Exposure to systemic antibacterial medications during pregnancy and risk of childhood cancer.

BACKGROUND: Up to one-third of women receive prescriptions for systemic antibacterial medications during pregnancy. This paper looks at the association between maternal use of systemic antibacterial medications during pregnancy and childhood cancer risk in the offspring using the prospective data on medication.

METHODS: A population-based follow-up study was carried out using Danish and Swedish register data. Exposure was maternal redemption of a prescription for a systemic antibacterial in the 3 months prior to pregnancy and during pregnancy (exposure window) documented in the national prescription registers, and offspring were followed up from birth to a cancer diagnosis, death, emigration, day before 15th birthday or end of follow-up, whichever came first. Timing, dosage, specific medication types and types of childhood cancer were also considered.

RESULTS: Mothers of 35.1% (n = 506,194) of the children filled at least one prescription for systemic antibacterials during the exposure window. Exposed children had a hazard ratio of 1.08 (95% confidence interval: 0.97, 1.20) compared with unexposed children. Statistically significant results were found for some specific medications (for example, 'other antibacterials'/Anatomical Therapeutic Chemical code J01X) and combinations of cancer types and specific medications (leukaemia and other antibacterials, and hepatic cancers and tetracyclines).

CONCLUSIONS: The results of this study indicate that most antibacterial drugs used during pregnancy were not related to childhood cancer risk in the offspring. However, some may be associated with the development of some specific types of childhood cancers. Our findings need to be replicated in an independent data source.