Last weekend I met a woman at a party. I never did catch her name but during some 20 minutes of conversation, I learnt all about her breasts (engorged), the emotional disconnection she feels at work (acute) and the state of her sex life (very poor).
To the uninitiated this might sound like an alarming deviation from the usual boundaries of sober Sunday afternoon chit-chat – how much you have to learn. Over-sharing between previously unacquainted mothers is a national pastime for roughly four-fifths of the female population in Britain. There is something about having a baby that crosses social boundaries like nothing else.
New research shows that before becoming a mother the average woman has a circle of 13 friends. In the year after birth this increases to 22 and by another five once the child starts going to school. Of a sample of 2,000 mothers interviewed by the baby-care business Nature's Purest, half said they found it easier to bond with other women once they became parents, while four in 10 said they felt comfortable sharing intimate and personal information with new mothers they had only recently met.
Sue Firth, a psychologist who has two children, is unsurprised: "There is a strange shift. At no other time in your life do you unzip your guts and just start talking in quite the same way." She believes it comes down to the fact that there is "no prescription or template to follow about what being a mother is really about". As a result, this is one of the few times in your life when "it is OK to say you don't know, to admit to your vulnerabilities".
Charlotte Thompson, who has three children, was one of the people consulted in the study. An occupational therapist's assistant from Yatton, Bristol, she sought out new friends since having children because, she says, "my existing friends became slightly distant as I couldn't really discuss how exhausting it was to be up at 4am with friends who didn't have kids and had no idea how I was feeling. They wouldn't understand and wouldn't be interested either".
It was a mere few weeks into my own pregnancy that I got the sense that my friendship circle might need to broaden. I was 27 – the national average age for a first-time mother but still the youngest of my friends by far – and the precise moment of the epiphany was when I confided to my best friend that I was expecting a bouncing babe and she replied: "Oh, shit, what are you going to do?"
So, like many expectant mothers, I shuffled along to antenatal classes not because I was compelled to learn about breastfeeding (something which at that point I foolishly imagined involved a non-negotiable point-and-suck technique) but because I wanted to make new – supplementary rather than replacement – friends. I certainly didn't want to be one of those people who sit around in cafés for hours talking about haemorrhoids and paper knickers, but I did have an irrepressible yearning for someone who would just… understand.
While two years later, my "real-life" chums – as in the ones I had pre-baby – have proved endlessly supportive and invaluable, not least for those moments when you want to go out and forget all about potties, tantrums and Peppa Pig – I couldn't have got through it without a handful of fellow mums who, frankly, I would never have come across, let alone become close friends with, in other circumstances, given one of them is 10 years older than me and another is teetotal.
There have been dark times, too, particularly when my maternity leave was up and suddenly conflicting work schedules and children's sleeping patterns meant an increasing number of afternoons pushing swings alone in the park – something once described to me by another mother as "the loneliest feeling in the world".
While motherhood offers opportunities for new lifelong bonds, it can also be a time of crippling solitude, not least given that post-baby blues affects more than half of new mothers. In the past, research has found that two-thirds of mothers were left feeling "lonely and isolated". Modern living, where people no longer live in close-knit communities, the survey by Mother & Baby magazine claimed, was making motherhood more of a challenge with women removed from their traditional support network of friends and relatives.
Jenny Scott was 28 when she became pregnant with her son: "I was totally naïve. I thought 'my life is not going to change, I won't need new friends'. I was in for the biggest shock."
Once her son was born, Scott, now 31, says: "I was so lonely I used to go on walks to the park, chatting up women in buses or at the doctors and try to make friends. I hadn't realised I would be on my own all day."
Rather than continuing to stalk local parents, she launched Mothers Meeting, a meeting point for "creative mums who don't want to lose themselves just because they are parents", and started arranging get-togethers.
In the early months, she says, it was primarily about finding someone with whom to share the culture shock: "When I first become a mum I was so traumatised by the birth experience I wanted to speak to anyone and say: 'Wasn't that the most mental thing ever?'"
But soon those friendships began to serve a wider purpose: "After couple of months you get over that, bored of talking about breastfeeding and that stuff, but you still want someone you have something in common with, but not just [a] baby." While "kids don't have to take up every kind of conversation", she says having that common experience brings an unspoken bond. One of the things I hadn't anticipated about maternal friendships was how complex they can be. I'd thought having a kid was having a kid. No, no, no. While it might be a great ice-breaker, being a mother isn't necessarily enough to sustain a friendship long-term if other commonalities aren't there. The age of the baby is an all- important factor. In the first year, a matter of weeks can set a new mum far apart from her peers, though this divide decreases in time.
But there are all manner of complicated factors that parents use to ally themselves with and against each other. "The biggies," as Firth calls them, being breastfeeding – "your choice in this matter can polarise you one way or another".
The second, she says, is whether you work or not, "which can cause quite strong divides". Though as she points out, people always need to find some way to ally themselves with or against each other.
Unsurprisingly as time has progressed, the natural filters have sifted casual acquaintances from those who have gone on to become proper lifelong friends.
Of all the women I've met on the muddled path through the first few years of motherhood, there are a handful who have passed the test of time. There is something about seeing your own friendships reflected back at you in those of your respective children as the bond between them grows, that is – for want of a less soppy sentiment – life-affirming.