Ovulation tablets work when a scan checks them.

Ovulation induction is treatment with tablets or low-dose injections that helps the ovary grow one mature follicle and release an egg.

It is for women who ovulate rarely or not at all, most often because of PCOS. It can also help women with very irregular cycles for other reasons, once thyroid and prolactin problems are ruled out. The aim is modest on purpose: one egg, released at a time we can see.

For women with PCOS who are not ovulating, international guidelines recommend letrozole as the first tablet, because it leads to more live births than clomiphene.

Letrozole briefly lowers oestrogen, so the brain releases more of the hormone that grows follicles. Clomiphene can thin the womb lining in some women; letrozole usually does not. Clomiphene is still an option when letrozole doesn't suit you. Both are taken for about 5 days early in the cycle.

Scans show whether the tablets worked: how many follicles grew, how big they are, and whether the lining is ready.

Without a scan, nobody knows if you ovulated, when, or whether three follicles grew instead of one. That is how months pass on tablets with no answer. We usually scan 2 or 3 times around day 8 to 14, and adjust the dose next cycle from what we see.

If the sperm test is normal and at least one tube is open, timed intercourse on the days the scan shows is usually the first step.

IUI is added when the sperm count is mildly low, intercourse is difficult, or timed cycles haven't worked. Sometimes a trigger injection is used to release the egg at a known time. [CONFIRM: Jananam's routine] The choice depends on age, sperm results, tubes and how long you've tried.

Usually up to about six cycles in which you ovulate, and fewer if you are older or also need IUI. [CONFIRM: Dr Vani's limit]

If you ovulate and are not pregnant after those cycles, more of the same rarely helps. If you don't ovulate even at the right dose, the plan changes sooner: low-dose injections, IUI, or IVF. The limit is agreed at your first visit, not after a year of tablets.

It can, because tablets sometimes grow more than one follicle, and that is the main risk of ovulation induction.

Twins carry real risks for mother and babies, including early birth. Scans are how we see it coming: if too many follicles grow, we advise you not to try that month and adjust the dose next time. Hot flushes, headaches and bloating are common, mild side effects.