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a Department of Women's and Children's Health, Dunedin School of Medicine, Dunedin, New Zealand
b Department of Physiology, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand
| ABSTRACT |
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METHODS. Forty infants who regularly bed shared with
1 parent
5 hours per night were recruited. Overnight video of the family and physiological monitoring of the infant was conducted in infants' homes. Infant sleep position, potential for exposure to expired air, head covering and uncovering, breastfeeding, movements, family sleep arrangements, responses to the infant, and interactions were logged.
RESULTS. All infants slept with their mother. Fathers were included in 18 studies and siblings in 4. Infants usually slept beside the mother, separated from the father/siblings (if present), facing the mother, with head at mothers breast level, touching, or with mother cradling. Median overnight breastfeeding duration was 40.5 minutes. Mothers commonly faced their infant, but infants were rarely in a position that potentially exposed them to maternal expired air. Fathers were seldom in contact with the infant during sleep. Of the 102 head-covering episodes observed in 22 infants, 80% were because of changes in adult sleep position. Sixty-eight percent of head uncovering was facilitated by the mother; half of these events were prompted by the infant. A 1°C increase in room temperature decreased infant head covering by 0.2 hours.
CONCLUSIONS. The mother-infant relationship is of prime importance during bed sharing, whether the father is present or not. The focus around breastfeeding often dictates the sleep position of the infant and mother, though room temperature may also influence this. In colder rooms infants tend to spend more time with their face covered by bedding. Frequent maternal interactions rely on the ability of the mother to arouse with little stimulation. Mothers, perhaps impaired by alcohol, smoking, or overtiredness, may not be able to respond appropriately.
Key Words: bed sharing cosleeping SIDS breastfeeding sleep position
Abbreviations: SIDSsudden infant death syndrome IQRinterquartile range
Bed sharing has been investigated in many epidemiological studies in relation to the risk of sudden infant death syndrome (SIDS). This has lead to the identification of prenatal and postnatal factors that are associated with increased risk, such as maternal smoking in pregnancy,14 maternal alcohol consumption2,3 or overtiredness,2 excess bedding,2 infants <11 weeks,24 and infants sleeping with people other than parents.5 Observational studies have reported increased breastfeeding overnight,68 continuation of breastfeeding to an older age,9 increased overnight mother-infant interactions,8,10 decreased maternal tiredness,11 and emotional benefits to the mother.11 Evaluation of this evidence led to a recent recommendation by the American Academy of Pediatrics12 for parents to avoid bed sharing with their infant as practiced in the United States and other Western countries, rather than focusing on the specific situations to be avoided. The closed questions asked in case-control studies have very limited ability to place the risk factors in a broader context. Although these studies have identified many factors that increase the risk of SIDS, they are not able to describe the dynamic nature of sleep positions or adult-infant interactions through the night.
Perceptions about the advantages or risks of bed sharing are shaped by culture. It has been reported that maternal perception of infant bed sharing as normal or problematic depends on whether bed sharing is part of the cultural norm and whether interdependency or autonomy is valued.13 Bed sharing has been investigated in the context of a sleep problem in some studies,14,15 whereas night waking and frequent feeding is regarded as normal behavior in others.1618
Whether traditional or not, bed sharing is often an integral part of an infant-centered parenting style and is perceived by parents to have substantial benefits.11,16,19 Studies in the United Kingdom and United States suggest that
50% of families spend some time bed sharing.20,21 Studies of infants who commonly sleep all night with a parent, from birth, report fewer sleep difficulties.13,22
Observational studies have been conducted with mother-infant pairs at low risk of SIDS in the controlled environment of the sleep laboratory. These studies have reported benefits such as increased breastfeeding, increased infant arousals, and synchronized mother-infant sleep patterns.6,2325 Fathers have not participated in these studies; however, bed-sharing families report that fathers are often included in bed sharing at home.26
Observational studies measuring behavior and physiology have compared bed sharing and cot sleeping in the sleep laboratory19,27 and in the home,8,28 but this confines the investigation of bed sharing to factors that can also be described in cot sleep. This present study focuses solely on bed-sharing families to describe the variety of practices as observed in the home where usual practices are most likely to occur.
