The secret agony of every parent.

M is ill at the moment.  Not, I hope, really ill, but ill enough that the words "maybe we'll admit him if" have been mentioned.

While I sat in the surgery for the second time in 24 hours, M floppy and listless against me, I realised that when you're pregnant everyone wants to share their stories with you.  They tell you about stretchmarks and piles, forceps and stitches, epidurals that don't work and midwives that don't care, sleepless nights, colic and exploding nappies, stomach upsets, fighting and whinging.

They tell you about the night, six weeks in, that their husband said: I can't take this any more, and walked out, letting the door slam behind him.

Or the New Year's Eve in Edinburgh when their two week old twins screamed and screamed, until babies and parents fell into an exhausted, fretful sleep at 11.45p.m.   A sleep which lasted only fifteen minutes before the whole world exploded in a crash of light and noise and heaving I can't cope sobs.

Or the time they fell asleep on the sofa, cuddling their three day old baby.  And the baby rolled off them onto the floor, and they woke to the scream, and the wide open eyes of accusation and pain.

And all those things are (and were) awful.  Frightening and painful and tough.

But none of them is the worst thing about parenting.

This is the worst thing about parenting.  Everyone must know it, but no-one talks about it:

You can't keep them safe.

They are the most perfect human beings ever to have existed and you'll never be able to keep them safe.

When L was about four days old I rang my mother in tears.   I couldn't bear to put L down because I was frightened that she would never wake up.  But I was scared of more than that. I was scared of everything: grazed knees, tummy upsets,  broken limbs, broken hearts, muggings, assaults, injury, illness, death.

My baby will get hurt, and however hard I try I can't stop it, I said, through sobs.

That's what being a mother is,  my mother said.  I still feel like that about you.  Admittedly, I don't worry so much about you having a bath on your own, but I don't sleep well if you're out of the country and I start to panic if I ring you twice and I can't get hold of you.  It doesn't change because you're grown.  It's just there, and it never goes away.

I didn't know. How could I know? No one told me.

Every night before I go to bed I do the rounds of my children.  I go to A and S first.  Normally one of them has fallen out of bed, so I pick her up, and steal an extra cuddle.  I tuck her in, and then her sister.  I kiss them both, listening to the rush of their breathing.  I go to L, normally face down in her pillow, hair hiding what little of her should be visible.  I brush it away and kiss her too.  I move to M's room.  I can't reach to kiss his face over the bars of the cot, but I stroke it, and lift his hand, simultaneously pleased and nervous when he moves - is he going to wake? - and kiss that.   Each little kiss is a memory of that conversation with my mother.  They feel more vulnerable in their sleep, tucked up in their warm safe beds, than at any other time, and I feel acutely, painfully aware of that vulnerability.

But I push that pain away, down into the depths of my self.  I ignore the knowledge.  Don't look at it, don't speak about it.  Pretend it isn't there.

I can't keep them safe.

And, somehow, I know that every other parent, even though we never talk about it, feels it too.