There is no denying that these days we are leaving it much later to start a family than our mothers and grandmothers before us did. When I got pregnant on my little girl, I remember feeling like I was going to be a really young, cool mum – which, in my own humble opinion, I was, of course, but at the same time, I was also, at 28, a full five years older than my own mum was when she had me. In Ireland, the average age of first-time mothers have steadily crept upwards over the last decade, and now stands at around 31, making Irish women – on average – the oldest first-time mums in Europe. This obviously comes down to a lot of reasons, like education and cost of living and generally wanting to establish a career and possibly even buy a home before deciding to start a family. But it also means that infertility and treatment for it is on the rise. Because despite women today hanging on to their youthful looks longer, on the inside, our eggs still age at a chronological rate. Meaning, no matter how long you have spent at the gym and how how many juice cleanses you have done, if you are 35, then so are your eggs. What is also on the rise is secondary infertility – meaning that while you might have gotten pregnant and had a baby no problem the first time around, but when you start trying for #2, it just isn't happening. This is also related to age, of course. As in, the older you are having your first baby, the older again you will be when you are ready to go again. Which is why a bit of forward planning might be the way to go, guys. And now you can. A new computer have just crunched over 300 years worth of fertility data to come up with the age by which couples should start building a 1, 2 or 3-child family – with either a 50, 75 or 90% chance of success, and takes into account conceiving naturally or with IVF. What it found? Well, according to the chart, if you want jsut one baby, then you'd need to start a family at the age of 32 to have a 90% chance of conceiving (without IVF). But – and this might give some people a bit of a fright – if you want three babies then it says the best time to start trying is at the age of 23 to have the same chance of success! The computer model assumes that couples “start trying for the next pregnancy on average 15 months after the birth of a child”, so couples need to factor this in too. This is what Dik Habbema at Erasmus University in Rotterdam, one of the creators of the model, had to say:

"We have tried to fill a missing link in the decision-making process. My son is 35 and many of his friends have a problem deciding when to have children because there are so many things they want to do."

Allan Pacey, professor of Andrology at the University of Sheffield in the UK explains further:

"What it is saying is that if you’re relaxed about having three children, you can wait until you’re 35, but you’ve got to start early to be certain."

Pacey thinks charts like these are important and that a conversation about fertility and family planning needs to happen.

"The table ought to be photocopied and put up on the clinic wall. We should also be aiming this at sixth formers and university students, so that they’re aware of how to plan their life. We haven’t got a time machine we can put people in … that’s just a blunt reality. Everyone thinks they can wait – this shows that you can’t."