Cliona McGarvey

Factors relating to the infant’s last sleep environment in sudden infant death syndrome in the Republic of Ireland

Aim: To identify risk factors for sudden infant death syndrome (SIDS) in the sleeping environment of Irish infants. Methods: A five year population based case-control study with parental interviews conducted for each case and three controls matched for age, place of birth, and last sleep period. A total of 203 SIDS cases and 622 control infants born 1994–98 were studied. Results: In a multivariate analysis, co-sleeping significantly increased the risk of SIDS both as a usual practice (adjusted OR 4.31; 95% CI 1.07 to 17.37) and during the last sleep period (adjusted OR 16.47; 95% CI 3.73 to 72.75). The associated risk was dependent on maternal smoking (OR 21.84; 95% CI 2.27 to 209.89), and was not significant for infants who were ⩾20 weeks of age (OR 2.63; 95% CI 0.49 to 70.10) or placed back in their own cot/bed to sleep (OR 1.07; 95% CI 0.21 to 5.41). The use of pillows, duvets, and bedding with tog value ⩾10 were not significant risk factors when adjusted for the effects of confounding variables, including maternal smoking and social disadvantage. However, the prone sleeping position remains a significant SIDS risk factor, and among infants using soothers, the absence of soother use during the last sleep period also significantly increased the SIDS risk (OR 5.83; CI 2.37 to 14.36). Conclusion: Co-sleeping should be avoided in infants who are <20 weeks of age, or whose mothers smoked during pregnancy. The prone position remains a factor in some SIDS deaths, and the relation between soother use and SIDS is a complex variable requiring further study.

An 8 year study of risk factors for SIDS: bed-sharing versus non-bed-sharing

Background: It is unclear if it is safe for babies to bed share with adults. In Ireland 49% of sudden infant death syndrome (SIDS) cases occur when the infant is bed-sharing with an adult. Objective: To evaluate the effect of bed-sharing during the last sleep period on risk factors for SIDS in Irish infants. Design: An 8 year (1994–2001) population based case control study of 287 SIDS cases and 831 controls matched for date, place of birth, and sleep period. Odds ratios and 95% confidence intervals were calculated by conditional logistic regression. Results: The risk associated with bed-sharing was three times greater for infants with low birth weight for gestation (UOR 16.28 v 4.90) and increased fourfold if the combined tog value of clothing and bedding was ⩾10 (UOR 9.68 v 2.34). The unadjusted odds ratio for bed-sharing was 13.87 (95% CI 9.58 to 20.09) for infants whose mothers smoked and 2.09 (95% CI 0.98 to 4.39) for non-smokers. Age of death for bed-sharing and sofa-sharing infants (12.8 and 8.3 weeks, respectively) was less than for infants not sharing a sleep surface (21.0 weeks, p<0.001) and fewer bed-sharing cases were found prone (5% v 32%; p = 0.001). Conclusion: Risk factors for SIDS vary according to the infant’s sleeping environment. The increased risk associated with maternal smoking, high tog value of clothing and bedding, and low z scores of weight for gestation at birth is augmented further by bed-sharing. These factors should be taken into account when considering sleeping arrangements for young infants.

The placenta in infants >36 weeks gestation with neonatal encephalopathy: a case control study

Objective To determine placental characteristics associated with neonatal encephalopathy (NE) and correlate these with short- and long-term neurodevelopmental outcome. Design Case/control study. Setting Neonatal Intensive Care Unit, Rotunda Hospital, Dublin, Ireland. Patients Newborns ≥36 weeks gestation, with NE (cases). Healthy term newborns (controls). Interventions Placental pathology was obtained from the official placental report. Brain MRI was blindly reviewed. Children were assessed using a variety of standardised assessments. Data were analysed using multinomial logistic regression analysis. Main outcome measures RRR for grade of encephalopathy. OR for neurodevelopmental outcome. Results Placental reports were available on 141 cases (76 grade 1; 46 grade 2; 19 grade 3) and 309 control infants. Meconium phagocytosis, haemorrhage, raised placental to birth weight ratio and/or markers of infection/inflammation were independently associated with NE and showed a synergistic effect, when combined, for short- and long-term impairments. Conclusions Evaluation of the mechanisms leading to the placental characteristics identified may help to characterise the causal pathway of NE.

Sudden unexplained death in childhood (1–4 years) in Ireland: an epidemiological profile and comparison with SIDS

Objective To examine the incidence of sudden unexplained death in children 1–4 years old (SUDC) in Ireland and to compare the epidemiological profile of SUDC with that of SIDS. Design All cases of sudden unexplained death in children <5 years in Ireland between 1994 and 2008 were reviewed. Epidemiological information obtained from parental questionnaires and post-mortem reports was examined, and data on cases ≥52 weeks compared with cases <52 weeks. Results SUDC accounted for 5% (n=44) of deaths in children aged 1–4 years during 1994–2008. During this period, the SIDS rate dropped from 0.71 to 0.34 per 1000 live births, while the SUDC rate increased from 0.08 to 0.18 deaths per 10 000 population aged 1–4 years. The median age of SUDC cases was 71.5 weeks, and the male/female ratio was 1.3:1. All died during a sleep period, 71% between 10pm and 8am, and more than two-thirds were found prone. Fewest cases occurred during July–September (11%), and a greater proportion occurred at weekends (55%). 52% (17/33) had symptoms (any) in the 48 h before death, and 35% (11/31) visited their general practitioner because of illness in the week preceding death. SUDC differed from SIDS in prevalence of maternal smoking (38% vs 72%, p<0.001), bed-sharing (17% vs 49%, p<0.001), and whether found prone (72% vs 23%, p<0.001). Conclusion While SUDC shares some characteristics with SIDS, there are also some important differences. Further data collection will help determine whether SIDS and SUDC represent the same pathophysiological entity. Standardisation of protocols for investigating sudden deaths is urgently required for accurate diagnosis of cases.

