The epidemiology of sudden infant death in upstate New York: II: birth characteristics.

This study describes the epidemiology of sudden infant death syndrome (SIDS) among infants born during 1974 to upstate New York residents. Birth certificate characteristics for 184 SIDS cases are compared with those of 417 infants dying from other causes in the same age range, 7-365 days. The results confirm the following as infant risk factors: fall or winter birth, low birthweight for gestational age, twin birth, and live birth order three or more. Maternal risk factors include: age under 20, abnormal uterine bleeding during pregnancy, late initiation of prenatal care, less than 12 years of education and single marital status. The increased risk for mothers who first gave birth in their teens and for second-born twins has not been previously reported. The evidence that SIDS babies are small for gestational age, that twins, especially the second born, and babies whose mothers experienced abnormal uterine bleeding during pregnancy are all at increased risk of SIDS suggests that perinatal stress leading to hypoxia is one of the components that determine the risk of SIDS.     

Timing of prenatal care and risk of sudden infant death syndrome

Sudden infant death syndrome (SIDS) is the leading cause of death during post-neonatal life. Mothers whose infants succumb to SIDS are reported to initiate prenatal care later than control mothers. Previous studies have not always controlled for socioeconomic status (SES) of mothers or other potential confounders such as gestational age or birthweight of infants. The purpose of this study was to assess whether timing of prenatal care adjusted for these potential confounders was an independent risk factor for SIDS. SIDS cases (N = 148) were identified from the Upstate New York livebirth cohort for 1974 (N = 132,948) and compared to randomly selected controls (N = 355) who were frequency-matched on maternal age, race, parity and residence and infant's birth date. Data were abstracted from matched vital certificates (97% response), hospital delivery records (89% response) and selected sample of autopsy reports (100% response). Odds ratios (OR) and 95% confidence intervals (CI) were obtained using unconditional logistic regression. A significant inverse relationship was observed for number of prenatal visits and risk of SIDS; a significant direct relationship was observed between trimester prenatal care initiated and risk of SIDS. The results suggest that timing of prenatal care is important in assessing SIDS risk even after adjusting for potential confounders of early prenatal care utilization.     

Prenatal and intrapartum events and sudden infant death syndrome

The purpose of this study was to evaluate specific pregnancy and labour and delivery events that may increase the risk of sudden infant death syndrome (SIDS). A matched case-control study was conducted in five counties in southern California, using California death certificate records. The sample consisted of 239 Caucasian, African-American, Hispanic and Asian mothers of SIDS infants and 239 mothers of control infants matched on sex, race, birth hospital and date of birth. Mothers participated in a detailed telephone interview and provided access to obstetric and paediatric records. More case than control mothers reported a family history of anaemia (OR=2.12, P < 0.001). Placental abruptions were strongly associated with SIDS (unadjusted OR=7.94, [95% CI 1.34,47.12]). There was an increased risk of SIDS death associated with maternal anaemia during pregnancy (OR=2.51, [95% CI 1.25,5.03]), while simultaneously adjusting for maternal smoking during pregnancy, maternal years of education and age, parity, infant birthweight, gestational age, medical conditions at birth, infant sleep position and post-natal smoking. Interactions of anaemia and prenatal smoking as well as anaemia and post-natal smoking were not statistically significant. There were no other statistically significant differences between case and control mothers for pregnancy conditions, labour and delivery events (e.g. caesarean sections, anaesthesia, forceps) or newborn complications (e.g. nuchal cord, meconium aspiration). Anaemia and placental abruptions were significantly associated with an increased risk of SIDS; both are circumstances in which a fetus may become hypoxic, thereby compromising the subsequent growth, development and ultimate survival of the infant.     

Risk factors of sudden infant death syndrome and risk factors for sleep disturbances

Relationship between major risk factors of sudden infant death syndrome (SIDS) and sleep disorders in the infants is the subject of review and discussion. Improper micro‐environmental characteristics (especially poor environmental organisation and lack of developmental stimulation), pre‐term delivery and/or infant low birth weight, prone sleep position, maternal smoking during pregnancy, and infant–parent(s) bed‐sharing are among well‐established risk factors of SIDS. These factors may also be associated with sleep disorders in infants, principally with bedtime problems, abnormal night awakenings, and arrhythmic sleep. As an attempt to fix sleep problems, some inexperienced parents may try infant‐rearing practices that may only aggravate sleep troubles and lead to further increased risk of SIDS, thus giving start to a vicious circle. Health care providers need to be aware of such situations as an opportunity to provide parents with guidance with respect for individual infant and family characteristics.     

