Ref. 28538-16Baby William Hartley-Smyth is already 15 weeks old even though he was only supposed to have been born this week.

William was born weighing just 1lb 8oz, or 686g, almost four months before his due date about a fifth of a full-term average birth weight.

Now he weighs in at a healthy 6lbs 4oz, or just under 3kg, and is growing more alert by the day.

His mum Jo Hartley, 33, of Exmouth Street, Old Town, said: "William's guzzling down the milk and doing so well. He has just this week started smiling.

"He is very aware of his surroundings and likes to watch the television as he is drawn to the light I don't think he has a favourite programme yet.

"When William was born he was given a 50 per cent chance of survival, so it is wonderful to finally have him at home now.

"He has his own bedroom but at the moment he is sleeping in our bedroom in a little basket by the bed.

"It seems so weird that he was only due this week. I feel like we have had him for ages. When I see pregnant women now with large bumps it seems strange I never had the chance to get that big.

"People only just started noticing I was pregnant and then I had him. I put on only about half a stone."

Jo, who was studying sociology at Bath Spa University before she became pregnant, explained how the sudden birth came about.

"I had been in hospital with a few complications but thought I was going to go home," she said.

"I had a stomach pain and thought I was constipated.

"But instead William was born breach within an hour. It was quite terrifying."

William's home for the first few weeks of his life was an enclosed incubator that resembles a transparent plastic bubble in the Special Care Baby Unit at the Great Western Hospital, Swindon.

Jo said: "I wasn't able to touch him for a week. It was quite strange really. He looked just like a little old man."

William, who has chronic lung disease, arrived home just before Christmas but still needs to wear his nasal cannula, which administers oxygen.

"He needs to grow more lung tissue which he will do in time," Jo said. "We will go back to see the consultant in the next months and I expect William will be given an X-ray to see how his lungs are developing.

Jo's partner Mark Smyth, 40, who works for Cre8 Studios in Swindon, said: "When William was first born we spent so much time just watching the heart monitor. We spoke to him through the plastic and he gradually started to recognise our voices."

The Special Care Baby Unit cares for around 400 premature babies a year.

Alex Emery