Some nights Mary McCabe doesn't get a chance to tuck her children into bed and read them a story. Some evenings she's not there to help them with their homework. At Christmas, like thousands of other nurses, Mary is hard at work on the night shift, missing out on the excitement at home.

Mary, who lives in Athlone, Co Westmeath, works in the coronary care unit in Tullamore General Hospital, Co Offaly. Like most nurses she is on a rotation system and every three months or so she works a minimum of a month of nights. On those occasions, her husband Alan, who works nine to five, Monday to Friday, has to do all the babysitting and look after Ewan (9), Vanessa (4) and Olivia (3).

When she is on day duty Mary works from 8 a.m. to 9 p.m., and when she is on nights her shift starts at 8.30 p.m. and finishes at 8 a.m.

When she works days, because they are so long, she works three days out of every seven, whereas on nights she works seven nights in a fortnight.

Which is better in terms of the children? "Well, day duty is obviously a lot better. It is more normal because they are going out during the day as well, rather than me leaving them at night when they are coming home. For family living, day duty is preferable."

Night duty means catching up on sleep during the day - and weekends in particular are tough when the children are there and Mary needs to sleep.

"They're here in the house and children must be children and while they try their best to be quiet, they can't. My husband occupies them with as many games as he can, colouring books and things like that, but they would be singing and dancing and shouting. You can't get sleep at the weekends now."

During the week they go to their babysitter during the day and come back in the evening. When the children come back at 4 or 5 p.m. it is still only morning for Mary and they are working from opposite ends of the clock. While the children may want to chat, Mary will probably be exhausted and in need of some proper sleep.

This year, she worked nights in June and August and the sleep deprivation was worse because of the brighter days and an increased noise level from the children, courtesy of their school holidays.

"Of course when the days are bright and they are on their summer holidays, they want you to be up and about and going places with them and obviously you can't," she explains.

Mary isn't the only one affected by her variable shifts. It affects the children too, and Ewan's football training in particular.

Training is on Fridays and matches are on Saturdays. Because Mary can't always bring him, he has to be brought by someone else or he has to miss out.

"That can be difficult because he obviously misses out on that. He falls behind and that part of his development is important for him. If he doesn't keep up with his training then obviously he isn't as strong as the other players in the team."

It upsets Ewan when he doesn't get a place or the position in the team he was hoping for. However, he doesn't complain, she says.

Mary finds, particularly if one child is sick, it is difficult leaving them at night. If anything happens, she can't be there on the spot - she is 32 miles away.

She says that when the children were toddlers they didn't understand that their mother had to work at night. Mary had to try her best to hide or disappear quietly so they didn't know she had left the home at all.

"You miss out on giving them cuddles going to bed at night."

Correction: Last week's Real World article about Asperger's Syndrome was written by Fiona Murdoch, not Elaine Larkin as stated.