My son Oscar slept soundly until he was 18 months old, when we moved house for the third time since his birth and I started a new job. For six months afterwards, he woke every night at around 2am, and usually screamed for anything between one and three hours.
If we took him into bed with us, he thrashed around, moaned and prodded. If we left him on his own, he wailed and pleaded with us to come into our bed.
A new childminder, my absence, the third home in two years - all were possible reasons, but knowing that didn't help us come up with the solution. Soon my stomach clenched at the sound of Oscar stirring at night.
Work suffered, I suffered, and my husband and I started shouting at each other.
Eventually, in despair, we consulted a doctor, who was sympathetic but not very helpful. We also looked at several books, plumping for the most bossy, as it offered the only thing we hadn't tried yet - letting him scream.
We were kind but ruthless. We took turns to go into his room and reassure him that he was not alone. For three weeks we continued this battle of wills, until finally Oscar taught himself how to go back to sleep without the fireworks.
According to research by the National Sleep Foundation, there's nothing abnormal about my child suddenly turning from a peaceful sleeper into a night-time nightmare. In fact, 47% of families with children under 3 claim at least one of their children will wake at least once a night and need help to get back to sleep.
The fact is, everyone, both adults and children, wakes five or more times a night, usually when changing from one stage of sleep to another. Normally, we don't remember these episodes. But in some toddlers, at certain stages of their development, these stirrings cause them to become fully awake. Then they search for whatever they need to help them get back to sleep - usually you!
A whole new crop of issues, can appear as children grow,' says mum-of-four Elizabeth Pantley, author of The No-Cry Sleep Solution for Toddlers And Preschoolers (McGraw-Hill, £8.99).
For example, if potty training has just begun, disturbed sleep could be down to a new sensitivity to a wet night-time nappy or a full bladder, as they learn to hold on until morning. If this may be the case, encourage your toddler to go the loo a few times before going to bed.
The time that your child goes to bed could be a factor, too. If it's a bit too late, she can experience chronic sleep deprivation, which promotes fitful sleep.
Also, strange as it sounds, the sheer thrill of mastering new skills could be the cause of her wakefulness.
If the night waking has suddenly become worse, it might be that she is in the process of mastering learning to walk or read,' explains Elizabeth. These are stimulating activities, which hover in her mind.' As such, it's worth avoiding doing new activities near bedtime.
Stress, the flip side of excitement, can be a culprit, too. Some children are noticeably affected when starting nursery, weaning, or even upgrading from a cot to a bed. Also, a change in your life, such as divorce, a new job or becoming pregnant again, can all affect your child. In such cases, it's important to maintain a consistent bedtime routine.
If your child's old enough, help her to formulate a plan to cope with night waking and build her confidence in mastering getting back to sleep,' says Elizabeth. It might involve coming to your bed, taking a sip of water or cuddling a favourite animal. Security objects, like blankets or teddies, can be a great help and keep your child company when you're not there.
If your toddler wakes up crying or is very clingy, then goes back to sleep with some comforting, it's possible she's feeling anxious or even having bad dreams,' says Elizabeth.
Be observant - could your child be absorbing things in the day that may unsettle her at bedtime, resulting in nightmares, or the more extreme night terrors? Don't overreact to your child's fear but, at the same time, be sensitive to her feelings.
Another cause of wakefulness could be hunger. Toddlers have growth spurts and during these times they need more food, but that might not show itself until they are awoken by hunger pangs during the night. If you suspect a growth spurt is the cause of your child's disturbed sleep pattern, ensure that in the evening they eat plenty of foods that help promote a good night's sleep, such as carbohydrates, which have a calming effect on the body.
Finally, make sure your toddler knows night-time is for sleeping and nothing else.
Your best weapon in the early hours is to be excruciatingly boring,' says Elizabeth. So don't turn on lights, rock her, sing songs, talk, offer food or milk, and never turn on the TV.
You can soothe her and settle her back into sleep,' she suggests. But once she's settled it's important to separate yourself from her. Remain in the room, but don't engage. Sometimes simply your presence will be enough.'
If the waking shows no sign of stopping, seek medical advice. It's thought that long-term sleep deprivation may affect your child's mood and behaviour, health, learning and even sleep in later life, so don't be afraid to ask for help if you need it.