39. The atomic number of yttrium. Part of the title of John Buchan’s famous novel, The Thirty-Nine Steps. The international direct dialing code for Italy. The sum of five consecutive prime numbers (3+5+7+11+13). The duration in nanoseconds of the reaction in the largest nuclear explosion ever conducted.

It’s also the number of weeks pregnant that Heather is today. In other words, she’s due in exactly one week’s time.

This is the third time around the block for us: Isaac (aged four) was born in December 2007, while Toby (aged two) arrived in January 2010. It’s a running joke in our household that Heather only works in odd-numbered years. (Personally, I think she does it so that her maternity leave always coincides with the major summer football tournaments in even-numbered years.)

Each nine-month period has been distinctly different. The first time, of course, was novel, exciting and a little bit terrifying. Religious reading of and adherence to the appropriate baby books. NCT classes (we’re so middle-class). Ticking off everything on the to-do list at least a month in advance. Bags packed? Check. Names shortlisted? Check. Crib, newborn clothes and other baby paraphernalia so numerous that you need a removals truck to accommodate it all? Check. Champagne in the fridge? Check. Twiddling our thumbs while we waited 12 days past the due date for Isaac to arrive? That wasn’t in the plan. So we went out to eat. A lot.

Second time around, things were much more relaxed. The names were chosen, the bags were packed and all the relevant stuff was retrieved from the loft a couple of weeks in advance. Heather skimmed through the baby books again as a reminder, and asked me to do the same. I eventually got round to that when she was two days overdue, and was literally curling up in bed to brush up on the birthing process when she went into second stage labour. I had just enough time to phone our midwife – as with Isaac, we had been planning a home birth anyway – and get Heather downstairs before all hell broke loose and I realised that this was going to be a DIY delivery.

You can read the full gruesome story – it’s post-watershed stuff (not really) – elsewhere, but suffice to say everything worked out fine. Earlier that evening I had watched an episode of the American TV drama Brothers & Sisters which – instructively – featured a birth scene. Only there a group of actors in matching, pristine surgical gowns glided purposefully around a delivery room in beautifully choreographed slow motion to the strains of Coldplay’s Fix You, while the father-to-be collapsed in a car park with a non-fatal heart attack. What more do you need to know about childbirth? In the event all I had to do was catch Toby as he slithered out, check for breathing, wrap him in a towel and try not to pass out until the midwife arrived to do all the complicated stuff. Simples.

Toby and Isaac - brothers in arms

This time I have to admit I’ve been positively relaxed about the whole affair, almost to the point of being blasé. It’s not that I’m not really looking forward to the new arrival – I am – but there’s definitely an element of  ‘seen that, done that, got the t-shirt’ about it. We’ve done everything we need to do – the bare minimum, admittedly, but we’re ready – with more of a just-in-time mentality. Baby names were decided over a relaxed dinner out (one of our traditions) last week. The boys have been fully briefed – Zac is very excited, Toby fairly nonplussed other than being very clingy to his mum. I’ve warned everyone at work to be ready for a sudden phone call and a dramatic dash to the car – in my mind’s eye, I will be doing it to the theme tune of The Six Million Dollar Man. And, er, that’s about it. I’m sure there are a few small things we probably should have done by now, but nothing major. We’re good to go.

It’s just a matter of when now. Life – as the saying goes – begins at 40 (years, that is).  But I rather suspect this baby is going to arrive before the weekly counter ticks over to the big four-oh. If things go quiet on this end of the blog, you can probably guess where I am. I won’t be playing Fix You, though.