Teething can add a whole new layer to the meaning of "sleeping like a baby". From around 3-12* months, babies begin to develop their first teeth and it’s normal for even a champion snoozer to experience a disruption in their regular sleep patterns.
While your baby is teething, it’s common for tender gums to cause more crying than normal, fussing and interrupted sleep. You can help ease their pain by offering a teething ring or gently running a finger along their gum. Or if your little one wakes at night, try offering some gentle words for comfort or singing a lullaby
* The baby book. ISBN 9780316198264 (p506507).