Tell me you don't know this woman: She started seeing a guy when she was aged 28 or 32 and the dude said he wanted to get married and have kids, but the time wasn't right.

They had some fun, moved in together, but he had issues in his 30s (don't we all) and she was right there beside him, waiting for him to turn the corner.

And he did. Except, when he got there, he decided the relationship "wasn't working" and the woman found herself single again at age 35 or 38 and is now staring at the very real possibility she'll never have children.

I call these guys vampires because they just suck the life out of women.

Now, before my more militant brothers call me a feminist-apologist mangina for the 912th time, I'm not suggesting there's not men in relationships where women also suck the life out them.

It's just that the whole baby/fertility/eggs thing really makes it an uneven playing field. Guys can have the life sucked out of them, be lied to and led on for a decade, yet they can still pop out a sprog at 45, no worries.

Women? It's tough. Not impossible, but it's waaaaay more difficult than when you're say, 25 or 30. I'm also not suggesting a woman in her late 30s is any less attractive than a woman in her mid 20s (well, not in print), but the dating scene doesn't get any easier as you get wrinklier (I should know).

Vampires are real, but in this city they take the form of men who'll bleed the youth out of a woman, then cast her off. I know these guys. I've drunk with them. They're deadly.

If you accept the somewhat unromantic, determinist idea that we're actually only here to reproduce our DNA, these guys are literally the death of your bloodline.

They're the human equivalent of the morning after pill because, while you're with them, you're actually ensuring you will never become a parent and experience what is quite possibly the greatest thing that can happen to you - staring into your child's eyes.

This is how it breaks down. You meet this guy when you're 27, you think it's on forever and ever, amen. Maybe, early in the piece, he thinks the same way but at some point you become his backstop, his insurance policy and if someone "better" comes along he is goooone.

You could argue the guy just didn't want kids blah, blah, except these dudes always seem to impregnate the next (much younger) woman they date, about year after dumping their long-suffering, long-term girlfriend.

I know a guy who did this to a friend of mine and he better hope I'm not the one driving past if he's ever trapped in a house fire. I'll buy marshmallows to toast.

Perhaps this is why so many middle-aged women are into Twilight and True Blood? Vampires idealise their real life relationship, or a past relationship they're still trying to rationalise?

You might think I'm being flippant, but I'm not. It's a disgraceful thing to manipulate a woman in this fashion. In many cultures it can get you killed, which is a reflection of how seriously messed up it is to deprive someone of the right to procreate.

The good news is, like vampires, these guys are easy to spot, you just gotta drag 'em out into the metaphorical daylight, which sounds something like this.

"Hey, I'm going off the pill."

If he bares his teeth, you know what you're dealing with.

Sam de Brito's latest novel Hello Darkness is in bookstores now. You can follow him on Twitter here. His email address is here.