Health Messaging and African–American Infant Sleep Location: A Randomized Controlled Trial

Infant-parent bedsharing increases the risk of SIDS and other sleep-related deaths. Despite AAP recommendations to avoid bedsharing, public health efforts have been unsuccessful in changing behaviors. African–American infants are more than twice as likely to die from SIDS and other sleep-related deaths, and are also twice as likely to bedshare with their parents. Further, African–American parents have a high degree of self-efficacy with regards to preventing infant suffocation, but low self-efficacy with regards to SIDS risk reduction. It is unclear whether messages emphasizing suffocation prevention will decrease bedsharing. To evaluate the impact of specific health messages on African–American parental decisions regarding infant sleep location. We conducted a randomized, controlled trial of African–American mothers of infants. The control group received standard messaging emphasizing AAP-recommended safe sleep practices, including avoidance of bedsharing, for the purposes of SIDS risk reduction. The intervention group received enhanced messaging emphasizing safe sleep practices, including avoidance of bedsharing, for both SIDS risk reduction and suffocation prevention. Participants completed interviews at 2–3 weeks, 2–3 months, and 5–6 months after the infant’s birth. 1194 mothers were enrolled in the study, and 637 completed all interviews. Bedsharing, both usually (aOR 1.005 [95 % CI 1.003, 1.006]) and last night (aOR 1.004 [95 % CI 1.002, 1.007]) increased slightly but statistically significantly with infant age (p < 0.001). Receipt of the enhanced message did not impact on sleep location. Maternal belief that bedsharing increased the risk of SIDS or suffocation declined over 6 months (p < 0.001) and did not differ by group assignment. African–American mothers who received an enhanced message about SIDS risk reduction and suffocation prevention were no less likely to bedshare with their infants. Clinical Trials Registration: Clinical Trials.gov identifier NCT01361880     

Maternal smoking, birthweight and gestational age in sudden infant death syndrome (SIDS) babies and their surviving siblings

To evaluate the effect of maternal smoking on intrauterine growth of babies who died of sudden infant death syndrome (SIDS), birthweights of SIDS infants and their surviving siblings were compared with birthweights of infants in sibships were all infants survived the first year of life. We studied 184 349 mothers with at least two births registered in the population-based Swedish Medical Birth Registry during 1983–91. The mother being the unit of analysis, birthweight and gestational age of her infants were the repeated measures used in a repeated measures analysis of variance. Mothers whose first two infants survived at least 1 year, smoked less than mothers of SIDS infants, 25 and 41% ( P < 5 0.01). Overall, SIDS mothers did not smoke more while pregnant with the SIDS infant than while pregnant with the surviving sibling. SIDS siblings weighted, on average, 90 g less than infants in non-affected sibships. SIDS babies were even lighter, 193 g, and had 3.8 days shorter mean gestational age, compared with same birth-order babies in non-affected sibships. After adjustment for gestational age, the birthweight difference changed only slightly for SIDS siblings, while the difference for SIDS infants was reduced from 193 to 110 g. Further adjustment for smoking reduced the birthweight difference for SIDS siblings, from 74 to 50 g, and SIDS infants, from 110 to 82 g. Intrauterine growth retardation of sibships with a SIDS baby is explained only partly by maternal smoking. The even lower birthweight of the SIDS baby, resulting from shorter gestational age, cannot be explained by smoking, suggesting pregnancy factors specific to the SIDS baby and not to its siblings.     

Ethnic differences in infant-rearing practices and their possible relationship to the incidence of sudden infant death syndrome (SIDS)

Summary. The aetiology of sudden infant death syndrome (SIDS) is still uncertain, although associations with overheating and the prone sleeping position have been reported. In the UK, the incidence of SIDS is considerably lower in infants of Asian origin, but as yet no explanation for this has been suggested. We have studied a group of 202 white and 172 Asian multiparous mothers attending an antenatal clinic to compare the sleeping position and home environment of infants in each ethnic group. We found that significantly more white infants (31%) than Asians (11%) were placed in the prone position at night and that 94% of Asian infants slept in their parents' bedroom, compared with 61% of whites. These observations demonstrate marked differences in the infant rearing practices favoured by Asians and whites and lend support to the concept that the prone position and separate bedrooms may be contributors to the development of sudden infant death.     

