Every woman’s journey to motherhood is unique, but like Susan Green, the heroine in my novel “The Cactus,” mine came later in life and with its own set of surprises.

As I do with most things, I dithered about the right time to become a mother. I was thirty-eight years old when I had my first son and forty-one when I had my second. By the time I’d crossed the mid-thirties line, friends, family and colleagues were starting to think I must be having trouble conceiving. After all, my husband and I had been together for over ten years. But we both regularly worked late, and I had a lengthy daily commute from one city to another.

We’d honed our weekday routines with precision so that our lives ran smoothly and predictably. When we weren’t working, we spent time hiking in the mountains or enjoyed weekends staying with friends (often involving a fair amount of wine). We knew we wanted children, but where on earth would they fit into the equation?

In “The Cactus”, Susan is forty-five years old when she finds out she’s pregnant—a pregnancy she neither planned nor wanted. She is a woman who likes to be in control of every aspect of her life. She can’t abide unpredictability or spontaneity, and therefore avoids personal relationships and emotional entanglements. As a result of her childhood experiences, she’s evolved to survive in an emotionally arid environment. With more in common with her beloved cacti than she realises, her mantra is, “If you never let people get close to you, you can never be hurt.” I was interested in exploring how a woman such as Susan would cope with the tsunami of changes, both physical and emotional, that I knew she would experience as a result of pregnancy and the other life events bombarding her.

Over the course of the book, Susan is surprised by the myriad ways that pregnancy transforms her—most notably in her interactions with others. Though the circumstances of my own life were quite different, I, like Susan, found that by the time I reached my late thirties, my long hours working and commuting meant that I’d let female friendships drift. I’d begun to feel slightly isolated, and, as many women do, found myself in a bit of a “couple bubble.” When I became pregnant, my body began to do strange and wonderful things, and my emotions were all over the place. I was excited about the new life to come but terrified about how I would cope.

In confusion, I joined birth preparation classes and groups for expectant and new mums, where I made great friends with women from a variety of different backgrounds. Something similar happens to Susan in “The Cactus” as she finally allows people into her closely guarded world. Could it be that, for the first time, she might actually have a close emotional relationship and a proper friend?

Motherhood is a life-changing journey at any age, one that comes with unexpected joys, sorrows and lessons.

Once you have children, it’s no longer possible to live an emotionally isolated existence. Neither is it possible to have complete control over your daily life. Who wants that, anyway? It’s those unplanned and unexpected events that can bring the most happiness. And, for me, entering a whole new world of female friendship and support has been one of the many surprising and delightful consequences of the journey to motherhood.