You've read the manuals, heard every ghoulish tale and swallowed the schoolgirl myths. But nothing quite prepares you for pregnancy, writes Sally Williams
Even though pregnant women today can write a birth plan, can tell parent-craft from pelvic floors, and know the difference between Sheila Kitzinger and Miriam Stoppard, there are still a multitude of things about being pregnant the books don't tell you. For instance ...

First Trimester (week 1 to 13)

A full-term pregnancy is not nine months: it's 40 weeks, more like 10 months (it can seem longer). Or, at least that is the medical measurement which dates pregnancy not from conception, but from the first day of your last period - which means even before you and your loved one have taken your clothes off, you are two weeks pregnant.

Morning sickness is really any time of the day. No, it doesn't always go away at around 14 weeks, and the mantra that most tomes chant as a cure - dry toast and a cup of tea before getting up - simply does not work.

Books list the cramping aches and pains which can herald a miscarriage, but mostly fail to mention the period-like pains that are common in the first three months. Due to the uterus stretching -the sign of a perfectly healthy pregnancy - these pains nevertheless convince many women that they are miscarrying.

The excesses of the period when you were pregnant, but didn't know it - the alcohol, soft cheese, dental X-rays and paracetamol - are obsessively worried over.

We all know that breasts start to anticipate their new function and become huge and granite-like. But did you know this sometimes occurs only hours after conception?

You are exhausted, even after 12 hours' sleep.

Second Trimester (week 14 to week 27)

Along with constipation and piles, hospital ante-natal visits become a leading "ailment of pregnancy". Average waiting time for an appointment: 2 hours 55 minutes.

Dreams become extraordinarily vivid. Common themes include being unprepared for the baby, going out and forgetting the baby, losing the baby, giving birth to a range of "babies" (from tiny brooch-sized ones to monsters), loving and playing with the "baby" (dog, doll, any inanimate object) and feeling enclosed or unable to escape.

About a third of women grow and glow when pregnant, a third feel the same and a third feel as sick as dogs.

Newsflash: stretch marks cannot be prevented by creams. You either get them or you don't. Creams, however, do help the itchy skin that can develop over the ever-expanding belly.

Books, hospitals and GPs all say that you should have ultrasound scans, Alpha-Foetoprotein screening, Chorionic Villi Sampling and blood tests. What they don't do is agree on when they should be done. This can result in the nagging feeling that your CVS should have been done at 16 and not 18 weeks, that you should already be on your second blood test and how safe are all these scans anyway?

Third Trimester (week 28 to birth)

Pants become a problem. Should they be worn below or above the bump?

Friends, relations and passers-by in the street feel compelled to tell you their birth experiences. These will be intriguing once you have delivered, but while you are pregnant, they're terrifying.

You fixate on the evils of dummies, instant baby food, antibiotics and disposable nappies. Note: this changes once the baby is born.

Women do not, repeat, do not, instinctively know when they are in labour. Many arrive at hospitals five minutes before birth wondering what that backache is all about. Others turn up two weeks early with nerves and indigestion.

You give birth. Not to a monochrome, two-dimensional abstract concept, but a whole, real baby. This is the biggest surprise of all.