Effect of “This Side Up” T-shirts on Infant Sleep Position

Objectives: To assess the impact of “This Side Up” T-shirts on parental practices in Nebraska. Methods: A random sample of 3,210 Nebraska women who gave birth in 2004, stratified by race/ethnicity, was mailed a brief questionnaire on their receipt of a T-shirt and SIDS risk reduction materials at their birthing hospital, and on infant sleep position. Results: Response rates were low (25.9%), ranging from 10.6% for Native American mothers to 46.4% for White mothers. Half (52.0%) had received a T-shirt and 71.6% had received SIDS information. Two-thirds (64.0%) reported that their infants slept on their backs; African-American and Hispanic infants were significantly less likely to back sleep. In univariate logistic regression models, African-American race, Hispanic ethnicity and maternal age 30–39 were significant negative predictors of back sleeping; White race and having received a SIDS brochure were positive predictors. In the fully controlled model African American and Asian race and Hispanic ethnicity were negative predictors of back sleeping; neither receiving SIDS information nor the infant T-shirt was significant. Effects of maternal age and a SIDS informational brochure appeared in models stratified by race/ethnicity. Conclusions: In these data, receiving an infant T-shirt was not related to how mothers placed their infants to sleep. Additional research is needed on effective methods of delivering targeted counseling and promoting safe sleep practices among families, particularly among racial and ethnic subgroups.     

Maternal pre-eclampsia/eclampsia and the risk of sudden infant death syndrome in offspring

To determine whether maternal exposure to pre-eclampsia/eclampsia during pregnancy increases the risk of sudden infant death syndrome (SIDS) in offspring, we conducted a population-based case-control study using the California linked birth and death certificate data. All infants who died of SIDS (ICD-9 code 798.0) during 1989-91 were identified as cases. More than 96% of the identified SIDS cases were diagnosed through autopsy. Ten controls who did not die from SIDS were randomly selected for each case from the birth certificate matched to the case on the year of birth. Among 2,029 cases and 21,037 controls included in the final analysis, mothers of 49 cases (2.4%) and 406 controls (1.9%) had a diagnosis of either pre-eclampsia or eclampsia noted on the birth certificate. After adjustment for maternal age, prenatal smoking, race/ethnicity, parity, maternal education, gestational age at the initial visit for prenatal care, infant year of birth and infant sex, maternal pre-eclampsia/ eclampsia during pregnancy was associated with a 50% increased risk of SIDS in the offspring (odds ratio = 1.5, 95% confidence interval 1.1, 2.0). Potential under-reporting of pre-eclampsia/eclampsia on the birth certificates was likely to be non-differential and is unlikely to explain the finding. Fetal hypoxia resulting from pre-eclampsia/ eclampsia or immunological aetiology affecting the risk of both pre-eclampsia/eclampsia and SIDS may explain the finding.     

Ethnic differences in the incidence of the sudden infant death syndrome (SIDS) in Victoria, Australia 1985–1989

Summary. In order to describe ethnic differences in the incidence of the sudden infant death syndrome (SIDS) records of all livebirths in the State of Victoria, Australia, 1985–1989, excluding those who died in the first month of life, were linked to death certificates. Cases were defined as infants dying with a diagnosis of SIDS between 1 month and 1 year of age ( n = 601) from the cohort of 308052 neonatal survivors. Ethnicity was defined by the mother's country of birth. The SIDS incidence was 2.04/1000 in infants of Australian-born mothers. The relative risk of SIDS was 0.28 (95% confidence interval (CI) 0.15,0.55) in infants whose mothers had been born in Southern Europe and 0.48 (95% CI 0.29, 0.78) in infants whose mothers had been born in Asia. SIDS in infants of Australian-born mothers was associated with low maternal age, high parity, marital status other than married, male sex, multiple birth, low birthweight and preterm birth. After adjustment for those factors in a case-control analysis using a logistic regression model the adjusted odds ratio for SIDS was 0.34 (95% CI 0.17, 0.69) comparing infants whose mothers were born in Southern Europe with infants of Australian-born mothers, and 0.60 (95% CI 0.35, 1.04) for infants whose mothers were born in Asia, compared with infants of the Australian-born. Thus there are substantial ethnic differences in SIDS which are not explained by the classic social and perinatal risk factors.     