The aim of this study, therefore, was to provide a quantitative analysis of the sleep arrangements and behaviors of bed-sharing families in relation to infant sleep positions and potential exposure to expired air from the caregiver, infant head covering and uncovering, maternal responses to the infant, family interactions, and the presence of multiple family members. This was to increase understanding of the risks and benefits as identified by epidemiological studies. A further aim was to identify the effect of infant age and room temperature on behaviors.
| METHODS |
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1 parent for a minimum of 5 hours per night were studied. No prenatal or postnatal complications in any of the infants were reported (questionnaire). Families were recruited through local postnatal groups and media advertising. Infants were aged 0 to 6 months and were >37 weeks' gestation (except 2 infants who were 28 and 32 weeks' gestation). There were 13 infants aged 0 to 12.9 weeks, 15 aged 13 to 19.9 weeks, and 12 aged 20 to 27 weeks. The postnatal age of the 2 premature infants was adjusted to be consistent with 40 weeks' gestation. There were 14 studies in the winter compared with 8 to 10 studies in each of the 3 other seasons. The study was approved by the Southern Regional Health Authority Ethics Committee, New Zealand (protocol No. 97/04/036). Informed consent was obtained from the parent(s) of all of the infants studied.
Protocol
Infants were monitored over 2 consecutive nights in their own home. The first night involved video recording only and, on the second, both video and physiological recording. The physiological recordings involved placement of electrodes for recording raw electrocardiogram, oxygen saturation and heart rate, abdominal and chest movements of respiratory pattern, nasal airflow, shin and rectal temperature, and level of CO2 at the infants' face. The details of these recordings have been described previously.29 Sensors were attached to the infants and recordings started by the researchers. Families were left unattended for the night. Recordings were turned off in the morning when the researchers returned.
For the behavioral recordings, a small surveillance camera (CEC-C38; Panasonic, Osaka, Japan) was mounted on a stand above the bed so that the full width and the top third of the bed were in field of view to allow recordings of the infant's movements and positioning and any infant-parent interactions. A small, handheld portable television was used as a monitor to ensure correct positioning. An infrared light source (12 volt 880 Med 50; Dennard, Fleet, United Kingdom) was mounted on the stand to reflect light off the ceiling on to the recording area. The camera was connected to an analog video recorder (AG-TL700; Panasonic) set to "long play" that allowed 15 hours of recording on a 3-hour videotape. Mothers completed a questionnaire providing demographic information and answered open questions relating to reasons for bed sharing, history of bed sharing with other children, and frequency of bed sharing.
Video Analysis
Analysis of the video data for infant sleep position, potential for exposure to expired air, breastfeeding, movements, infant head covering and uncovering, family sleep arrangements, responses to the infant, and interactions was based on video from the second night to allow synchronization with physiological measures. Custom-developed computer software (C VideoTM; Envisionology, San Francisco, CA) was used to log all of the significant events into a database with time code for correlation with the physiological readings. The database (File Maker Pro 2.0; Claris Corporation, Santa Clara, CA) was customized to provide a file for each major behavior category and subcategory. The start and finish times and code for each event were logged in the database using computer key commands. The video counter was calibrated with the real time digitized on the recording tape. Although tapes were recorded as long play they were viewed at normal tape speed.
Offline logging of data started from when the infant was asleep. Sleep was defined from the video as starting after the infant was settled for 2 minutes. Start and stop times for behavioral categories were logged into the database from this start time until the final waking of the infant in the morning. Data were logged for the infant throughout the study and for any person adjacent to the infant. For example, if both parents were in the bed and the infant slept all night on the outside of the bed, next to the mother only, data were logged only for the mother and infant.
Statistical Analyses
Descriptive data are presented for infant and parent behaviors showing the median, interquartile range (IQR), and maximum value for each category investigated. Logistic or Poisson regression was used to identify any effect of infant age or room temperature on infant or parent behavior. For logistic regression analysis, the reference category was a hypothetical infant aged 12 weeks. The room temperature was centered on 15°C, the mean overnight temperature for family bedrooms in the study.
| RESULTS |
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Ninety percent of parents in this study bed shared with their infant 7 nights per week and had started bed sharing either from the birth of their infant or within 2 weeks of the birth. Most parents (26 of 31) stated that they intended to continue to bed share with their infant after the study. In 20 of 22 families where the parents had other children, the parent(s) had also bed shared with these children. (Data were not available for 9 families regarding intention to bed share and bed sharing with previous children.)
Reasons to Bed Share
Mothers gave multiple reasons as to why they chose to bed share with their infant. The most frequent responses were that they felt it provided comfort for the infant (14 mothers), it was natural (12), it facilitated breastfeeding (11), it was convenient (10), and it promoted bonding (8). Other reasons cited were that it provided enjoyment (6), reassurance (4), comfort for the mother (3), more sleep for mother (3), and helped keep the infant warm (1).
Who Slept in the Bed?
