For most people, the best known treatment for infertility is, without a doubt, in vitro fertilisation. It is never far away from the news headlines, not least because of the many new treatments which have followed in it's wake. But when a couple first have fertility problems, the way they are treated will not always involve IVF.

For many couples, simple changes in lifestyle can make conception possible. Smoking, drinking, being very overweight or very underweight, eating an unhealthy diet and lacking folic acid in the diet can also make it difficult or impossible to conceive. For a surprising number of people, a change in lifestyle can result in the birth of a baby.

One of the most common ways of treating fertility problems involves fertility drugs. These are not only remarkably successful in their own right, but have also paved the way for the development of IVF. One of the main reasons women fail to get pregnant is because they do not produce mature eggs. Fertility drugs are chemicals which work in different ways to stimulate the woman's body to produce and release a mature egg from the ovary.

The most widely used drug is clomiphene citrate. This drug works by fooling the body into making extra FSH and so stimulating the production of eggs by the ovaries. When women do not make any of their own FSH they can be given different drugs which actually contain human hormones. These stimulate the ovary directly. Other fertility drugs can be used if the mature eggs are not released from the ovaries.

The use of these drugs has been very successful in helping many infertile couples to have children, and they have also been vital in the development of IVF.

Three's a crowd?

Fertility drugs have helped many infertile couples to have children, but when they were first developed they caused problems of their own. In the early days of fertility drugs doctors were not always sure of the doses to use, and many of the women using the drugs had multiple pregnancies - in other words, more than one egg was released and fertilised at the same time. Twins did not cause too many problems, but far more people than expected had triplets, quads or even more babies.

American figures show that around 24 sets of twins for every 1000 births in the population as a whole. In comparison, about 200 sets of twins are born for every 1000 couples treated with fertility drugs - a big increase - and the risk of bigger multiple pregnancies increases in a similar way.

Large multiple pregnancies cause many problems. When lots of babies are all developing in the same uterus, there is an increased risk that labour will start very early as the uterus becomes hopelessly overstretched, and very tiny babies, born very early, are quite likely to die or become brain damaged. So for a number of couples, the joy of finally becoming pregnant using fertility drugs was followed by the crushing grief of losing some or all of their much-longed for babies.

It would be easy to think that someone desperate for a baby would welcome an instant family of three, four or more children, but it is not quite that simple. If lots of babes arrive at once the demands on the parents, both physically, mentally and financially , can be enormous. What is more, the demands of looking after a large family last for many years, long after the interest and excitement of the local media has died away!

It also costs society a great deal of money in care for tiny premature babies.

So multiple pregnancies, particularly more than twins, are now avoided if at all possible. With increased knowledge of the way fertility drugs work and close control of the dosage large multiple pregnancies are now very rare indeed.