Use of multiple linear regression and logistic regression models to investigate changes in birthweight for term singleton infants in Scotland.

AIM: To illustrate the use of regression and logistic regression models to investigate changes over time in size of babies particularly in relation to social deprivation, age of the mother and smoking. BACKGROUND: Mean birthweight has been found to be increasing in many countries in recent years, but there are still a group of babies who are born with low birthweights. DESIGN: Population-based retrospective cohort study. METHOD: Multiple linear regression and logistic regression models are used to analyse data on term 'singleton births' from Scottish hospitals between 1994-2003. RESULTS: Mothers who smoke are shown to give birth to lighter babies on average, a difference of approximately 0.57 Standard deviations lower (95% confidence interval. 0.55-0.58) when adjusted for sex and parity. These mothers are also more likely to have babies that are low birthweight (odds ratio 3.46, 95% confidence interval 3.30-3.63) compared with non-smokers. Low birthweight is 30% more likely where the mother lives in the most deprived areas compared with the least deprived, (odds ratio 1.30, 95% confidence interval 1.21-1.40). CONCLUSIONS: Smoking during pregnancy is shown to have a detrimental effect on the size of infants at birth. This effect explains some, though not all, of the observed socioeconomic birthweight. It also explains much of the observed birthweight differences by the age of the mother. RELEVANCE TO CLINICAL PRACTICE: Identifying mothers at greater risk of having a low birthweight baby as important implications for the care and advice this group receives.

Socio-economic inequalities in cerebral palsy prevalence in the United Kingdom: a register-based study.

Evidence is unclear as to whether there is a socio-economic gradient in cerebral palsy (CP) prevalence beyond what would be expected from the socio-economic gradient for low birthweight, a strong risk factor for CP. We conducted a population-based study in five regions of the UK with CP registers, to investigate the relationship between CP prevalence and socio-economic deprivation, and how it varies by region, by birthweight and by severity and type of CP. The total study population was 1 657 569 livebirths, born between 1984 and 1997. Wards of residence were classified into five quintiles according to a census-based deprivation index, from Q1 (least deprived) to Q5 (most deprived). Socio-economic gradients were modelled by Poisson regression, and region-specific estimates combined by meta-analysis. The prevalence of postneonatally acquired CP was 0.14 per 1000 livebirths overall. The mean deprivation gradient, expressed as the relative risk in the most deprived vs. the least deprived quintile, was 1.86 (95% confidence interval [95% CI 1.19, 2.88]). The prevalence of non-acquired CP was 2.22 per 1000 livebirths. For non-acquired CP the gradient was 1.16 [95% CI 1.00, 1.35]. Evidence for a socio-economic gradient was strongest for spastic bilateral cases (1.32 [95% CI 1.09, 1.59]) and cases with severe intellectual impairment (1.59 [95% CI 1.06, 2.39]). There was evidence for differences in gradient between regions. The gradient of risk of CP among normal birthweight births was not statistically significant overall (1.21 [95% CI 0.95, 1.54]), but was significant in two regions. There was non-significant evidence of a reduction in gradients over time. The reduction of the higher rates of postneonatally acquired CP in the more socioeconomically deprived areas is a clear goal for prevention. While we found evidence for a socio-economic gradient for non-acquired CP of antenatal or perinatal origin, the picture was not consistent across regions, and there was some evidence of a decline in inequalities over time. The steeper gradients in some regions for normal birthweight cases and cases with severe intellectual impairment require further investigation.

Serum thyroid-stimulating hormone concentration and morbidity from cardiovascular disease and fractures in patients on long-term thyroxine therapy.

CONTEXT: For patients on T(4) replacement, the dose is guided by serum TSH concentrations, but some patients request higher doses due to adverse symptoms. OBJECTIVE: The aim of the study was to determine the safety of patients having a low but not suppressed serum TSH when receiving long-term T(4) replacement. DESIGN: We conducted an observational cohort study, using data linkage from regional datasets between 1993 and 2001. SETTING: A population-based study of all patients in Tayside, Scotland, was performed. PATIENTS: All patients taking T(4) replacement therapy (n = 17,684) were included. MAIN OUTCOME MEASURES: Fatal and nonfatal endpoints were considered for cardiovascular disease, dysrhythmias, and fractures. Patients were categorized as having a suppressed TSH (4.0 mU/liter). RESULTS: Cardiovascular disease, dysrhythmias, and fractures were increased in patients with a high TSH: adjusted hazards ratio, 1.95 (1.73-2.21), 1.80 (1.33-2.44), and 1.83 (1.41-2.37), respectively; and patients with a suppressed TSH: 1.37 (1.17-1.60), 1.6 (1.10-2.33), and 2.02 (1.55-2.62), respectively, when compared to patients with a TSH in the laboratory reference range. Patients with a low TSH did not have an increased risk of any of these outcomes [hazards ratio: 1.1 (0.99-1.123), 1.13 (0.88-1.47), and 1.13 (0.92-1.39), respectively]. CONCLUSIONS: Patients with a high or suppressed TSH had an increased risk of cardiovascular disease, dysrhythmias, and fractures, but patients with a low but unsuppressed TSH did not. It may be safe for patients treated with T(4) to have a low but not suppressed serum TSH concentration.