The infant slept with only the mother in 19 of 40 studies, with mother and father in 16 studies, with mother and same gender partner in 1 study, with mother and siblings in 3 studies, and with mother, father, and siblings in 1 study. In 4 mother-infant studies, the father was present in the house, but chose not to sleep with the mother and infant (2 slept in a separate room, 1 on a mattress on the floor of the parental bedroom, and 1 slept with a toddler on a single bed pushed against the king size bed of the mother/infant). In each case, this was the family's usual practice and was not a change of sleep arrangement because of the study. All of the families slept in a double (or larger) bed except for 2 mother-infant pairs who slept in a single bed, and 1 mother-father-infant group who slept in a three-quarter bed.
Sleep Arrangement of Multiple Family Members
When the father and/or siblings also shared the bed, sleep arrangements varied, but the most common position was for the father/siblings to be separated from the infant by the mother (Table 1 and Fig 1). In 2 studies, the infant slept all night in this location having no contact with the father/sibling in the bed. In the remaining 19 studies the majority of the time was still spent in this location, with the balance (median: 33%; IQR: 13%51%; maximum: 84%) spent with the infant between the adults (Table 1). Other arrangements are given in Table 1.
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Infant-Adult Contact
It was most common for infants to sleep in some form of contact with their mother: touching only (median: 3.1 hours; IQR: 1.64.6 hours; maximum: 10.3 hours) or being cradled in the mother's arm (median: 1.2; IQR: 04.9; maximum: 8.4), but sleeping without parental contact also occurred (median: 1.7; IQR: 03.6; maximum: 8.2). The maximum values indicate, however, that individuals did sleep for long periods of time in each of the contact positions. When the infant was between the parents there was negligible contact with the father, although 1 infant spent 2.5 hours cradled by the father.
Position of Infant's Head Relative to the Mother
Infants spent most time sleeping with their head at the level of the mother's breast (median: 6.1 hours; IQR: 2.48.4; maximum: 10.6) and some time (median: 1.2; IQR: 03.2; maximum: 9.9) with their head at the same level as the mother's. Infants slept <10 cm from the mother's face for a median of 0.2 hours (IQR: 01.0; maximum: 7.4), illustrated in Fig 3, and from 10 to 20 cm for a median of 0.7 hours (IQR: 0.21.8; maximum: 5.4). Only 1 infant slept with the head higher up the bed than the mother's head (6.9 hours), and another slept with head at a level below the mother's breast (2.6 hours).
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Infant Head Covering
Table 4 shows that 80% of infant head-covering episodes, to the eyes or above, occurred as a result of inadvertent movement of 1 or both adults as they changed position during sleep; 15% of these were because of adult repositioning after feeding. The mother deliberately positioned the blankets up to the infant's eyes on 2 occasions, and the remaining 17% of episodes were because of infant movements: wriggles or head turning. Infants cleared their own face in 32% of episodes, and infant movements prompted clearing by the mother in a further 36%. Whether prompted by the infant or not, the mother deliberately cleared the infant's face in 35% of the episodes. Infant arousal during head covering led to immediate feeding 16% of the time. Of the 22 infants with head covering episodes, the infant's head remained covered on final waking for 5 infants and was uncovered between 3 and 30 minutes before final waking for 5 infants and >30 minutes before final waking for 12 infants.
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Table 5 shows that infant age had no significant effect on blanket height, but a 1°C increase in room temperature increased the time that the blankets were below the chin by 0.3 hours and decreased the time that the blankets were partially over the infants face (to the eyes) by 0.2 hours. No effect of infant age or room temperature was found for total feed time, infant contact time (separate, touching mother, or cradled by mother), level of infant's head relative to mother, mother's sleep position, or infant sleep position.
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| DISCUSSION |
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The finding that fathers frequently participate in bed sharing is consistent with parental reports.26,30 Their presence, however, does not seem to alter the mother-infant relationship but may be important with regard to bed size and space for the infant. The effect of the presence of older siblings is even less clear unless the mother's attention is distracted from the infant. Siblings sharing the bed have been shown to increase the risk of SIDS in a high-risk population,5 but the risk of siblings sleeping with infants at low risk of SIDS is unknown.
