medwireNews: The use of hormonal contraceptives just before and during pregnancy may significantly increase the risk for childhood non-lymphoid leukemia, Danish researchers report.
“Since the absolute risk of childhood leukaemia remains low, the increased risk found is not a major health concern,” Marie Hargreave (Danish Cancer Society Research Center, Copenhagen) and co-authors remark.
Nevertheless, they add that their data “suggest an important direction for future research,” because at present “almost no risk factors have been established for [childhood] leukaemia.”
The investigators found that during a median 9.3 years of follow-up 606 (0.05%) of 1,185,157 children born between 1996 and 2014 were diagnosed with leukemia: 465 with lymphoid leukemia and 141 with non-lymphoid leukemia.
The majority (65.7%) of the children studied were born to mothers who had stopped using hormonal contraception more than 3 months prior to pregnancy (previous use), while 11.5% had mothers who had used hormonal contraception within 3 months of pregnancy or during pregnancy (recent use). The remaining 22.8% were born to mothers who had never used hormonal contraceptives.
As reported in The Lancet Oncology, children born to women with recent hormonal contraceptive use had a significant 1.46-fold increased risk for any leukemia compared with children of women who never used hormonal contraception. The risk was a nonsignificant 1.78-fold higher with use during pregnancy and a significant 1.25-fold higher with previous use of hormonal contraceptives.
However, the researchers note that when previous used was stratified into three exposure windows, only use during the 3–6 months prior to pregnancy, and not in the 6–12 months or 12 months and beyond, was associated with an increased risk for any leukemia, compared with no use, at a hazard ratio of 1.38.
When the data were analyzed according to the type of leukemia, there was no significant association between oral contraceptive use at any time and the risk for lymphoid leukemia.
By contrast, recent use was associated with a significant 2.17-fold increased risk for non-lymphoid leukemia compared with no use, while the risk was 3.87-fold higher when hormonal contraceptives were used during pregnancy.
The researchers calculated that the use of hormonal contraceptives close to or during pregnancy may have resulted in approximately one additional case of leukemia per about 47,170 exposed children, or 25 additional cases among Danish children during the 9.3-year study period.
The increased risk “was associated mainly with use of oral combined products containing oestrogen; we found no effect of progestin-only products,” Hargreave et al note.
They conclude: “Although the absolute risk is low, our findings suggest the intrauterine hormonal environment affects leukaemia development in children.”
By Laura Cowen
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