An estimated 8 million children were born after the use of assisted reproductive technology (ART) between 1978 and 2018.¹ In Denmark, a country with one of the world’s highest rates of ART,² 9.8% of all children were born after use of fertility treatment in 2018.³

Background: Surveillance of childhood cancer incidence is informative for etiologic research and health policy. However, high-quality data covering several decades of virtually complete cancer diagnosis in children is sparse. Methods: Incident cases of childhood cancer (0–19 years at diagnosis), classified according to Birch and Marsden’s International Classification of Childhood Cancer, first edition (ICCC-1), were identified in the Danish Cancer Registry and used to calculate age-standardized incidence rates (ASRs) and estimated annual percentage change (EAPC) separately for 1943–1977 (early period) and 1977–2014 (recent period). Results: During 1943–2014, 15,184 childhood cancer cases were reported. The ASR for any cancer was 13.0 per 100 000 person-years in the early period (EAPC 0.55%; 95% CI 0.30–0.80) and 17.7 per 100 000 person-years in the recent period (EAPC 1.16%; 95% CI 0.96–1.36). In both periods, the increasing trend was seen in both boys (EAPC 0.69%; 95% CI 0.43–0.96/EAPC 0.96%; 95% CI 0.75–1.17) and girls (EAPC 0.37%; 95% CI −0.01–0.75/EAPC 1.41%; 95% CI 1.11–1.72) and in children aged 0–14 years (EAPC 0.53%; 95% CI 0.26–0.80/EAPC 0.86%; 95% CI 0.64–1.08) and 15–19 years (EAPC 0.60%; 95% CI 0.19–1.02/EAPC 1.97%; 95% CI 1.67–2.28). Increasing trends were observed for all main diagnostic groups. Conclusions: The incidence of childhood cancer in Denmark has increased since the 1940s, especially since 1977 and in older children. In recent years the increase has been most pronounced among girls.

Introduction: The aim of this study was to investigate whether consumption of coffee, tea and caffeine affects the risk of primary infertility in women.Material and methods: We selected nulliparous Danish women aged 20–29 years from a prospective cohort and retrieved information on coffee and tea consumption from a questionnaire and an interview at enrollment. We assessed the women's fertility by linkage to the Danish Infertility Cohort and retrieved information on children and vital status from the Civil Registration System. All 7574 women included for analysis were followed for primary infertility from the date of enrollment (1991–1993) until 31 December 2010. Analyses were performed with Cox proportional hazard models.Results: During follow up, primary infertility was diagnosed in 822 women. Compared with never consumers, the risk of primary infertility among women who drank coffee or tea was not affected. The risk of primary infertility was neither associated with an increasing number of daily servings of coffee (hazard ratio 1.00; 95% confidence interval (CI), 0.97–1.03) or tea (hazard ratio 1.01; 95% CI, 0.99–1.03) in consumers only. Concerning total caffeine consumption (from coffee and tea), the risk of infertility was similar among consumers compared with never consumers. Finally, none of the additional daily 100 mg of caffeine affected the risk among consumers only (hazard ratio 1.00; 95% CI 0.98–1.02).Conclusions: In this population‐based cohort study, not restricted to women seeking pregnancy, we found no association between coffee, tea or total caffeine consumption and the risk of primary infertility in women.

Background: Studies have suggested increased risks of childhood leukaemia after prenatal exposure to antibiotics, particularly nitrofurantoin. However, these findings may be related to the underlying maternal infection. This multinational study aimed to investigate the association between prenatal nitrofurantoin exposure and childhood leukaemia while accounting for maternal infection. Methods: In a population-based cohort study of children born in Denmark, Finland, Norway or Sweden from 1997 to 2013, prenatal exposure to nitrofurantoin or pivmecillinam (active comparator) was ascertained from national Prescription Registries. Childhood leukaemia was identified by linkage to national Cancer Registries. Poisson regression was used to estimate incidence rate ratios (IRRs) and incidence rate differences (IRDs) with inverse probability of treatment weights applied to account for confounding. Results: We included 44 091 children prenatally exposed to nitrofurantoin and 247 306 children prenatally exposed to pivmecillinam. The children were followed for 9.3 years on average (standard deviation 4.1). There were 161 cases of childhood leukaemia. The weighted IRR for prenatal nitrofurantoin exposure when compared with pivmecillinam was 1.34 (95% confidence interval 0.88, 2.06), corresponding to an IRD of 15 per million person-years. Higher point estimates were seen for first- and third-trimester exposure. There was no evidence of a dose–response relationship. Conclusions: Prenatal exposure to nitrofurantoin was not substantially associated with childhood leukaemia, although a slightly elevated IRR with confidence intervals including the null was observed, corresponding to a small absolute risk. The lack of a dose–response relationship and a clear biological mechanism to explain the findings suggests against a causal association.