Unemployment at municipality level is associated with an increased risk of small for gestational age births – a multilevel analysis of all singleton births during 2005–2010 in Finland

INTRODUCTION: Neighbourhood level deprivation has been shown to influence adverse perinatal outcomes independent of individual level socioeconomic status (SES) in countries with high income inequality, such as the United States. The present study evaluates whether municipality level deprivation defined based on education (proportion of inhabitants with university level education), income (mean income per capita) and unemployment were associated with the prevalence of preterm birth (<37 weeks) and small for gestational age (SGA, birth weight <2 standard deviations) after adjustment for individual level socio-demographics (age, parity, prior preterm births, smoking during pregnancy and SES defined based on maternal occupation at birth) in Finland. METHODS: The study design was cross-sectional. The data gathered from the Medical Birth Register included all singleton births (n = 345,952) in 2005–2010. We fitted Generalized Estimating Equations (GEE) models to account for correlation of preterm birth and SGA clustering within municipality. RESULTS: Of all the women with singleton pregnancies, 4.5% (n = 15,615) gave birth preterm and 3.8% (n = 13,111) of their newborns were classified as SGA. Individual level SES and smoking were important risk factors for each outcome in adjusted models. Controlling for individual level factors, women living in intermediate and high unemployment class municipalities were 6.0% (adjusted odds ratio (aOR) = 1.06; 95% confidence interval (CI) 1.01-1.12) and 13.0% (aOR = 1.13; 95% CI 1.06-1.20), respectively, more likely to give birth to an SGA newborn than women living in low unemployment class municipalities. CONCLUSIONS: After adjustment for individual level socio-demographics, the prevalence of SGA was around 6-13% higher in municipalities with an intermediate or high unemployment rate than municipalities with the lowest unemployment rate. The results suggested that the unemployment rate has an important public health effect with clinical implications since SGA is associated with a higher risk of adverse long-term health outcomes.