If you haven't heard by now that two of the Spice Girls are pregnant, then you must have just dropped in from Mars. They are also said to be suffering from pregnancy cravings - or pica. Let's hope they are fairly easy ones to cope with. Not like toxic sock syndrome.

No it's not a misprint for toxic shock. It's an illness reported in a pregnant woman who couldn't stop eating the wool from socks. She ate so much wool that she developed the human equivalent of a fur ball in her stomach. She needed surgery to unblock it. Think that must be an extreme case? Then what about the ante-natal patient who wandered into the post-natal ward to see a friend for an hour or two - and who quietly ate the rubber bungs from the ends of the baby's cot sides? It was only when she needed help a few days later that we learned where the bungs had gone! She became "bunged up" in more senses than one!

There's also cigarette pica. The ciggies aren't smoked, but devoured with relish. And the women won't change to herbal cigarettes: it seems they needed the nicotine and tobacco taste. And eating earth - from the garden or pot plants - isn't too uncommon. Everyone has heard, too, about the woman who ate coal during pregnancy. I can't confirm any true cases of that, although I know of women who were put off the idea by licking a piece!

The amazing thing is that very few women actually come to any harm from indulging in pica. Especially when we read, from an American Dietetic Association report, the list of the commonest types of pregnancy pica during pregnancy in 281 young women. Top were ice and freezer frost, followed by baking soda, baking powder, corn starch, laundry starch, baby powder, clay and soil.

What was interesting about that report was that the women with pica were anaemic - their blood iron levels were much lower than similar pregnant women with no pica. The authors suggest that family doctors who find that their pregnant patients are anaemic ask them about pica - and treat the anaemia accordingly. Many women are too embarrassed to talk about it unless they are asked directly about it.

Of course most pregnancy cravings don't involve strange materials, but just an overwhelming appetite for a particular food - probably one the woman wouldn't normally bother with. For most women, that is restricted to something everyday, like pickled onions or chocolates.

But one woman took to lasagna and custard - on the same plate - every day. From the day her baby was born she has never been able to look at either without feeling a bit sick!

And there was the woman who wanted chocolate doughnuts throughout the pregnancies that produced her sons, and raspberry ripple ice cream in those that produced her daughters. She got furious if anyone wanted to share her ice-cream!

This "foody" version of pica doesn't seem to be linked to iron deficiency

but to changes in hormone sensitivities in the brain. It doesn't always

produce a craving - it can also make you grue at a particular food or smell that would normally be attractive. One woman hasn't been able to stand the smell of roast pork since her last pregnancy 20 years ago. Another hates the smell of geraniums - which she used to love.

We don't know for sure why these changes happen, and why some seem to be permanent, and others stop as soon as the child is born. What isn't in doubt is that most women who have them are normal mentally, and there doesn't seem to be any reliable treatment to reverse it, if it does continue after the pregnancy is over. It may just take time.

Pica isn't restricted to pregnancy. It can be a real bother in children, especially in those with learning difficulties. Of course, small children often eat strange things, but they usually have stopped by their third year. Pica that starts after that time may be linked to coeliac disease

- in which an allergy to gluten (it's found in flour) can interfere with normal digestion.

But the weirdest medical paper on pica comes from Sweden. Doctors there asked, not entirely tongue in cheek, whether Dracula suffered from pica!

After all, if you are anaemic, what better cure could there be but blood. If only the heroic Professor van Helsing had known that, he could have saved the world a lot of trouble - by sending his vampire enemies a big box of iron tablets.

Converted for the new archive on 30 June 2000. Some images and formatting may have been lost in the conversion.