IT'S a woman's dream come true. An almost foolproof contraceptive without the nasty side-effects of the pill but with all the benefits - and at a lower cost.

The Mirena levonorgestrel-releasing intra-uterine system (IUS) is the best contraceptive to date, according to renowned Professor of Reproductive Medicine Ian Fraser of the University of Sydney.

'Virtually any woman from the age of 13 can benefit from this. It is a wonderful alternative to sterilisation and a great solution for those suffering from heavy or painful menstruation,' says the professor.

A study by KK Women's and Children's Hospital (KKH), the results of which were released at the recent Mirena Forum in Singapore, showed that almost half of women who opt for sterilisation will regret doing so.

'Whenever women come to me for tubal ligation I inform them that it is a permanent procedure,' says Dr Loh Seong Feei, head and senior consultant of the reproductive medicine unit at KKH's division of obstetrics and gynaecology.

The hospital performs about 900 sterilisations a year.

Not irreversible

According to Prof Fraser: 'Women who opt for sterilisation often do so because they feel they have completed their families and no longer want more children. But sterilisation does more than that, in fact - it completely cuts a woman off from her reproductive life, and psychologically it may affect her self-esteem.'

With the Mirena, women do not take such an irreversible step. It leaves a window open for those who change their minds later.

The Mirena acts as a contraceptive by making the mucus at the neck of the womb - the cervix - much thicker, preventing sperm from getting through. It also makes the lining of the womb very thin, stopping implantation. In some women, it prevents ovulation altogether.

'The IUS is good for five years,' says Prof Fraser. 'It is a localised hormonal contraceptive method, meaning only a very minimal amount of hormone is circulated in the bloodstream. And, because of this, there are far less systemic side-effects compared with other forms of contraception.'

What's more, Bayer Schering's Mirena IUS costs about $600, which works out to quite a bit less than if a woman goes on the pill. Introduced here in 1992, some 2,500 women go on the Mirena each year.

Insertion takes only 10 minutes and women who have given birth previously should not feel much discomfort. For those who haven't, a local anaesthetic may be administered.

Removal is a simple process - all a doctor need do is pull on some strings. This is only uncomfortable for a few seconds as the device comes out. The hormonal effect on the lining of the womb is usually reversed after a month or so and fertility returns.

It is not just older women who can benefit from this contraceptive.

'Most intrauterine devices or IUDs make a women's period heavier, but the Mirena makes it lighter,' points out Prof Fraser. 'In fact, it almost completely switches off the blood, and bleeding can be reduced by up to 90 per cent. This is wonderful for those who suffer from very heavy periods or those who are anaemic.'

About a third of women stop menstruation completely after a year on the Mirena. One study of women awaiting hysterectomy because of heavy periods showed about 70 per cent of the 54 women on the waiting list dropped out after using the Mirena.

According to Prof Kristina Gemzell-Danielsson from Sweden's Karolinska Institutet, fibroids are one cause of heavy periods.

'We have found that fibroids are less common in women who use the Mirena,' she says. 'While the Mirena isn't actually used as a treatment for fibroids, this is yet another benefit for those on it.'

No issue of compliance

The Mirena also works well for those with premenstrual syndrome.

'PMS is caused by varying hormones of the menstrual cycle,' explains Prof Fraser. 'The IUS allows a continuous dose of hormones to be given without worrying about excessive stimulation of the womb's lining.'

And, unlike the pill, there is no issue of compliance, he says. 'You won't even feel it and there's no need to constantly think about it. In this sense, it is very convenient.'

There will be some spotting in the initial months, though, and a very small number of women may develop acne after prolonged use, but the benefits clearly outweigh the mild side-effects.

Already, new directions are being planned, and the Mirena may prove useful for those suffering from other gynaecological disorders, such as endometriosis.

But here's the really good news. For young women who are sexually active and wish to avoid unplanned pregnancy, the Mirena is almost foolproof as a contraceptive, with a failure rate much lower than other IUDs or the pill.

If 1,000 women use the Mirena for a year, only one will fall pregnant. This compares with about 10 for traditional IUDs and 20 for the pill. In effect, it is as good as sterilisation.

This story was first published in The Business Times on Mar 15, 2008.