MATERNAL PROXIMITY AND INFANT CO2 ENVIRONMENT DURING BEDSHARING AND POSSIBLE IMPLICATIONS FOR SIDS RESEARCH

Sudden infant death syndrome (SIDS) is the leading cause of human infa nt mortality after the neonatal period in Western countries, Recently, child care practices have been shown to be important in determining i nfant vulnerability to SIDS. However, very little is known about the i mpact of parent-infant cosleeping on infant sleep physiology and behav ior and SIDS risk. This reflects the failure of Western societal resea rch paradigms to appreciate the human infant's evolutionary history of cosleeping, the recency of the emergence of solitary infant sleeping as a practice and the fact that parent-infant cosleeping is still the preferred sleeping arrangement for the majority of contemporary societ ies, Incorporating current hypotheses on the mechanisms of SIDS, we ha ve hypothesized that the comparatively sensory-rich cosleeping environ ment might be protective against SIDS in some contexts, As a first ste p to characterize cosleeping environments, this investigation is aimed at assessing, in routinely bedsharing mothers and infants, their rela tive sleeping positions and the potential for sleeping in close face-t o-face proximity and for infant exposure to increased environmental CO 2 produced by maternal respiration, The latter is important in that br eathing elevated levels of CO2 can have diverse effects, ranging from respiratory stimulation at low levels to suffocation at very high leve ls. Two related laboratory studies were performed, In the first, all-n ight videotapes of 12 healthy, routinely bedsharing mother-infant pair s were analyzed for sleeping positions and time spent in face-to-face orientation and distances separating their faces, Infants were 11-15 w k old. Mothers predominantly positioned themselves on their sides faci ng their infants, with the infants placed either supine or on their si des. Mothers and infants slept oriented face-to-face for 64 +/- 27% (S ,D.) of non-movement time, with distances less than 20 cm commonly sep arating their faces. In the second study, concentrations of CO2 in air were measured in six young women at distances of up to 21 cm from the ir nares, Peak expiratory CO2 concentrations remained above 1.0% at di stances up to 9 cm and above 0.5% at 18 cm. Both baseline and peak CO2 levels were further increased at all distances when measured within a partial air pocket created to simulate a bedding environment sometime s seen during bedsharing, We conclude that during bedsharing there is potential for 1) a high degree of face-to-face orientation and close p roximity and consequently 2) increased environmental CO2, as a result of maternal respiration, to non-lethal levels that might stimulate inf ant respiration. The close proximity would also maximize the sensory i mpact of the mother on the infant through other modalities. We also su ggest that bedsharing may minimize prone infant positioning, a known r isk factor for SIDS. (C) 1997 Wiley-Liss, Inc.