In the past few years, I've seen a number of patients wanting to know how they can choose the sex of their baby.

Reports from different experts around the world have aroused hopes and expectations -- and many parents-to-be have come into the surgery convinced that they'll be able to have a boy or a girl with hardly any chance of an error.

The truth is, of course, it isn't possible to provide a 100 per cent sure way of ensuring that a couple get the baby they want. .

But there are lots of people who claim to know of methods which improve the odds a little from the normal 50 per cent chance.

Hazel Phillips, for example, worked out a formula that. she claimed has a success rate of over 80 per cent. She described her method in a book called Girl or Boy? that she wrote a few years ago with Tessa Hilton.

According to Hazel, the first thing you have to do is work out when ovulation takes place. There are various ways of doing this, but the simplest is probably to remember that ovulation normally takes place 14, days before the next period starts.

It is possible to get a more accurate idea of when ovulation takes place by plotting daily temperatures -- but that can be rather tedious and time-consuming.

If you want a boy, then you should abstain from intercourse until the day of ovulation. If you want a girl, then you should have sex from the beginning of the cycle until three days before ovulation when you should avoid intercourse.

Neither Hazel Phillips nor I guarantee that this method will work. But it will at least be fun trying!

All this interest in choosing the sex of a baby has reminded me of a doctor I used to know years ago. He had a foolproof way of predicting the sex of a baby.

When a pregnant woman went to see him and wanted to know what sex her baby was going to be, he would tell her that she was going to have a girl; and he would write a note in the back of his diary. Just so that there wouldn't be any argument about it afterwards.

But being a crafty old doctor he would write 'boy' in the back of his diary.

When the patient came to see him after the birth, he would be able to claim a 100 per cent success rate. If she had a girl, then she'd probably remember what he'd told her. And he wouldn't need the diary.

If she had a boy, then he'd take out his diary, show her the entry, and explain that she must have misheard him!