If you were to spend time in a maternity ward listening to proud new parents, you’d definitely hear them discussing their offspring’s genetic heritage. Does the new baby have her eyes or his? Could that be great Uncle Charlie’s nose? What you won’t often witness is the father turning tenderly to the mother and murmuring, “Hey, he looks just like Phil! You know, your ex? With the motorbike, and sociopathic tendencies?” But new research suggests that this scenario is more plausible than it sounds.

It has been shown that newborns may resemble a mother’s previous sexual partner, after scientists at the University of South Wales observed an instance of telegony – physical traits of previous sexual partners being passed down to future children.

The researchers found that, for fruit flies, the size of the offspring matched the size of the first male the mother mated with – not its biological father. It is thought that molecules of the semen produced by the first partner might be absorbed by the mother’s immature eggs.

“We don’t know yet whether this applies to other species,” explains author of the study, Dr Angela Crean. Too late, Dr Crean! I’m already working my way through a mental Powerpoint presentation of my exes and trying to work out whether I can travel back in time with a box of Durex.

The idea of our unborn children resembling partners past might initially fill us with horror, no matter how amicably your relationship ended. Your ex is not supposed to lurk inside you, waiting to burst forth in miniature form. This idea is scarier than Alien.

I’m sure plenty of prospective mothers feel incredibly guilty about the fact that they might be, unwittingly, about to fill the world with children who blow their nose on their sleeves, claim they have a moral objection to booking restaurants, and pronounce the eighth letter of the alphabet “haitch”.

However, if the hypothesis holds, it might not be entirely bad news. Whether we like it or not, the people we choose to date, and sleep with, reflect something of ourselves. It’s easy to write off past relationships in the same way we shudder at old pictures in which you’re wearing embellished, stonewashed denim. “Past me was such an idiot!” I often think. “I’m much wiser now.” But we ought to give our old selves more credit for doing what seemed right at the time – or at least acknowledge the fact that every decision which feels right now could seem just as foolish in five years.

If your children do share some traits with your former partners, it probably only shows the way that you were previously nurtured affects their nature. You’re human, and just as you’ll face difficult choices and make mistakes after they’re born, the way you behaved before they were born could impact on them too. Essentially, you have to accept that your old partners had admirable qualities which drew you to them in the first place, and that you’d be happy to pass them on to a child - or you have to admit that your current partner might also have bad qualities, and you’d be better off if you didn’t have children with anyone.

Despite the fact there’s still no solid evidence that the study applies to human reproduction, small children and exes can be equally irritating. You might, sleep deprived and frazzled, look at the freshly bathed toddler who has just started to massage their scalp with spaghetti hoops and think, “My ex used to make me feel this weepy and panicky! This must be his baby!” – when they don’t really have anything in common, just that your former partner used to act like a big baby and your infant child actually is one.

Ultimately, it’s down to you to teach your child to be a responsible citizen and happy human being. You may not have had the power to change your ex’s worst habits, but if the theory of telegony is true, you can find some satisfaction in taking control of the way their descendants behave.