Article Text
Abstract
Lifting and high psychosocial strain at work has both been associated with adverse birth outcomes, but no studies have investigated the consequences for pregnancy, when they co-occur. Hence, we aimed to investigate the combined effect of lifting and psychosocial strain at work on pregnancy and foetal growth, using the Danish National Birth Cohort (children born 1996-2002). Women were included if pregnant with singletons at gestational age (GA) 22 and worked ≥30 hours/week (N=47,582). Work exposures were extracted from an interview at GA 16 (±3.0). We applied a continuous lifting variable from four questions about heavy and medium lifting, and a psychosocial strain variable, from two questions about demand and influence combined into the four categories of the Demand-Control Model. Pregnancy outcomes were available from the Danish Medical Birth Register: Preterm birth (week 22-36); term birth (week 37-44) but small for GA; term birth but large for GA; and term birth with normal weight (reference group). The overall adjusted multinomial logistic regression analysis showed significant interaction between lifting and job strain with respect to the four outcomes all together (p=0.007). Stratified analyses on the psychosocial exposure showed women in the high strain group had an increased risk of preterm birth (OR=1.04; 95%-CI 1.01-1.06) and having a child large for GA (OR=1.04; 95%-CI 1.01-1.06) for each additional 50 kg lifted. For women in the low strain, passive and active groups, lifting was not associated with the outcomes. Co-occurrence of high strain and lifting seems to increase the risk of adverse birth outcomes.