Contribution of smoking during pregnancy to inequalities in stillbirth and infant death in Scotland 1994-2003: retrospective population based study using hospital maternity records.

OBJECTIVE: To quantify the contribution of smoking during pregnancy to social inequalities in stillbirth and infant death. DESIGN: Population based retrospective cohort study. SETTING: Scottish hospitals between 1994 and 2003. PARTICIPANTS: Records of 529 317 singleton live births and 2699 stillbirths delivered at 24-44 weeks' gestation in Scotland from 1994 to 2003. MAIN OUTCOME MEASURES: Rates of stillbirth and infant, neonatal, and post-neonatal death for each deprivation category (fifths of postcode sector Carstairs-Morris scores); contribution of smoking during pregnancy ("no," "yes," or "not known") in explaining social inequalities in these outcomes. RESULTS: The stillbirth rate increased from 3.8 per 1000 in the least deprived group to 5.9 per 1000 in the most deprived group. For infant deaths, the rate increased from 3.2 per 1000 in the least deprived group to 5.4 per 1000 in the most deprived group. Stillbirths were 56% more likely (odds ratio 1.56, 95% confidence interval 1.38 to 1.77) and infant deaths were 72% more likely (1.72, 1.50 to 1.97) in the most deprived compared with the least deprived category. Smoking during pregnancy accounted for 38% of the inequality in stillbirths and 31% of the inequality in infant deaths. CONCLUSIONS: Both tackling smoking during pregnancy and reducing infants' exposure to tobacco smoke in the postnatal environment may help to reduce stillbirths and infant deaths overall and to reduce the socioeconomic inequalities in stillbirths and infant deaths perhaps by as much as 30-40%. However, action on smoking on its own is unlikely to be sufficient and other measures to improve the social circumstances, social support, and health of mothers and infants are needed.

A comparison of customized and population-based birth-weight standards: the influence of gestational age.

OBJECTIVES: We examined how customized birth-weight standards compare to population birth-weight references at term (> or =37 weeks), nearly term (34-36 weeks), moderately preterm (32-33 weeks) and for the very preterm births (28-31 weeks), with respect to perinatal mortality. STUDY DESIGN: Data from the national Swedish Medical Births Register for the years 1992-2001, consisting of a total of 783,303 singletons born at or after 28 completed gestational weeks. Infants were classified as small for gestational age (SGA, <10th centile) according to a conventional population based birth-weight reference and a customized standard. Risk ratios (RR) for still birth and neonatal death were compared between standards by prematurity of the birth. Diagnostic performance measures of specificity, sensitivity and positive and negative predictive values were also evaluated. RESULTS: More than half, 59% (209), of the 355 infants still-born between 28 and 31 weeks gestation were classified as SGA by the customized standard, but only 23% (80), were so classified as SGA by the population reference. However, only 14% (95%CI 13-16) of the 1461 very preterm infants classified as SGA by the customized standard were still-born, compared to 23% (95%CI 19-28) of the 348 infants classified as SGA by the population reference. Therefore, the relative risk of still birth for those classified as SGA by the customized standard is lower, 2.02 (95%CI: 1.65, 2.46), than for the population reference 2.64 (95%CI: 2.11, 3.30). Similar results were observed for the risk of neonatal death. For term weeks, customized standards showed stronger relationships than population references (RR: 4.30 (95%CI 3.82, 4.84) vs. 4.00 (95%CI 3.55, 4.51) for still births). CONCLUSIONS: Customized standards categorize a higher absolute number of preterm infants who are still-born as SGA. However, infants classified as SGA by population references are at higher risk of perinatal mortality than infants classified as SGA by customized standards.

Centile charts for birthweight for gestational age for Scottish singleton births.

BACKGROUND: Centile charts of birthweight for gestational age are used to identify low birthweight babies. The charts currently used in Scotland are based on data from the 1970s and require updating given changes in birthweight and in the measurement of gestational age since then. METHODS: Routinely collected data of 100,133 singleton births occurring in Scotland from 1998-2003 were used to construct new centile charts using the LMS method. RESULTS: Centile charts for birthweight for sex and parity groupings were constructed for singleton birth and compared to existing charts used in Scottish hospitals. CONCLUSION: Mean birthweight has been shown to have increased over recent decades. The differences shown between the new and currently used centiles confirm the need for more up-to-date centiles for birthweight for gestational age.

UKCP: a collaborative network of cerebral palsy registers in the United Kingdom.

Cerebral palsy (CP) is a relatively rare condition with enormous social and financial impact. Information about CP is not routinely collected in the United Kingdom. We have pooled non-identifiable data from the five currently active UK CP registers to form the UKCP database: birth years 1960-1997. This article describes the rationale behind this collaboration and the creation of the database. Data about 6910 children with CP are currently held. The mean annual prevalence rate was 2.1 [corrected] per 1000 live births for birth years 1986-1996. Where type is known, 91 per cent have spastic CP. Where data are available, nearly one-third of children have severely impaired lower limb function, and nearly a quarter have severely impaired upper limb function. As well as describing the range and complexity of motor and associated impairments, the pooled data from the UKCP database provide a platform for studies of aetiology, long-term outcomes, participation and service needs. The UKCP database is an important national resource for the surveillance of CP and the study of its epidemiology in the United Kingdom.