Helping an egg release

Women whose periods are irregular or absent and whose progesterone test shows that ovulation is not happening, once the look-alikes have been ruled out and treated: a thyroid or a prolactin level put right sometimes restarts ovulation by itself, and in PCOS a modest change in weight often does. The tubes should be known to be open, or at least there should be no reason to think they are not, and his count should be adequate, because tablets that release an egg achieve nothing if the egg cannot be reached.

It is not for the woman who is already ovulating regularly and has been for years; for her the tablets add little, and the reason for not conceiving lies elsewhere.

Letrozole is now the usual first choice. Taken for five days early in the cycle, from about day two or three, it briefly lowers oestrogen, which makes the body send a stronger signal to the ovary to grow a follicle. It tends to grow one follicle rather than several, which is what is wanted, and it does not thin the lining of the uterus. Clomiphene is the older tablet and works a different way to the same end; it is still used, and for some women it is the better fit. Which one, and at what dose, is decided from your tests and adjusted from what the first cycle’s scans show.

Metformin is sometimes added for women with PCOS whose tests show the body handling insulin poorly. It is not a fertility tablet on its own and it is not for everyone.

A scan around day ten to twelve of the cycle shows whether a follicle has grown and how big it is. Sometimes a second scan a few days later. When the follicle reaches the right size, ovulation follows within a day or two on its own, or an injection is given to time it precisely. Intercourse is timed to that window, at home, and you are told exactly which days. A progesterone test a week later confirms that the egg was released.

The scans are what make this a treatment rather than a guess. Tablets taken without them can go on for months without anyone knowing whether they worked, and that is time lost.

Because the tablets ask the ovary for more than it would do alone, occasionally two follicles grow instead of one, and a twin pregnancy becomes possible. That is exactly what the scan is for: if too many follicles have grown, you are told, and that cycle is stopped rather than risked. With letrozole and careful scanning a twin pregnancy is uncommon, and a triplet pregnancy should not happen.

Two different things can go wrong, and they are handled differently. If the scan shows that no follicle grew, the dose is raised in the next cycle, and if that fails, the drug is changed. If the scans show that an egg was released and the cycle still did not lead to a pregnancy, the tablets are working and what is needed is time, or, after a fair run, the next step. A small number of women do not respond to either tablet, and for them the next step, injections or IUI, is discussed early rather than after months of the same thing.