How many IUIs before IVF? Our limits, by age.

It depends mainly on her age and egg reserve: more cycles are reasonable when she is younger with good reserve, fewer from 35, and fewer again from 38.

We agree the number with you before the first IUI and write it into your plan. Then every IUI has a reason, and the move to IVF is a planned step, not a panic after months of trying. The limit is shorter if the egg reserve is low or endometriosis is severe. Dr Vani's limits are below, in her words.

Because egg numbers and egg quality fall with age, so every month spent on a treatment that is not working costs more after 35.

From the mid-30s, and faster after 40, more eggs carry chromosome errors that stop an embryo growing. IUI cannot change egg quality, and neither can IVF. What IVF can do is collect several eggs in one cycle and show how they fertilise and grow. Time spent on extra IUIs is time the eggs keep ageing, which is why the limit gets shorter as she gets older.

When a test shows IUI cannot work: both tubes blocked, low egg reserve, severe endometriosis, or a sperm problem too severe for IUI.

IUI needs at least one open tube, because the egg and sperm still have to meet inside the body. It also needs enough moving sperm after washing; with a severe sperm problem, IVF with ICSI is usually the route. The UK regulator (HFEA) lists blocked tubes, severe endometriosis, low egg reserve, poor egg quality and male factor infertility as reasons IUI is not appropriate. This is why both of you are tested before any IUI.

With unexplained infertility, IUI with ovarian stimulation is a reasonable first step, within the age limit.

The European guideline (ESHRE, 2023) recommends IUI with ovarian stimulation as first-line treatment for unexplained infertility, and says IVF is probably not better as a first step. It also says the choice should depend on her age, how long you have tried and past treatment. Stimulation is kept gentle and watched by scan, and a cycle is stopped if too many follicles grow, to avoid triplets or more.

Often nobody can tell from an IUI cycle alone, because IUI does not show whether the egg and sperm met, fertilised or grew.

The egg and sperm may not have met, because of a subtle tube problem or mild endometriosis. They may have met without fertilising. The egg may have carried a chromosome error, which becomes more common with age. Or the timing may have been slightly off. IVF answers some of these questions, because fertilisation and early growth happen where we can see them. It also carries its own limits: it cannot improve egg quality.

IVF means daily injections for about 8 to 12 days, egg collection under anaesthesia and embryos grown in the lab, so it asks more of you in time, cost and feeling.

We explain every step and give you the plan in writing before you start. Costs are given in writing too, before you commit, including what might be added and why. It is normal to feel disappointed that IUI did not work. Talk about it with each other, and with our counsellor if it helps. [CONFIRM: counsellor]