The story so far: Josa Young has 2 children aged eleven and eight. She’s now 41 and expecting another baby. She’s 20 weeks pregnant and keeping a diary Whoops, I looked

I go for my routine anomaly scan with Archie. Two young women are doing the scanning and keep emphasising that I only get twenty minutes every time I ask a question. Having had the nuchal fold scan, I was expecting a little more detailed attention due to my age – looking for what are called the soft markers for Down syndrome and other problems. Not a bit of it. They flipped through the chart, chatting amongst themselves, and generally making me feel as if I was slightly in the way.

Archie was very interested, but didn’t like it much because, at this stage, it is the baby’s bones that show up on the screen – and skeletons alarm him. They asked at one point if I wanted to know the baby’s sex. Oh dear, I can only say in my defence that Archie tempted me, and I fell. They flipped up the image and the evidence that we are having another little boy was all too obvious.

I felt extraordinary. I had never known this before birth, although I had guessed from such things as the speed of heartbeat. I’d assumed it would be a girl because of the feeling of sickness this time, as I did with Maud, but not with Archie.

Also, if I had ovulated at my normal time then, from rough calculations, the sperm would have had to be very long-lived to fertilise the ovum. And they say that XY or female sperm are a lot tougher than YY or male ones. If you wish to choose the sex of your baby – a futile one this – then the advice is always to make love bang on ovulation for a boy, and a few days before for a girl. If any of this holds water, then I did ovulate very early as suspected.

I had to let the potential little girl, along with her list of poetical names and her cute outfits, vanish from my imagination. I regretted little Edith or Esme or Violet. Maud kindly tells me I can keep dressing her if I need a living doll. Archie is of course thrilled and looking forward to long Lego sessions in a rosy future. He wants to call his little brother Sebastian or Benedict.

The session ended, and I wiped off the jelly and went out clutching the little printed photo showing the baby’s skeletal face and arm. I felt very dissatisfied and restless and rather guilty about peeping at my present before Christmas.

The terrible worry factor

It got worse at home when I looked at the charts they had filled in, in my hand-held notes. There are graphs showing where the baby’s measurements lie in relation to the average. One measurement stood out – the baby’s head seemed to be well below average in size – and small for his dates. Now, as a family, both sides have huge heads. Not easy for buying hats, and very characteristic.

Ultrasound is notorious for its anxiety-inducing function – and it was certainly happening to me. I wept with worry, and Thoby, who takes it all so much more in his stride, rang my hitherto unseen obstetrician. He was very reassuring, but I wanted another scan to check. We offered to go private for this one, anything for a bit more personal attention. We were booked in immediately for that afternoon.

Quite different – two highly qualified doctors in the room, careful measurements taken, every question answered. We could even see the blood flowing around the baby’s heart in vivid colour. The head measurement this time was bang on average. There were no ‘soft markers’ but there are no certainties either – just more statistics of probability, possibly as low now as one in 1,000. At this point I have stopped fiddling around and think I will just get on with the pregnancy.

See Anastasia's pregnancy diary for weeks 20-22.