Hargreave M, et al. - Researchers examined the link between maternal use of hormonal contraception and diagnosis of leukemia in their children. According to findings, non-lymphoid leukemia development in children was influenced by the use of hormonal contraception by their mothers.

Methods

• Via follow-up, a nationwide cohort of 1,185,157 liveborn children was examined between 1996 and 2014 listed in the Danish Medical Birth Registry.
• Using the Danish Cancer Registry, children diagnosed with leukemia were identified.
• Researchers used redeemed prescriptions from the Danish National Prescription Registry to obtain information regarding maternal hormonal contraceptive use, categorized as: no use (never used contraception before birth; reference category), previous use (>3 months before start of pregnancy), and recent use (≤3 months before and during pregnancy).
• For maternal hormonal contraceptive use during pregnancy, risk estimates were calculated separately.
• A diagnosis of any leukemia in the children was the primary outcome, and diagnoses of lymphoid leukemia and non-lymphoid leukemia were assessed as secondary outcomes.
• Estimation of hazard ratios (HRs) with 95% CIs for risk of leukemia in children was done by using Cox proportional hazards models.

Results

• A total of 1,185,157 liveborn children accumulated 11,114,290 person-years of follow-up (median 9.3 years, IQR 4.6–14.2) between January 1, 1996 and December 31, 2014, during which leukemia was diagnosed in 606 children (465 with lymphoid leukemia and 141 with non-lymphoid leukemia).
• A higher risk for any leukemia was seen among children born to women with recent use of any type of hormonal contraception vs children of women who never used contraception (HR 1.46, 95% CI 1.09–1.96; p=0.011); 1.78 was the estimated risk for exposure during pregnancy (0.95–3.31; p=0.070).
• Findings demonstrated no link between timing of use and risk for lymphoid leukemia (HR 1.23, 95% CI 0.97–1.57, p=0.089, for previous use and 1.27, 0.90–1.80, p=0.167, for recent use); however, the reported HRs for non-lymphoid leukemia for recent use and for use during pregnancy were 2.17 (1.22–3.87; p=0.008) and 3.87 (1.48–10.15; p=0.006), respectively.
• They also observed that hormonal contraception use close to or during pregnancy might have led to one additional case of leukemia per about 50,000 exposed children, or 25 cases during the 9-year study period.