Among the great debates in parenting is the decision of where babies will sleep: In the parents' bed? In a crib next to the parents' bed? In another room?
A recent study shed a little light on how infants breathe when sleeping in their parents' bed compared to sleeping in a crib on their own.
While there are some increased risks when parents share their bed with their baby, these risks generally only become significant when other risk factors for sudden infant death syndrome are also present.
Sally A. Baddock, PhD, of the Departments of Women's and Children's Health and of Preventive and Social Medicine at the University of Otago in New Zealand, led a study comparing breathing patterns and oxygen levels in babies when bed-sharing versus sleeping alone.
The somewhat small study involved 40 healthy babies, from newborn up to 6 months, who regularly slept in their parents' bed - called "bed-sharing" - for at least 5 hours a night.
These 40 were compared to 40 other healthy babies of the same age who slept in their own cribs instead of their parents' bed.
The babies had similar ranges of birth weight, current weight and gestational age (how many weeks of pregnancy before they were born).
The mothers of the babies were similar ages and all had at least some college, and nearly all the babies were breastfeeding. One significant difference was that only 8 percent of the bed-sharing moms smoked during the second trimester of pregnancy compared to 25 percent of the crib-sleeping babies' mothers.
For one night, the researchers used an infrared video to watch parent and baby behavior during their sleep.
They also fitted the babies with devices to measure the babies' temperature throughout the night, the level of oxygen carried in their blood while asleep and how much carbon dioxide was around the babies' faces.
The researchers counted how frequently the babies' level of oxygen saturation dropped below 90 percent. They also counted how frequently the babies "rebreathed," which means the baby breathes in the same air they just exhaled instead of getting fresh air.
The findings revealed that the bed-sharing babies had about twice as many "desaturation events," or times when the baby's oxygen saturation dropped below 90 percent (255 times compared to 123 times).
The researchers were able to determine that part of the reason for these desaturation events was due to the warmer environment immediately around the baby when sharing a bed with parents.
Most of these desaturation occurrences happened right after the baby paused in breathing for 5 to 10 seconds while asleep.
The researchers reported that any pauses in breathing for more than 15 seconds was rare. It only happened three times in the bed-sharing infants, and six times in the babies sleeping in cribs.
Likewise, the blood saturation levels for the babies only dropped below 80 percent three times in the bed-sharing babies and four times in the crib-sleeping babies.
The researchers found that 80 rebreathing episodes occurred where the baby breathed in the air he or she had just exhaled, but nearly all of these occurred after the baby's head had been covered.
In most situations, the mother removed the covering, and the researchers noted that a mother who had taken sedatives or alcohol may be less able to help her infant in the night if this were to happen.
There were 22 bed-sharing babies and one crib-sleeping baby who accounted for these 80 episodes, but the oxygen levels for these children never dropped below 97.6 percent even during the rebreathing episode.
The authors acknowledge that a number of parents and various culture prefer bed-sharing for young babies because they believe it helps with bonding, breastfeeding, reducing a baby's stress and ensuring mom gets enough sleep.
Many pediatricians discourage the practice, however, because of concerns about the higher risk for sudden infant death syndrome (SIDS).
The primary risk factors for SIDS are the mother smoking during pregnancy, either parent drinking or taking sedatives, extreme tiredness in the parents, sleeping on a couch and extra bedding. Pediatricians also advise parents to put babies to sleep on their back instead of their stomach.
Among the things that have been shown to reduce the likelihood of SIDS are ensuring the baby is not in a room exposed to tobacco smoke, using a fan and giving the baby a pacifier during sleep.
In this study, the authors pointed out that bed-sharing has pluses and minuses.
"The presence of the mother and other bed-partners, and the physical environment of the adult bed clearly led to a different sleep environment for the bed-sharing infant compared with the crib-sleeping infant, resulting in beneficial and potentially compromising situations," the authors wrote.
Because the bed-sharing babies in this study were healthy and at low risk for SIDS, the authors concluded that their rebreathing and oxygen desaturation events did not likely put these babies at risk for SIDS.
They did say that a baby with other risk factors present may have been at greater risk for SIDS if bed-sharing than if sleeping in his or her own crib.
According to William Kohler, MD, director of Pediatric Sleep Services at Florida Hospital Tampa, the drop in the babies' oxygen level concentrations, called "hyperemia," could be an additional SIDS risk factor, but it's hard to tell without more specific information about each infant's circumstances.
"We don't have enough details to exactly see how many, how often and how low it got for what period of time, but that hypoxemia can be an additional factor leading to SIDS," he said. "There are many factors involved in sudden infant death."
He said the "triple model" for SIDS includes a pre-existing (genetic) component and an external event that could occur which the baby cannot overcome. (The third part of the model is the baby's young and vulnerable developmental stage before he or she can effectively manage their body functions, like breathing.)
"These particular infants that were bed-sharing did have potential problems compared to the non-bed-sharing child. There is some compromise of good air exchange, and that is a potential risk factor for sudden infant death if other factors are present," Dr. Kohler said. "However, in this particular situation, these children were at low risk based on other factors, and even though they did have these events, they were not critical in potentially causing the child to have SIDS."
The study was published July 16 in the journal Pediatrics. The research was funded by the Health Research Council of New Zealand, a University of Otago Research Grant and a Fanny Evans Scholarship. The authors reported no conflicts of interest.