Maternal occupational physical activity during pregnancy and childhood cancers in Denmark 1968-2013.

OBJECTIVE

To examine associations between maternal occupational physical activity (OPA) during pregnancy and childhood cancer risk in offspring.

METHODS

The study population included all cancer cases born in Denmark between 1968 and 2013, aged 0–19 at diagnosis between 1968 and 2016 (N = 7077). Sex- and birth-year matched controls (ratio 1:25) were randomly selected from the Central population registry. maternal OPA was assessed by a job exposure matrix based on the nordic occupational cancer study (score: heavy or rather heavy physical work versus all other levels). Unconditional logistic regression adjusted for potential confounders was used to estimate effects. Dose-response relationships examined by OPA exposure probability groups (high, medium, low versus no exposure).

RESULTS

Medium cumulative maternal OPA exposure was associated with an average 8% increased childhood cancer risk for all cancers combined. Medium and high intensity OPA during pregnancy were positively associated with medulloblastoma (adjusted odds ratio (OR) = 1.53, 95% confidence interval (CI) 1.01–2.31 and OR = 2.01, 95% CI 1.20–3.37, respectively). Various measures of OPA were most consistently associated with increased risks of medulloblastoma. Among healthcare professionals, high OPA also increased melanoma risk in offspring (OR = 1.48, 95% CI 1.00-2.19).

CONCLUSIONS

Higher levels of maternal OPA are associated with increased risks of medulloblastoma, and possibly melanoma in the offspring. If associations are corroborated, regulations should be considered to protect women of child-bearing age from being exposed to high levels of physical activity at work.