They say good – and bad - things come in threes. It’s a magic number after all. Buses, lions, wishes - they all come in threes, writes Ellen Widdup.

Not to mention little pigs, blind mice and porridge eating bears.

Then there are Stoodges, Bee Gees and Amigos.

And what about the third dimension? The Holy Trinity? The fact that Earth is the third planet from the Sun?

All the best jokes have an element of three. The Englishman, the Irishman, the Scotsman.

Then there are famous speeches and the power of persuasion. Think liberté, égalité, fraternité.

Even in writing, there is the rule of three. A principle that three-part lists are inherently funnier, more satisfying, or more effective.

It’s a pleasing number on the whole. One that denotes luck – unless you have had two lots of bad luck, in which case you are set for a third.

This year my husband and I have had two out of three good things happen.

We moved house and we set up our own business.

Quite monumental things. Sensational things.

You might say we’ve had our fair share for quite sometime. That’s enough excitement. There’s no point being greedy.

But here’s the thing about the rule of three: it’s out of our hands.

At least, that’s what I told my husband when, on Mother’s Day, a thin blue line appeared that cemented our third life-changing bit of news for 2015.

“Pregnant?” he asked incredulously.

I’m not sure why he was so shocked. This is one area where two is more effective than one (and can equal three).So yes. Dah dah! Numero trois is on the way and due to make an appearance sometime in November.

Well, we all knew it was on the cards didn’t we?

In fact, ever since I wrote that column six months ago expressing my desire for another baby, I was asked repeatedly whether I had a bun in the oven.

Now they don’t need to ask. So much for bun. I look like I’ve swallowed a black forest gateau.

Here’s the thing about pregnancies. You get fatter, quicker, with each one.

You also get sicker.

You would think that if I am to puke my guts up from 8am until 8pm every day, I should at least be able to intersperse each bout of vomitus by shoving pastries in my mouth and not worry about gaining a single pound. But somehow, in the 10 minutes the food stays put, the damage is done.

There are other distinctly different things about carrying a third child.

When you have your first, you become the centre of the universe.

No-one has ever had a baby before; this is the most important event in the history of the world.

You rest, you plan, you glow. You walk around like an earth mother, hand on your belly, relishing your neat bump. You feel calm and smile a lot.

You even love the nausea because it connects you to the baby inside.

You eat fresh organic produce. You do a little light yoga. You are overwhelmed with information and advice.

You have a baby shower. People are excited for you.

When you have your second child, you look like you are six months pregnant by the time you hit the second trimester. You feel harassed and yell a lot.

When you are not yelling, you are crying. You are tired. Bone-achingly tired. But you have another child to care for so you can’t nap.

You love the nausea and vomiting simply because it means you get five minutes to yourself in the bathroom.

You eat your toddler’s leftovers.

You are irritated with advice.

You don’t get a party.

Three months into pregnancy number three and you are huge. Colossal.

You also look like a cast member of the Walking Dead. Your hair is greasy one day, and splitting, dry and coarse the next. You have spots.

You spend a vast proportion of the day gagging, throwing up or holding your nose. You eat whenever you are not being sick. You get chronic flatulence. And blame the baby. Or the dog.

No one bothers offering you advice.

People either think you are crazy or irresponsible. They laugh hysterically when you tell them it was planned.

Your husband has no sympathy. You were the one who wanted another. Your children have little patience for you either.

They prod your tummy, invent stupid names for their sibling. Fight over who it will love best.

All this is ok though. I’m not complaining actually.

Yes, perhaps I am mad. Two’s company, they say. Three is a crowd.

But I think secretly a lot of mums out there with two, yearn for another.

Do an internet search for “Should we have a third child?” and you’ll unearth a minefield of deep maternal angst.

Some think it is an indulgence. Others feel two children is the social norm. Yet more worry that third children are the equivalent of a third wheel: unnecessary, unwieldy, and surplus to requirements.

A few worry that three would be some kind of interminable endurance test with TV comedies such as BBC1’s Outnumbered doing little to help challenge that perspective.

But such myths should never be the grounds on which we base life’s big decisions, should they?

No. Neither should superstitions about the number three really.

Having said that, it’s happening.

So I think it makes sense to take the attitude of another famous trio: “All for one and one for all!”

Tweet Ellen with your words of advice @EllenWiddup or see more from her here