Birth size, school performance and family social position: a study of 650,000 children.

BACKGROUND: Low birth weight (BW) is associated with lower cognitive functioning, but less is known of these associations across the full range of the BW distribution and its components. We analyzed how BW, birth length (BL) and birth ponderal index (BPI, kg/m3) are associated with school performance and how childhood family social position modifies these associations. METHODS: Medical birth records of all Finnish children born in 1987-1997 were linked to school performance records at 16 years of age (N = 642,425). We used population averaged and within-siblings fixed-effects linear regression models. RESULTS: BL showed a linear and BW a curvilinear association with school performance whereas for BPI the association was weak. The strongest association was found for BL explaining 0.08% of the variation in school performance in boys and 0.14% in girls. Demographic, gestational and social factors partly explained these associations. Similar but weaker associations were found within sibships. The association of BL with school performance was stronger at lower levels of family social position. CONCLUSION: BL shows a linear association with school performance and can explain more school performance variation than BW. At the population level, BL can offer useful information on intrauterine environmental factors relevant for cognitive performance. IMPACT: Birth length is linearly associated with school performance in late adolescence and explains a larger proportion of school performance variation than birth weight. The association between birth length and school performance is stronger in families with lower socio-economic position. At the population level, birth length can offer information on the intrauterine environment relevant for later cognitive performance.

The association of lowered alcohol prices with birth outcomes and abortions: A population-based natural experiment.

BACKGROUND AND AIMS: Alcohol use during pregnancy remains an important risk factor for adverse birth outcomes, but little is known regarding how alcohol prices affect pregnancy outcomes on the population level. We assess the associations between decreased alcohol prices with birth outcomes and abortions. DESIGN: Using national registers, we used interrupted time-series modelling to compare outcomes of pregnancies conceived before and after a tax cut, resulting in 33% mean decrease of off-premise alcohol prices on 1 March 2004. We also addressed possible heterogeneity of the associations by maternal age and household income. SETTING: Finland. PARTICIPANTS: All registered pregnancies starting 2 years before and 1 year after the alcohol price cut (analysis sample consisted of 169 735 live births and 32 441 abortions). MEASUREMENTS: The outcomes were birth weight, gestational age, the probability of low birth weight (< 2500 g at birth), preterm birth (< 37 weeks of gestation), any congenital malformations and share of registered abortions of pregnancies. FINDINGS: On the population level, lowered alcohol prices were associated with an increase in abortions immediately after the price cut [+0.84 percentage points; 95% confidence interval (CI) = 0.2, 1.4]. For birth outcomes, negative associations were observed among women in the lowest income quintile; for example, increased probabilities of low birth weight (+1.5 percentage points; 95% CI = 0.4, 2.6) and preterm birth (+1.98 percentage points; 95% CI = 0.8, 3.2). All changes were strongest immediately after the price cut and attenuated during the course of the following year. CONCLUSIONS: Lowered alcohol prices in Finland were associated with a short-term increase in adverse birth outcomes among low-income mothers and an overall increase in abortions.