Confessions you’re unlikely to overhear at the school gates: “I want to put my kids up for adoption and get my old life back.” Or how about this: “I fantasised about killing my babies.” Or: “Suicide is always on my mind. If I kill myself now, my child won’t remember me.”

The author and new dad Michael Lewis admitted in his latest book, Home Game: An Accidental Guide to Fatherhood, how boring and disappointing he found fatherhood. His experience had him “drowning in self-pity” and wondering what he’d do “if it wasn’t against the law to hurl [my baby daughter] off [the balcony]”. Mothers, he argued, just don’t have the same problem, because they are blessed with a maternal instinct. However, behind the veil of online anonymity, protected from judgment and finger-pointing, more and more mothers are also admitting as much — the confessions above were found on parenting support forums such as Mumsnet, Netmums and Parentline Plus. In fact, 75% of callers to Parentline Plus’s free support line — for “the call you make at 2am instead of reaching for the bottle or the axe” — are mothers, and only 11% are dads (the rest comprises steps, grands and so on).

As one miserable mother confides on Mumsnet: “There is so much pain, so much frustration and so little joy [in motherhood]. From the outside I have a great life, yet I feel trapped in a gilded cage. I have never even come close to telling anyone how I really feel, which is, I feel, the crux of the problem.” Another says: “The conspiracy should be blown apart because the result is a lot of women feeling inadequate and a lot of [children] confused as to why their mummies are so unhappy.”

Out later this year is The Mother’s Tale, by Camilla Noli, a fictionalised version of Noli’s own experience of raising two young children, who — in the novel, not real life — the narrator murders.

“I was writing from my own experiences and fears, saying what other mothers won’t,” says Noli. “If the bond is missing, and you’re stressed, then the stage is set for potential tragedy. Many mothers have shared with me that they have found themselves at the point that the narrator reached.”

While in real life the suffering mostly goes on in silence, there is, at least on forums, someone taking notice. “We’ve sent a few ambulances round after noticing suicidal posts on Mumsnet,” says its co-founder Justine Roberts. “Our ‘Feeling Depressed’ boards are full of people for whom motherhood is not living up to the dream. Very often, people just need to know someone is there to listen to them. Websites like ours stand in as community support.”

Blame our atomised society, blame the fact that our families are increasingly fragmented across the country, blame our stiff upper lip... Or could this all be put down to postnatal depression (PND) or postpartum psychosis? To a degree.

According to Parentline Plus, the biggest reason for calls to their helpline is parents’ mental health — largely, they say, issues of anxiety and stress. While up to 22% of all new mothers suffer from some form of PND (according to the Counselling Directory), many believe a lot of the blame lies elsewhere. They ascribe their maternal ambivalence to having been duped by unrealistic celebrity role models who peddle the myth that nothing changes post-motherhood, and that good looks equals happy lives. “I feel I was sold a lie,” writes one.

“This is the fallout of the have-it-all generation,” says Roberts. “Mothers are under so much pressure to have it all and do it all right. Plus, they’re expected to look slim and fashionable. Nobody is allowed to be just good enough. It’s almost impossible to achieve, so when they don’t, they feel rubbish.” And, of course, there is the perennial stay-at-home/working-mother debate — the mother who goes out to work feels huge guilt leaving her sick child, say, or placing them in the care of strangers; the stay-at-home mum loses her sense of purpose and connection.

The rise of the mature mother is also a factor. “Younger mothers are generally more laid-back,” says the fertility expert Zita West, who has opened a postnatal visiting service at her London clinic, to help new mothers struggling to adjust. “Older mothers build up their expectations. Plus, because they know a lot more, they’re more anxious.” And, of course, that mummy tummy can be harder to shift. For those who have “left it late” and have two children in short succession without recovering from the first, it can be a much bigger deal, says West.

Perhaps it is the high-achieving career woman who is most vulnerable, after suddenly finding herself demoted to the bottom of the pile, enslaved to a baby, and with the thought of returning to work hanging over her like a sword. West, a self-confessed overachiever who has a daughter and a son, now 24 and 21, relates to this. “It was the lack of being able to achieve anything in the day, not even having a shower,” she says. “There’s huge competitiveness in parenting. I stopped visiting friends because I was a mess and they weren’t.” West sees many high-flyers who work right up until the moment they deliver. “They go in tired, so they come out tired — their reserves are exhausted.”

But wait — cancel that hysterectomy. Motherhood isn’t always a secret hell. Many women make the transition very well, says West — those that have a good support system, of parents, sisters, friends. Plus, there are phases to watch out for — like at four months: “You feel so special at first,” she says, “but when the post-birth attention has faded, it’s a very different reality.” Not having too many expectations of yourself is also key. “I’ve encouraged women to stay in their pyjamas for as long as possible,” she adds (because otherwise, you have a much clearer point of comparison to your former self). Noli herself says hers was a positive experience, though difficult at times. “If we pretend motherhood is easy, we set mothers up to fail.”

The fact is, it’s only when we are honest about our problems that we can be helped. It’s good to talk — just maybe not at the school gates.