Infant care practices related to sudden infant death syndrome in South Asian and White British families in the UK

In the UK, infants of South Asian parents have a lower rate of sudden infant death syndrome (SIDS) than White British infants. Infant care and life style behaviours are strongly associated with SIDS risk. This paper describes and explores variability in infant care between White British and South Asian families (of Bangladeshi, Indian or Pakistani origin) in Bradford, UK (the vast majority of which were Pakistani) and identifies areas for targeted SIDS intervention. A cross-sectional telephone interview study was conducted involving 2560 families with 2- to 4-month-old singleton infants enrolled in the Born in Bradford cohort study. Outcome measures were prevalence of self-reported practices in infant sleeping environment, sharing sleep surfaces, breast feeding, use of dummy or pacifier, and life style behaviours. We found that, compared with White British infants, Pakistani infants were more likely to: sleep in an adult bed (OR = 8.48 [95% CI 2.92, 24.63]); be positioned on their side for sleep (OR = 4.42 [2.85, 6.86]); have a pillow in their sleep environment (OR = 9.85 [6.39, 15.19]); sleep under a duvet (OR = 3.24 [2.39, 4.40]); be swaddled for sleep (OR = 1.49 [1.13, 1.97]); ever bed-share (OR = 2.13 [1.59, 2.86]); regularly bed-share (OR = 3.57 [2.23, 5.72]); ever been breast-fed (OR = 2.00 [1.58, 2.53]); and breast-fed for 8+ weeks (OR = 1.65 [1.31, 2.07]). Additionally, Pakistani infants were less likely to: sleep in a room alone (OR = 0.05 [0.03, 0.09]); use feet-to-foot position (OR = 0.36 [0.26, 0.50]); sleep with a soft toy (OR = 0.52 [0.40, 0.68]); use an infant sleeping bag (OR = 0.20 [0.16, 0.26]); ever sofa-share (OR = 0.22 [0.15, 0.34]); be receiving solid foods (OR = 0.22 [0.17, 0.30]); or use a dummy at night (OR = 0.40 [0.33, 0.50]). Pakistani infants were also less likely to be exposed to maternal smoking (OR = 0.07 [0.04, 0.12]) and to alcohol consumption by either parent. No difference was found in the prevalence of prone sleeping (OR = 1.04 [0.53, 2.01]). Night-time infant care therefore differed significantly between South Asian and White British families. South Asian infant care practices were more likely to protect infants from the most important SIDS risks such as smoking, alcohol consumption, sofa-sharing and solitary sleep. These differences may explain the lower rate of SIDS in this population.     

Tradition and change in the Northern Alberta Woodlands Cree: implications for infant feeding practices

Using anthropological, ethnographic methods of participant observation and interactive, unstructured interviews, we compared traditional and present-day infant feeding practices of the Northern Alberta Woodland Cree. Twelve elderly multigravidae who used traditional ways of childbearing and rearing and 12 women who used present-day practices served as informants. The major change in childbearing was the removal of childbirth from the household to the hospital. This has resulted in the loss of social support and doulas for mothers, who feel insecure and afraid at this time. Infant feeding methods have changed from breastfeeding to the widespread use of canned milk and, if present-day infants are breastfed, it is only for a short time. Both the traditional and present-day mothers introduced solid foods relatively early, but the traditional mothers premasticated the infants' food rather than using commercial baby food or a blender. Following the traditional practices, mothers felt it was important to keep the breasts warm when lactating, and they were reluctant to feed the infant colostrum immediately after delivery. The importance of understanding the cultural context of infant feeding practices is discussed.     

Infant temperament characteristics related to sudden infant death syndrome and its risk factors

Three major components have been repeatedly implicated for the origin(s) of sudden infant death syndrome (SIDS): system, minor sickness and surroundings. All these factors also frame infant temperament, and therefore it seems logical to suppose that the babies who either succumb to or are at risk of SIDS may present with certain behavioural features. The infants who have died of SIDS moved less when lying awake in the crib, during feeding and during nail cutting; less often turned their head away and looked for their mother when held by a new person; were more frequently reported to show an extreme response (either almost never protested or almost always objected) when approached by someone other than main caregiver; and exhibited extreme behavioural patterns when the infant's vocalising on waking up was studied. The infants who died of SIDS had lower activity scores. An unfavourable microenvironment can increase the risk of SIDS, and the babies facing less developmental stimulation had a more negative mood and were less distractible; less organised infants presented with a more negative mood, less distractible behaviour, lower rhythmicity, lower persistence and lower adaptability. The infants born to smoking mothers who are at risk of SIDS had more intensive reactions. The low-birth-weight infants who are at high risk of SIDS were more withdrawing and less adaptable. Infant-parent(s) bed sharing may increase the risk of SIDS, and solitary sleeping infants had a more positive mood and were more persistent. Use of a pacifier may be protective against SIDS, and pacifier users presented with higher rhythmicity. Prone sleep is known to increase the risk of SIDS, and the lowest persistence was a feature of those babies who were usually put to sleep supine and found prone. Infants who snored and/or had noisy breathing in sleep were characterised by more negative mood. Infants with signs of repetitive regurgitation were less distractible.