Objective To identify modifiable risk factors for miscarriage and to estimate the preventable proportion of miscarriages that could be attributed to these.Design Nationwide observational follow-up study.Setting Denmark.Population Ninety-one thousand four hundred and twenty seven pregnancies included in the Danish National Birth Cohort between 1996 and 2002.Methods Information on potentially modifiable risk factors before and during pregnancy was collected by means of computer-assisted telephone interviews and linkage with Danish registers, ensuring almost complete follow-up of pregnancy outcome. Modifiable risk factors for miscarriage were identified by multiple Cox regression analysis, which provided the background for our estimations of population attributable fractions. In all, 88 373 pregnancies had full information on all covariates and were included in this analysis.Main outcome measures Miscarriage before 22 completed weeks of gestation.Results The potentially modifiable pre-pregnant risk factors associated with increased miscarriage risk were: age of 30 years or more at conception, underweight, and obesity. During pregnancy the modifiable risk factors were: alcohol consumption, lifting of >20 kg daily, and night work. We estimated that 25.2% of the miscarriages might be prevented by reduction of all these risk factors to low risk levels. Modification of risk factors acting before and during pregnancy could lead to prevention of 14.7 and 12.5%, respectively, of the miscarriages. Maternal age at conception and alcohol consumption were the most important risk factors.Conclusions Miscarriage risk is increased by multiple potentially modifiable risk factors and a considerable proportion of miscarriages may be preventable.

Homelessness remains a societal problem. Compiled evidence of predictors for becoming homeless and exiting homelessness might be used to inform policy-makers and practitioners in their work to reduce homeless-related problems. We examined individual-level predictors for becoming homeless and exiting homelessness by searching PubMed, EMBASE, PsycINFO, and Web of Science up to January 2018. Becoming homeless and exiting homelessness were the outcomes. Observational studies with comparison groups from high-income countries were included. The Newcastle Ottawa Quality Assessment Scale was used for bias assessment. Random effects models were used to calculate pooled odds ratios (ORs) with 95% confidence intervals (CIs). We included 116 independent studies of risk factors for becoming homeless and 18 for exiting homelessness. We found evidence of adverse life events as risk factors for homelessness, e.g., physical abuse (OR 2.9, 95% CI 1.8-4.4) and foster care experiences (3.7, 1.9-7.3). History of incarceration (3.6, 1.3-10.4), suicide attempt (3.6, 2.1-6.3), and psychiatric problems, especially drug use problems (2.9, 1.5-5.1), were associated with increased risk of homelessness. The heterogeneity was substantial in most analyses (I 2 > 90%). Female sex (1.5, 1.1-1.9; I 2 = 69%) and having a partner (1.7, 1.3-2.1; I 2 = 40%) predicted higher chances whereas relationship problems (0.6, 0.5-0.8), psychotic disorders (0.4, 0.2-0.8; I 2 = 0%), and drug use problems (0.7, 0.6-0.9; I 2 = 0%) reduced the chances for exiting homelessness. In conclusion, sociodemographic factors, adverse life events, criminal behaviour, and psychiatric problems were individual-level predictors for becoming homeless and/or exiting homelessness. Focus on individual-level vulnerabilities and early intervention is needed. PROSPERO registration number: CRD42014013119.

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