Anyone who has ever heard two new mothers or fathers talking about "The Birth" would be amazed that there is any mystery left in the process. My experience is that parents are only too keen to share their uncensored birth stories. One new father insisted on telling me (long before I had children of my own) about his wife's Caesarean section. Over my weak protests, he described the event in visceral detail, and only stopped talking - at least, I presume he did - when I crashed to the floor in a faint.

With information available from the internet, books, magazines, not mention other parents, it seems extraordinary that a single detail of the process of conceiving, delivering and caring for a child could have been missed. And yet the cry one hears most often from new mothers begins: "Nobody tells you... " Every time a woman goes into labour, it seems, she is in for a shock. "No one told me how much it would hurt," says Harriet.

Of course, everybody tells you all these things, again and again. But the drama of childbirth is so personal and so enormous that new parents feel they have discovered something original - they are convinced that no one has ever felt this way before.

It was the emotional drama of motherhood that left Emma feeling that she had been kept in the dark. "No one tells you how you're going to feel. You're shocked by the intensity of the feeling. Theories you have read and absorbed are washed away by the emotion. It takes you completely by surprise and you're just left trying to blame people for not telling you."

"I really had no idea that you could love anything so much," says Amanda. "Well, maybe someone did tell me, but I probably dismissed it as sentimental rubbish."

The intensity of the experience, combined with the raging hormones and sleep deprivation, and the terror of looking after something so small and helpless, leaves some new mothers in a state of anxiety that can feel like madness. This is something no one can explain to a parent expecting their first child. If people don 't tell you about their own anxieties, it is partly because they don't like to admit to that sort of fear.

"Nobody tells you about the anxiety," says Sheila. "I had no idea that I would have attacks of such out-of-control anxiety. I felt like I was on drugs. My maddest moments were when I was pregnant. I ate off plastic plates for a week because I was worried about the lead in porcelain.

"It would have helped if somebody had said something to my partner," she adds. "It was so extreme - I couldn 't explain any of it to him. Men need to be given a lot more warning. He wasn't unsympathetic, but he had no idea what was going on."

To some, it can still seem as though there is a conspiracy of silence around childbirth. "Nobody tells you how much damage it does to you," says Harriet, who was "completely freaked out" by the state of her vagina after a tear became infected. But she acknowledges that, even if she had known the truth, it would not have helped. "If you 're about to give birth, what's the point of making you even more afraid?"

The indignities of birth are often cited as examples of how nobody tells you the important things. "Nobody told me I would shit in front of my husband," says one mother, a year after the event. "I feel I've never restored my dignity." There are aspects of the physical discomfort in the days following the birth that are certainly underemphasised. "Nobody tells you you feel like you'll never be able to poo again," says another. "It took me a week to be able to do it and it felt like having another baby; it was really traumatic."

The conspiracy theory is apparently borne out after you've given birth, when other mothers suddenly seem anxious to confide the blood and guts of their experience. At that point, it's as though you have been admitted to a club, and are privy to its darkest secrets. "I didn 't even know there was a club until I joined it," says Francesca. "But women tell each other everything after they've been through it. If you haven't done it, you can't understand it."

So how does a health professional approach the question of how to tell expectant parents everything? "It's very difficult to make it real and as it's going to be for each individual," says Cathy Finlay, NCT antenatal teacher and assessor. "I'm not sure it's possible. Nobody can tell you what it's going to feel like. I encourage my groups to feel that they are already parents. Some people will still be unbelievably shocked. We try to talk about things positively but not shy away from the truth. When women ask me, 'Does it hurt?' I answer that some women say it is extremely painful and some women would not describe it as painful at all. People relish the opportunity to scare you, but horror stories are not helpful."

According to Jan Parker, co-author of Raising Happy Children, "The attitude 'They kept it from me' is more prevalent among people who are accustomed to having control over their lives. It's probably the first experience that they were unable to control or educate themselves through. There is too much emphasis on the physical rather than the emotional side of preparing for parenthood. There are great swaths of the population who have no contact with others who are doing the same thing. The new parent is left thinking, 'It must be me, I'm doing it all wrong.'"

Underlying the new parents' feeling of being excluded from a charmed circle is a lack of confidence in their ability to understand or fulfil the baby's needs. This, Parker believes, is the key bit of information that is not getting through. "There is not enough emphasis on the early weeks," she says. "Getting to know your baby is the important thing, understanding its gestures, its cries, how it moves. Helping parents connect with the child can have a profound impact on parental confidence. It makes an enormous difference."

While other parents are usually eager to tell you everything if you're about to have your first baby, there's only a certain amount you actually hear. Much we don't register until it is relevant to our situation; and, with parenting, a new burning issue seems to occupy our attention every week, obliterating all that went before. I used to be exasperated by mothers who told me they couldn't remember how often they fed their babies, or when they first started on solids. How could they forget?

It's hard to believe that anyone goes into labour without being told that they will never get another good night's sleep. Emma and her partner had been told they would lose plenty of sleep after the baby was born, but like many others, they had not imagined how bad it would get. "I never believed that the lack of sleep would affect me so badly," says Emma. "I always thought, 'I'm not a typical woman: I'll be able to handle that.'"

Of course, information fails to penetrate in both directions. What pregnant women don't reveal is that, deep down, they are convinced that they won't fall into the common traps of early motherhood, that they will cope admirably with the birth, exercise daily and discover a rather fine singing voice to lull their baby to sleep. While rooms full of books and crowds of new parents lecture them about how painful, sordid and fearful the whole experience will be, they just don't listen. Which is probably just as it should be.