My husband was reading an article about love. It posed a hypothetical question, and he read it out to me. “If you were in a sinking hot-air balloon with your spouse and your kids, and you had to throw someone out so that everyone else could survive, who would you throw out?”

(Actually, that’s not a great hypothetical. Think three parachutes left on a plane and four people, or some kind of zombie apocalypse scenario.)

“Of course I’d throw you out,” I said to my husband quickly.

It was perhaps a little too quick, so I added, “I mean, I’d jump out myself, naturally. But of course I’d save the kids over you. You’d save the kids over me, too, right? I’d want you to.”

From the look on his face I could see that I should have at least pretended to think it through.

Don't get me wrong. I love my husband, I really do. But what I feel for my kids is different. It goes beyond love. It's something so deep and primal that I don't ever have to question it. I just know that I would do anything, anything, anything at all for my child.

Self-sacrifice, when it involves your child, isn't noble. It's just natural.

Many years ago, I knew a woman who donated a kidney to her daughter. She found it strange that people were praising her for it, as if she was doing something generous. To her, there was no question that she would do it.

At the time I thought she was being unnecessarily humble. Now I totally get it. If my child needed a kidney and I was a compatible donor, I would be weeping tears of joy as they wheeled me into the operating theatre.

This primal instinct to protect our kids can make us do crazy things. It can make us helicopter parents, constantly having to fight the urge to wrap our kids in cotton wool. People may scoff, but it's not like we choose that style of parenting. We can't help it.

WATCH a video showing a baby who really loves his mum. Post continues after video...

Not many of us will ever be in a position where we have to sacrifice our life - or our spouse's life - to save our child. But we make tiny sacrifices every day, without even thinking about it. You take off your jumper to give it to your shivering child. You cling to the edge of your own bed so your child can sprawl out comfortably in the middle. You hold the umbrella over your child's head and let yourself get rained on. You carry your child on long walks, no matter how much your own feet are aching.

It's one of the things that shocks you when you become a parent. You think you've felt love before - your sister, your husband, your dog - and then your child comes along. The ferocity of that feeling is terrifying. It makes you so vulnerable.

I'll say it again: I love my husband. In fact, I love him even more now than I did before we had kids. But maybe it would be safest if we avoided hot-air balloon rides.

Would you sacrifice your partner for your kids?