Unexplained infertility is the name for not getting pregnant when the standard tests on both of you are normal. It is common, it is frustrating, and it has a clear set of next steps.

Unexplained infertility means you have not conceived after 12 months of regular unprotected sex, and the standard tests on both partners are normal.

It is a diagnosis made after testing, not a label for skipping it. It is common. It does not mean there is no reason; it means the reason is not one that routine tests can see, such as how well an egg and sperm work together.

Before infertility is called unexplained, four things should be checked: ovulation, the fallopian tubes, egg reserve and a semen analysis.

Ovulation is checked with cycle history, scans or a mid-luteal progesterone test. Tubes need an HSG or HyCoSy; a scan alone cannot show them. Egg reserve is AMH and an antral follicle count. His semen analysis is read against WHO limits. Thyroid and a pelvic scan are usually part of it too. If any of these was skipped, it is not yet unexplained.

Normal tests cannot see everything: egg quality, how sperm meet the egg, and mild endometriosis are common hidden reasons.

Age matters most, because egg quality falls with age even when AMH is normal. Time also counts: the longer you have tried, the lower the monthly chance without help. Weight, smoking and sleep affect both partners. None of this is anyone's fault.

The treatment for unexplained infertility is chosen by the woman's age and how long you have tried: more time trying, then IUI with ovarian stimulation, then IVF.

For some younger couples who have not tried long, more time is reasonable. IUI with tablets or low-dose injections is often the first active step. IVF comes sooner if you are older, have tried for years, or IUI has had its agreed number of cycles. Tablets alone with timed sex, without IUI, are not advised for unexplained infertility.

Neither is better for everyone: IUI is simpler and a reasonable start for younger women, while IVF gives more information and suits older women or longer trying.

IVF also shows how eggs and sperm behave together, which sometimes explains the 'unexplained'. That is useful, but it is not a reason to skip a fair trial of IUI when you are young. We agree the limit on IUI before you start.

The factor you can change most is lifestyle, led by a healthy weight, for both partners.

Regular sex every 2 to 3 days through the cycle works as well as timing it, with less pressure. Stop smoking, cut alcohol, and aim for about seven hours of sleep. Take folic acid. Get thyroid, blood sugar and vitamin D corrected if they are off.