This study included 40 routinely bedsharing infants and 40 routinely crib-sleeping infants, all of which were healthy and between 0 and 6 months old. Few mothers in the study were smokers, and most of them breastfed.
The infants and mothers were videotaped on two consecutive nights. On the second night, the babies were also fitted with several sensors for physiological measurements. Their blood oxygen was measured by pulse oximetry. Other sensors measured breathing rate, and thermometers measured body temperature during the night. The air in the space directly around the infant was also sampled periodically through a small tube attached to the infant’s face. Although these measurements bring to mind a picture of lots of tubes and wires, the authors say, “All leads were secured to allow mothers to handle infants freely during the night.”
The purpose of the study was to better understand the breathing environment for bedsharing and crib-sleeping infants. Specifically, the study reported two main measures:
1. Desaturation events. Oxygen saturation is a measure of the percentage of arterial blood cells that are carrying oxygen. The higher the percentage, the more oxygen is circulating in the body for cells to use. Oxygen saturation of 95-100% is normal, and baseline measured in the infants in this study was 97.6%. A desaturation event was counted if oxygen saturation dipped below 90% for at least one second, indicating a period of low oxygen availability for the baby.
2. Rebreathing events. A rebreathing event was noted if the carbon dioxide in the air around a baby’s face increased above 3%. Carbon dioxide is normally 0.039%, so 3% is very high. This is called a rebreathing event because it indicates that the baby must be breathing air that had just been exhaled (and therefore higher in carbon dioxide and lower in oxygen), either by the baby or the mother. It usually occurs if the baby’s head becomes covered by something like a blanket. We know from previous infant studies that if the carbon dioxide level in the air gets above 3%, babies will increase their rate of breathing to try to return their body to normal carbon dioxide and oxygen balance .
The authors wondered if babies sleeping in beds next to their mothers or alone in cribs would be exposed differently to these minor respiration challenges.
Here’s what they found:
On average, babies that slept in cribs had 3.1 desaturation events per night, while bedsharing babies had 6.8. In the bedsharing babies, many these periods of low oxygen availability were associated with warmer body temperatures.
During the study, only one crib-sleeping infant had a rebreathing event. This occurred when a muslin swaddle ended up around the baby’s face for part of the night. Among the 40 bedsharing infants, 22 of them had a total of 79 rebreathing events. During the rebreathing events, the babies’ respiration rates and heart rates increased, but their oxygen saturation did not change. In other words, the babies seemed to be able to respond appropriately to the challenge of high carbon dioxide to maintain their blood oxygen at normal levels.
Why did the bedsharing infants have so many rebreathing events? Some of them happened because the infants were sleeping on their tummies, in the prone position. In one case, a mother was breathing directly into her infant’s face as they slept together. However, 70% of these rebreathing events happened because the infants’ heads were covered with blankets. The same authors reported in an earlier paper  that head covering usually occurred when an adult shifted body position during the night and that most of the time (but not always), mothers eventually ended up uncovering their babies’ heads.
OK, so bedsharing infants face more breathing challenges during the night. What does this mean? Is it a problem? Does it have any relevance to the risk of SIDS?
In this study, these low-risk, healthy infants seemed to respond appropriately to breathing challenges. When they were exposed to high carbon dioxide, they increased their respiration rate in order to get more oxygen and blow off carbon dioxide. When their faces were covered, their mothers often uncovered them, sometimes in response to the baby waking and crying. The truth is that we don’t know if these minor challenges pose a real risk to healthy infants.
But what happens if the baby is sick, premature, or has been exposed to cigarette smoke? These factors may affect a baby’s ability to respond appropriately to high carbon dioxide or low oxygen. What if the mother is less responsive due to drugs or alcohol? She may not wake when the baby signals distress. The authors also point out that repeated exposure to low oxygen, as happens during the desaturation events, has been shown to blunt arousal responses in animals. They state, “We suggest that frequent desaturations in vulnerable bedsharing infants could be a contributory factor in their risk for SIDS.”
The authors of this paper conclude with the following statement:
“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 bedsharing infant compared with the crib-sleeping infant, resulting in beneficial and potentially compromising situations. Infant homeostatic responses and frequent maternal interactions seemed to keep these low-risk infants safe. However, we suggest that it is potentially hazardous for an infant to sleep in the same bed as their parent, if the infant and/or mother are unresponsive. We acknowledge that bedsharing is a practice valued by many; thus, it is important to identify the specific dangers related to this practice… Studies with high-risk infants are required to advance understanding of the specific mechanism(s) leading to their increased vulnerability.”
We know that SIDS occurs more often in babies that bedshare. We also know that the risk is clearly higher in babies that are very young (<3 months), babies exposed to smoking, those sleeping in beds with lots of loose bedding, and those sleeping with adults that are impaired by alcohol or drugs . Routine bedsharing does not seem to increase the risk of SIDS .
Many parents choose to bedshare because they enjoy the closeness to their babies, because it makes breastfeeding easier, and sometimes because their babies refuse to sleep any other way. Bedsharing is also the norm in many cultures around the world. Increasing our understanding of the physiology of babies sleeping together and apart from their parents will only help us to understand and minimize the risks associated with SIDS.
If you bedshare, this study illustrates some important cautions:
- Minimize bedding and pillows in your bed. When is someone going to make an adult-sized, zip-up sleep sack for the breastfeeding mother?
- Take care to keep your baby from getting overly warm.
- No smoking during pregnancy or while the baby is bedsharing (even smoking outside the bed increases the risk).
- Avoid drugs and alcohol, which can impair your ability to respond to your baby during the night.
If you bedshare, do you worry about the risks? What do you do to keep your baby safe during the night?
1. Baddock, S.A., et al., Hypoxic and Hypercapnic Events in Young Infants During Bed-sharing. Pediatrics, 2012.
2. Haddad, G.G., et al., CO2-induced changes in ventilation and ventilatory pattern in normal sleeping infants. J Appl Physiol, 1980. 48(4): p. 684-8.
3. Baddock, S.A., et al., Sleep arrangements and behavior of bed-sharing families in the home setting. Pediatrics, 2007. 119(1): p. e200-7.
4. Task Force on Sudden Infant Death Syndrome – American Academy of Pediatrics, SIDS and other sleep-related infant deaths: expansion of recommendations for a safe infant sleeping environment. Pediatrics, 2011. 128(5): p. 1030-9.
5. Vennemann, M.M., et al., Bed sharing and the risk of sudden infant death syndrome: can we resolve the debate? J Pediatr, 2012. 160(1): p. 44-8 e2.