards, or a particular position, makes no difference. If tracking is making you anxious, it is fine to stop and simply keep having sex regularly.

Then home tracking will not answer the question, and a doctor can check whether you ovulate.

Irregular cycles often mean ovulation is irregular too, from causes such as PCOS, thyroid problems, raised prolactin, weight change or low egg reserve. A progesterone blood test about a week before your expected period shows whether you ovulated, and follicle-tracking scans show an egg growing and being released. Most ovulation problems are treated with tablets and scans, not IVF. Remember that tracking checks only one thing: it cannot see the tubes, the womb or the sperm.