Parents should avoid comforting their babies when they wake and cry at night because self-soothing is critical for babies to learn how to regulate their own sleep, so says a developmental psychologist who has recently completed a study on the subject.

Professor Marsha Weinraub from Philadelphia’s Temple University studied the sleeping habits of more than 1200 babies between the ages of six to 36 months and asked parents of the infants to document their child’s awakenings at four stages during their development, namely at six, 15, 24 and 36 months.

Weinraub found that sleeping patterns could be split into one of two separate groups: sleepers (those who slept through the night during their development) and transitional sleepers (those who did not).

Research shows that by the time babies reach their six-month developmental mark most will have learnt to sleep through the night (waking their mothers once per week) but not all infants follow this developmental guide.

Just like adults, babies shift through a new cycle of sleep every one-and-a-half to two hours and during this shift, some will momentarily wake before falling back to sleep again.

Those babies who were noted as having transitional sleeper patterns awoke at least seven nights a week. The frequency later dropped to just two nights per week by the age of 15 months and then finally once a week at 24 months.

Transitional sleepers were also inclined to have higher scores on tests that regarded irritability and distractibility as having a difficult temperament.

Weinraub found that more baby boys were transitional sleepers and were more likely to have been breastfed. Their mothers also had a higher incidence of postpartum depression.

"The best advice is to put infants to bed at a regular time every night, allow them to fall asleep on their own and resist the urge to respond right away to awakenings," Weinraub advised.