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To date, several studies have investigated the intergenerational effect of preterm and small-for-gestational-age (SGA) births. However, most studies excluded both twin mothers and twin offspring from the analyses. Thus, the objective of this study was to investigate the intergenerational effect of preterm birth and SGA births among twins and singletons. A prospective population-based register study of mother–firstborn offspring pairs recorded in the Swedish Medical Birth Register was performed. The study included 4,073 twins and 264,794 singletons born from 1973–1983 and their firstborns born from 1986–2009. Preterm birth was defined as birth at <37 weeks of gestation, and SGA as birth weight <2 standard deviations of the Swedish standard. Logistic regressions were performed to estimate the intergenerational effect of each birth characteristic. Adjustments were made for maternal grandmothers’ and mothers’ socio-demographic factors, in addition to maternal birth characteristics. Among mothers born as singletons, being born preterm was associated with an increased risk of delivering a preterm child (adjusted odds ratio (OR) 1.39, 95% Confidence Interval (CI) = 1.29–1.50), while being born SGA increased the likelihood of having an SGA child (adjusted OR 3.04, 95% CI = 2.80–3.30) as well as a preterm child (adjusted OR 1.30, 95% CI = 1.20–1.40). In twin mothers, the corresponding ORs tended to be lower, and the only statistically significant association was between an SGA mother and an SGA child (adjusted OR 2.15, 95% CI = 1.40–3.31). A statistically significant interaction between twinning and mother's size for gestational age was identified in a multivariate linear regression analysis, indicating that singleton mothers born SGA were associated with a lower birth weight compared with mothers not born SGA. Preterm birth and SGA appear to be transferred from one generation to the next, although not always reaching statistical significance. These effects seem to be less evident in mothers born as twins compared with those born as singletons. [ABSTRACT FROM PUBLISHER]

BackgroundRisk for drug abuse (DA) is strongly associated with neighborhood social deprivation (SD). However, the causal nature of this relationship is unclear.MethodThree Swedish population-based cohorts were followed up over 5 years for incident registration of DA in medical, legal or pharmacy records. In each cohort, we examined the SD–DA association, controlling carefully for individual socio-economic status (SES) with multiple measures, in the entire sample and among pairs of first cousins, paternal and maternal half-siblings, full siblings and monozygotic (MZ) twins discordant for SD exposure. The number of informative relative pairs ranged from 6366 to 166 208.ResultsIn all cohorts, SD was prospectively related to risk for incident DA. In relative pairs discordant for SD exposure, the SD–DA association was similar to that seen in the entire population in cousins, half-siblings, full siblings and MZ twins. Eliminating subjects who were residentially unstable or had DA in the first two follow-up years did not alter this pattern. When divided by age, in the youngest groups, the SD–DA association was weaker in siblings than in the entire population.ConclusionsAcross three cohorts, controlling for individual SES and confounding familial factors, SD prospectively predicted risk for incident DA registration. These results support the hypothesis that the SD–DA association is in part causal and unlikely to result entirely from personal attributes, which both increase risk for DA and cause selection into high SD environments. At least part of the SD–DA association arises because exposure to SD causes an increased risk of DA. [ABSTRACT FROM AUTHOR]