It is apparent that the success and satisfaction of bed sharing is related to the mutual orientation of infant and mother: side-sleeping at breast level and in close contact allowing minimal disturbance during breastfeeding and frequent checks on the infant. Other authors confirm this as a typical orientation in breastfeeding bed sharers25,28,31 but not in nonbreastfeeding pairs,28 suggesting that breastfeeding is an important component of "low-risk bed sharing." Breast-level sleeping, although diminishing the chance of the infant's face pressing into an adult's pillow,28 does increase the likelihood of head covering.8 Therefore, it is important to examine how uncovering occurs, because it seems more likely that the mother's actions, often triggered by the infant, rather than the infant's own movements, are effective. Further evidence from cot-sleeping infants shows that infants themselves (2.5 and 5 months old) are often unable to clear blankets from their face when sleeping prone or supine.32
The increased risk of SIDS associated with bed sharing with a mother who has consumed alcohol or is overtired2,3 may be because of the inability of the mother to act on infant cues to attend to her infant. Similar findings about methods of uncovering the head have been observed previously (Helen Ball, PhD, written communication, 2002). Because 85% of infants who experienced head covering during the night were found with their head clear from bedding at final waking, it is likely that head covering during bed sharing is underreported in case-control studies.
Prone sleeping is a well-known risk factor for SIDS, and in most SIDS prevention programs, the side sleep position is discouraged because of the risk of rolling to prone. In the bed-share context, the possibility of rolling to prone may be reduced by the positioning of the mother relative to the infant.33 In 1 case-control study,34 there were more deaths in the prone position among the cot-sleeping infants compared with the bed sharers, although similar numbers in each group were placed prone to sleep.
The observations of bed-share infants in the prone position were almost all brief, with the infant lying on the mother's chest, usually after a feed. This may not constitute the same risk to infants as sleeping prone on soft bedding where rebreathing or hyperthermia may occur.35,36 This contrasts strongly with previous results from this study, where some age-matched cot-sleep infants slept prone all night.8 Other authors report bed-share infants as having either no prone sleep at all31 or briefly on the mother's chest.25 It is not known whether parents report the latter as prone sleep.
Expired air from the mother may cause small increases in the infants inspired PCO2.37 Infants in this study spent little time with their face positioned close to and in line with mothers expired air. Indeed, it has been argued that mild hypercapnia would be protective, mildly stimulating ventilation and decreasing periodic breathing.37,38 There is no evidence that breathing mother's expirate could simulate the "repeated exposure to hypoxic conditions," which animal studies have shown to blunt the arousal response to hypoxia.39 The close contact between mother and infant and exposure to mother's expired air may pose a hazard if the mother is a smoker. Nicotine has been shown to accumulate in the air, in dust, and on household surfaces even when parents smoke only outside,40 and if the mother breathes closely over the infant, even some time after smoking a cigarette, this may increase the exposure of the infant to harmful products of cigarette smoke.
Head covering is possibly of concern as a cause of overheating. It is more likely to occur in cooler rooms, which we have reported to be typical of bed sharers (16.0°C during bed sharing versus 17.5°C 2 hours after sleep onset in adult bedrooms with cot-sleeping infants).29 The increased shin temperature of bed-share infants compared with cot-sleep infants29 is evidence of thermolytic activity induced by the thicker bedding on adult beds,29 and head covering could be a problem in this situation. In New Zealand, central heating of homes is not common despite cool winter temperatures in the south. In this study, mean bedroom temperature dropped through the night to reach 14.4°C by 8 hours after sleep onset. It may be that parents are less likely to heat the bedroom overnight if the infant is sleeping in the adult bed. Heating adult bedrooms overnight could influence the amount of and the position of bedding, helping to reduce head covering.
The side sleep position was most common for infants in this study despite the widely publicized message to avoid this sleep position. At the time of data collection, New Zealand advice was that mothers who smoked should not bed share with their infant; however, many families, particularly those of European descent, perceived a general antibed-share culture and felt that they were sleeping in a way that did not have widespread support.16,17 This alienation from mainstream practice may have led families to disregard advice that was clearly aimed at cot-sleeping infants. There were no parenting pamphlets aimed specifically at bed-sharing families with advice about safe sleeping at this time. This emphasizes the importance of establishing bed share-specific guidelines and of using appropriate strategies for reaching the target group.
| CONCLUSIONS |
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| ACKNOWLEDGMENTS |
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We thank the families who participated in the study and also Amanda Phillips and Charrissa Makowharemahihi for research assistance, Assoc Prof Sheila Williams for statistical advice, Christine Rimene for advice on cultural aspects, and Paul Bennington and Gordon Yau for assistance with customizing the database for video logging.
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Address correspondence to Sally Baddock, PhD, School of Midwifery, Otago Polytechnic, Private Bag 1910, Dunedin, New Zealand. E-mail: sbaddock{at}tekotago.ac.nz
The authors have indicated they have no financial relationships relevant to this article to disclose.
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