Objective: To assess childhood cancer risk among children conceived following the use of ovulation-stimulating drugs.
Design: Record linkage study.
Setting: Infertility patients and their offspring as identified through medical records.
Patient(s): Cohort of 30,364 Danish women evaluated for infertility beginning in the early 1960s.
Main outcome measure(s): Standardized incidence ratios (SIRs) compared cancer incidence in the children to the Danish population. Case-cohort techniques calculated rate ratios (RRs) according to prior maternal drug exposures.
Result(s): A total of 51 cancers were identified among the study children, resulting in an SIR of 1.14 (95% confidence interval [CI] 0.8-1.5). Usage of any fertility drug was associated with an RR of 0.82 (95% CI 0.4-1.6) and clomiphene citrate with an RR of 0.77 (95% CI 0.4-1.6). Tumors occurring early in life and nonhematopoietic malignancies (including neuroblastomas) were not associated with drug usage. Nonsignificant elevations in the risk of cancers occurring later in life, especially childhood hematopoietic malignancies (RR for use of any ovulation-stimulating drugs of 2.30, 95% CI 0.8-6.6), may have been related to underlying reasons for medication usage.
Conclusion(s): Although the findings of this study are reassuring, additional adequately powered studies should continue monitoring the effects of ovulation-stimulating drugs on specific tumors, including hematopoietic malignancies.