A multivariate “time based” analysis of SIDS risk factors

Aims: To investigate the influence of analytical design on the variability of published results in studies of sudden infant death syndrome (SIDS). Methods: The results of a prospective case-control study, of 203 cases of SIDS, and 622 control infants are presented. All variables significant on univariate analysis were included in a multivariate model analysed in nine stages, starting with sociodemographic variables, then sequentially and cumulatively adding variables relating to pregnancy history, current pregnancy, birth, the interval from birth to the week prior to death, the last week, the last 48 hours, and the last sleep period. A ninth stage was created by adding placed to sleep prone for the last sleep period. Results: As additional variables are added, previously published SIDS risk factors emerged such as social deprivation, young maternal age, ⩾3 previous live births, maternal smoking and drinking, urinary tract infection in pregnancy, reduced birth weight, and the infant having an illness, regurgitation, being sweaty, or a history of crying/colic in the interval from birth to the week before death, with co-sleeping and the lack of regular soother use important in the last sleep period. As the model progressed through stages 1–9, many significant variables became non-significant (social deprivation, young maternal age, maternal smoking and drinking) and in stage 9 the addition of placed to sleep prone for the last sleep period caused ⩾3 previous live births and a reduced birth weight to become significant. Conclusion: The variables found to be significant in a case-control study, depend on what is included in a multivariate model.

A case-control study of hypoxic-ischemic encephalopathy in newborn infants at >36 weeks gestation.

OBJECTIVE The purpose of this study was to determine risk factors that are associated with hypoxic ischemic encephalopathy (HIE). STUDY DESIGN This was a case-control study that included newborn infants with HIE who were admitted to the hospital between January 2001 and December 2008. Two control newborn infants were chosen for each case. Logistic regression and classification and regression tree (CART) analysis that compared control infants and cases with grade 1 HIE and control infants and cases with grades 2 and 3 HIE was performed. RESULTS Two hundred thirty-seven cases (newborn infants with grade 1 encephalopathy, 155; newborn infants with grade 2 encephalopathy, 61; newborn infants with grade 3 encephalopathy, 21) and 489 control infants were included. Variables that were associated independently with HIE included higher grade meconium, growth restriction, large head circumference, oligohydramnios, male sex, fetal bradycardia, maternal pyrexia and increased uterine contractility. CART analysis ranked high-grade meconium, oligohydramnios, and the presence of obstetric complications as the most discriminating variables and defined distinct risk groups with HIE rates that ranged from 0-86%. CONCLUSION CART analysis provides information to help identify the time at which intervention in labor may be of benefit.

Brain magnetic resonance imaging and outcome after hypoxic ischaemic encephalopathy

Abstract Objective: To correlate pattern of injury on neonatal brain magnetic resonance imaging (MRI) with outcome in infants ≥36 + 0 weeks gestation with hypoxic ischaemic encephalopathy. Methods: Prospective cohort study. Images were blindly reviewed. Children were assessed using a variety of standardised assessments. Results: MRI brain was performed on 88 infants. Follow up was available in 73(83%) infants. Eight of 25(32%) children with normal imaging had below normal assessment scores. Eight infants (12%) had isolated punctate white matter lesions and five of these had abnormal assessment scores. Death and cerebral palsy were seen only in children with imaging scores ≥3 on basal ganglia/thalami (BGT) score or ≥4 on watershed score. No developmental concerns were raised in 3/7(43%) infants with isolated watershed injury. Ten of 13(77%) infants with isolated BGT injury died or developed cerebral palsy. All 23 children with posterior limb of the internal capsule (PLIC) injury displayed developmental difficulties. Conclusions: Almost one-third of infants with a normal MRI brain may be at risk of developmental problems. Punctate foci of white matter injury are common and not always benign. PLIC involvement is usually associated with neurological sequelae including isolated cognitive deficits. Worst outcomes are associated with basal ganglia injury.

Timing of administration of antenatal magnesium sulfate and umbilical cord blood magnesium levels in preterm babies

Abstract Background: The optimum timing of administration of magnesium sulfate (MgSO4) in relation to delivery is not known. The general consensus is to achieve administration to the mother at least 4 hours prior to preterm delivery. Objective: To investigate potential predictors of umbilical cord blood magnesium (Mg) concentrations, in particular, timing of antenatal MgSO4 administration in relation to delivery. Study design: A prospective observational study of infants delivered at less than 32 weeks’ gestational age. Cord bloods samples were collected at delivery and Mg levels analyzed. Results: Of the 81 included cases, five received no antenatal MgSO4, 65 received a 4 g bolus only, and 11 received a 4 g bolus and 1 g/hour infusion. The median time of bolus administration before delivery was 104 minutes (IQR: 57–215). The mean magnesium level was 0.934 mmol/L in the no antenatal MgSO4 group, 1.018 mmol/L in the bolus only group, and 1.225 mmol/L in the bolus and infusion group (p < .05). In the bolus only group, the highest mean magnesium concentration (1.091 mmol/L) was achieved with administration 1–2 hours before delivery, but the difference was small and not statistically significant. On multiple regression analysis, lower birthweight Z scores and gestational age were independently associated with higher cord blood Mg levels. Conclusions: In the bolus only group, the highest mean Mg levels were observed with administration 1–2 hours before delivery, but the findings were not statistically significant. Compared to the rest of the cohort, higher Mg levels were found when a bolus was followed by an infusion. Following a MgSO4 bolus, some growth restricted extremely preterm babies may have higher Mg levels than would be otherwise expected.