According to the results, preterm neonates born to heavy-smoking mothers who smoked more than 10 cigarettes per day lead to disrupted sleep structure and sleep continuity-from 7 p.m. to 8 a.m. they slept almost two hours less than controls who were born to non-smoking mothers, and their sleep was more fragmented.
As compared with controls, neonates born to both heavy and low smokers displayed more body movements and, as a result, more disturbed sleep.
Frederic Telliez, principal investigator, and professor of neuroscience at the University of Picardie Jules Verne in Amiens, France said that sleep integrity is critical in the brain development of neonates.
Also, he said that the disruption of sleep mechanisms by prenatal smoking exposure may predispose neonates to alterations in some physiological function (such as ventilation) and can result in long-term neurocognitive disorders.
The authors said that abnormal sleep processes might alter compensatory responses to autonomic cardiovascular/respiratory challenge and increase the likelihood of life-threatening events later in life.
Prenatal smoking exposure can lead to deficits in sustained attention and impulsivity in adolescence and a higher risk of attention-deficit/hyperactivity disorder in childhood.
Such effects could be partially mediated by sleep changes. Prenatal smoking exposure is also highly related to sudden infant death syndrome (SIDS).
"The developing brain is known for its plasticity and ability to reorganize in response to the stimulation provided by the postnatal environment," said Telliez.
He added: "Consequently, it is possible that these neonates, if they are not exposed to smoking after birth, could recover and develop normal sleep structures."
For the study, the researchers recruited 40 healthy preterm neonates (postconceptional age approximately 33.9 weeks) from the neonatal intensive care unit at Amiens University Medical Center in France.
It was found that the neonates born to heavy-smoking mothers had a significantly lower mean birth weight than controls. Their average weight of 2.92 pounds was 21 percent less than the average weight of controls, which was 3.69 pounds.
Neonates born to mothers who smoked less than 10 cigarettes per day had a birth weight that was 11 percent lower than controls, although this result did not achieve statistical significance.
The study also found that even after 29.7 days without postnatal exposure to smoking or nicotine, and despite the fact that neonates in the heavy-smoking group were nearly 10 days older, infants exposed in utero to high levels of smoking still showed an altered organization of the various behavioral states.
The researchers said that examining the neurodevelopmental trajectories of neonates exposed to maternal smoking (and of those who were not) could lead to greater understanding of potential deficits in the exposed group, better prediction of outcomes, and potentially more effective compensatory clinical interventions.
Researchers also stated that longitudinal studies are necessary to assess the persistence of behavioral state effects caused by prenatal smoking exposure.
The study is published in the latest issue of the journal Sleep.