Mothers who are struggling to get their babies to sleep should consider how much caffeine they are consuming, according to a breast feeding expert.
Drinking coffee, tea and soft drinks and even eating chocolate increases the level of the stimulant in the blood. Babies can become restless, awake and irritable, when it is passed on through a mother's milk.
Dr Ruth Lawrence, editor of the journal Breastfeeding Medicine, said that babies have difficulties in breaking down and removing the drug from their bodies especially in their first two weeks of life. This can lead it to accumulate causing adverse symptoms.
'Usually a mother, particularly if she is breastfeeding, is cautioned to limit her caffeine intake,' she told the Journal of Caffeine Research.
The professor from Rochester University in New York, added mothers should 'try to void the excesses that might really add up to a lot of caffeine.'
But how many cups of coffee constitutes an 'excessive amount'? According to Dr Lawrence it depends on the individual mother.
As a general practice mothers are advised not to have more than 300mg of caffeine - equivalent to three cups of coffee - a day.
However, Dr Lawrence said: 'Unfortunately a lot of things about breastfeeding are based on opinion, and I do not know that the 'safe' amount of caffeine for daily use has been carefully measured.
'We had a case here in which a child was brought in, thought to be having seizures and was headed for the million-dollar workup, the EEG, the MRI, the works.
'In the emergency room we drew a caffeine level. It was off the charts! Taking a history from the mother, she said "oh year, I drink coffee all the time. I have a cup ready for me all day long. Is that a problem?"
Dr Lawrence said they learned about the dangers of caffeine and newborns after using it to stimulate breathing in babies in neonatal intensive care.
'We discovered that we overdosed them very quickly. Now they are only dosed once a day in order to keep their levels under control because the metabolism is so poor.'
She said the cases she had come across could be indicative of a more widespread problem and that new mothers needed to know about the risks.
She added: 'Some individuals are more sensitive than others. It would be a good starting point if a child is very restless, that one might consider reducing the intake of caffeine.'