In theory, it’s easy: you’re a runner; you become pregnant. Research shows that exercise is beneficial throughout all of pregnancy; it’s good for mums and good for babies, ergo, you keep up the running and nothing has to change.

The practice doesn’t feel so straightforward. The mental shift from regular to pregnant running feels something like the difference between saving for a holiday and saving for a pension.

Pregnant running isn’t just physically tougher going than usual (though certainly the physical changes don’t help) – it’s psychologically entirely different to running ‘solo’.

When I run – normally – it’s something I do just for me. On one level, it’s an indulgence; it’s a way of finding a quiet space; it’s pure escapism. There’s no pressure at all to be responsible for anything or anyone else. On another level, it’s an outlet for my competitive nature: every run is a succession of challenges; can I make the next mile faster than the last one? can I run the same route faster than last time? can I go a bit further than I told myself I would? and can I go a bit further again; fit in one more hill or one more sprint than I thought I’d settle for?

Four months in: combatting nausea with bright tights

Pregnant, that doesn’t work so well. For a start, after a certain point it’s fairly inevitable that the next run will not be faster than the last one; it will be slower. I will not feel lighter, better, fitter and more energised the more I train: I will feel heavier, more weary and less able to make it through the day. So the usual training rewards are not there. Can I ignore all that and keep going anyway? Well, yes, to a point; but is it really sensible to do that? Is it responsible?

Six months in: bigger and slower!

As a pregnant woman, I’m acutely conscious of my body as a shared space. It’s not entirely my own – it doesn’t really look like my body, and it certainly doesn’t feel the same as normal – and I feel compelled to use it considerately. That’s not an adjustment that comes naturally – nor terribly easily – and adapting to accommodate it takes the heart out of my training.

For me, half the fun of running – or cycling, or spinning, or circuit training – is in keeping going when it would be easier to stop, and finding out just how far I can keep going before I absolutely have to admit defeat. As a qualified pre- and post-natal fitness instructor, I know very well that this is not a healthy nor suitable approach to exercise for a pregnant woman; it’s exactly the kind of attitude that I would discourage, in fact – but without it, training isn’t that much of a pleasure for me any more. It’s more like a chore.

Pregnant running, then, feels the same as saving for a pension. There’s every good reason to do it – but there’s little short-term gratification and it doesn’t really feel like fun. There’s clearly a long-term payback: the likelihood of a faster, easier labour; a healthier, leaner baby; a faster postpartum recovery and return to pre-pregnancy form; it’s all an investment in the future. But I have to admit, I’ve always been better at saving for holidays.

Seven months in: final run

Right now, I’m 32 weeks’ pregnant – all being well, that means I have eight more to go. The first time round, I kept on running up to 32 weeks. I’ve had a niggling feeling ever since that I could or should have somehow managed to do more, so this time I was secretly determined to carry on for at least as long. It wasn’t to be: it’s true when they say that every pregnancy is different, and I ran my last 5k of this pregnancy two weeks ago before admitting defeat and mothballing my running shoes until after the new arrival. For the next few weeks, the bump and I will be swimming – I’m a terrible swimmer, but it’s better than doing nothing, and more to the point, I’ve found myself a new goal to get excited about: the Vigour Events Pilmuir Aquathlon is in my diary for June. With a following wind and a bit of swim training in the bag, I reckon that by that time I might be about ready for my first open-water adventure as a sleep-challenged mother of two …