I'm on the bus to Shawlands with my two-year-old. We’ve crammed through the hordes and I parked his buggy by the window seat. I stand behind him to steady it, since he is a giant 98th percentile of a toddler and his buggy looks like it's made from tissue paper and matchsticks when he’s in it. A kindly woman looks at me speculatively. I know what’s coming. She looks away, looks back again and finally leans forward to say quietly, "Do you want to sit down?", nodding towards my rounded belly.

At this point, I could tell her that I’m not pregnant. I'm just a 42-year-old on the chubby side,  wearing an empire line dress, taking handfuls of steroids for chronic illness and coincidentally can't, indeed never would, refuse an Empire biscuit. She means well though, so instead, I smile at her nicely: "No, no, thank you. I'm fine. I need to hold onto the buggy."

Thankfully, I'm not often mistaken for being pregnant but the silent question of whether or not I want to have a second child, or sometimes the very audible question of whether I will have a second child, is often in the air. When I started my work at the University of Glasgow a colleague very kindly told me about their excellent maternity policy before they told me any other HR information. At literary events, while teaching, when meeting acquaintances or relatives, That Question always comes up. "I suppose it’s time for a second one now?"

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They think this because my son turned two and this seems to be the age that many parents have taken their second jump off the parenthood cliff. Far enough from the newborn years to feel human again and soon enough that there won’t be a huge age difference. I try to be diplomatic when answering."Oh no. I think one is enough for us. We already did it perfectly" I laugh, but in reality what I'm thinking is: "Are you kidding me? I've only just started looking like I didn't create his life by draining my own soul."

In truth, we always thought we would be a one-child family. There were practical reasons for this, I didn't meet my partner until I was in my mid-thirties and we waited until the relationship was solid as a rock before we even thought about having a child. I was also establishing my second career as a writer at the time and didn't want to hit the glass ceiling, or the "sticky floor" as some people call the ramifications of having a child and then getting "stuck" when you’re a woman. At the time we were also living, and renting, in London, one of the world's most expensive cities. We couldn't imagine how we would find the resources to have our child and as someone who grew up in extreme poverty, it was an absolute non-negotiable that my child would have, at the very least, everything they needed.

Besides this, there were ethical concerns about the climate crisis and overpopulation. The fact that if we were to have a second child it would be very hard for me to justify not adopting or fostering especially as I had been a care-experienced child myself, and I honestly didn’t know if I had the emotional mettle for that.

Some of my friends were horrified by our choices: "Aren’t you worried your child will be lonely?". And it’s true the term "only lonely child" does occasionally echo through my mind. But perhaps because neither me nor my husband had traditional relationships with our siblings, his being much older and mine being much younger, we know that that sibling bond is not essential or even guaranteed. Ultimately, our child is anything but lonely. He is the friendliest, most extroverted kid. He is also, and may this statement not blow up in my face and singe my eyebrows, an overwhelmingly "good" boy. Though I’d like to take credit I think he is just a sweet, easygoing kid but perhaps it has helped that he’s never had to compete for our time or attention or adjust to any new family addition unless you count our rescue dog.

Are we spoiling him? I don't really believe in spoiling a child but I am watchful that my efforts to make him feel that his life is not straitened like mine was don’t go overboard. My husband grew up wealthy with everything he wished for including choosing a new toy from Hamleys every single week. I grew up improvising with making a deck of cards and a saucepan lid for my toys. Neither of those extremes feel right to us so we try to bring our little boy up in the middle of our experiences.

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It seems that we’re not alone in having one child. Recent research has shown that in Europe 49% of families have only one child. In the UK this rising trend is said to be because many women are choosing to have children later in life just as we did, and for many of the same economic and practical reasons.

Besides this, recent data from the Faculty of Education and Society at University of College London shows that in fact, only children in the UK are are "doing just fine" stating that "only children have similar scores to children from two-child families and higher scores than children growing up with two or more siblings." They call this the "only child advantage’’.

When I explain that we are "one and done" it is still sometimes difficult to shrug off the look of sympathy, disappointment and occasional judgment in the other person’s eyes. But I smile and use a line I’ve found helpful for all manner of assumptions, intrusions and unsolicited advice. I simply say: "We find this works best for our family.’

Ultimately, I think that whatever size family you choose is best for you. I guess the proof is in the pudding. But so far, we are a small, often chaotic, but deeply happy family and it doesn't feel like we're missing out even a single bit.