New Delhi, Jan. 25: Low levels of dream-laden sleep in women during the third trimester of pregnancy may make their babies susceptible to emotional distress, a study by Indian scientists on rats and their pups has suggested.
The scientists, in a government research centre in Thiruvananthapuram, have said their study is the first to show a link between loss of sleep with rapid eye movements (REM) — the dreaming phase of sleep — and care-seeking cries by newborns.
The scientists examined patterns of high-frequency ultrasonic calls newborn rat pups emit when separated from their mothers during the first three weeks after birth, similar to the cries of human infants. They found that pups born to rats deprived of REM sleep during the third trimester of pregnancy called out less and that their cries were blunted compared with those of pups whose mothers had normal REM sleep.
“The differences in their cries were striking,” Kamalesh Gulia, a senior scientist at the Sleep Research Laboratory in the Sree Chitra Tirunal Institute of Medical Science and Technology (SCTIMST) who led the study, told The Telegraph.
The pups whose mothers had low levels of REM sleep appeared less responsive to their mothers’ absence which, Gulia said, may indicate some distortion in normal social bonding with their mothers. The study has been published in the journal PLOS One.
Earlier studies in animals and humans have hinted that the offspring of expectant mothers with compromised sleep may exhibit what appear to be signs of anxiety disorders, but the effects of maternal REM sleep loss on newborns have remained unexplored.
Sleep typically occurs in about 90-minute cycles of non-REM and REM phases. Early during sleep, non-REM makes up about 75 minutes while REM lasts about 15 minutes. But the REM component grows during the night and, by early morning, makes up about 30 to 40 minutes.
“It’s been known for some time that maternal sleep deprivation can be detrimental to the newborn,” said Nihar Ranjan Jana, a senior scientist at the National Centre for Brain Research, Manesar (Haryana), who was not associated with the Sree Chitra study. “This work is trying to probe the mechanisms through which sleep deprivation affects by examining how the REM component of sleep affects the newborn.”
Independent research in the past has suggested that REM sleep stimulates the regions of the brain involved in the process of learning. The changes in the pups’ calls suggest that maternal REM sleep deprivation may in some influence the emotional behaviour of newborns.
“The prenatal mechanisms that may explain this effect remain unclear,” Jana said.
The researchers believe the findings may have implications for humans.
“Many expectant mothers don’t get as much sleep as they should,” Gulia said. “While we cannot consciously control REM sleep, the longer the duration of sleep, the greater is the probability of getting REM sleep episodes.”
She said women in the third trimester of pregnancy should also try to make their sleeping positions as physically comfortable as possible to reduce the risk of physical discomfort from disturbing their sleep and contributing to the loss of REM sleep.
The Sree Chitra team also observed that pups whose mothers had normal REM sleep reduced their frequency of calls from day 13 onwards prior to normal weaning on day 21. But the calls by pups whose mothers had been deprived of REM sleep did not decrease at the same pace.
The scientists suspect this inability to reduce calls just before weaning may “reflect a subtle delay in brain development” which continues in the pups in the three weeks after birth. The SCTIMST team plans to continue tracking the behaviour of the pups into adulthood.