P–374 Investigating causality of risk factors for miscarriage – a Mendelian randomization analysis

Abstract Study question Do modifiable risk factors such as smoking, alcohol or coffee consumption, and adiposity causally increase the risk of sporadic or recurrent miscarriage? Summary answer We found evidence for a causal relationship between smoking initiation and sporadic miscarriage, but not for any other risk factor tested. What is known already Miscarriage is estimated to end between 10–25% of clinically confirmed pregnancies, and many observational studies have suggested numerous lifestyle factors, such as coffee and alcohol consumption, smoking and increased adiposity, may increase miscarriage risk. However, results are not always consistent across studies, and definitive causal relationships between various risk factors and miscarriage have not yet been demonstrated. Mendelian randomization utilizes genetic variants significantly associated with heritable risk factors (i.e. at P-values