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Affects the Effectiveness

Genetic variants may make hormonal birth control less effective among some women, Wired reports.

Researchers from the University of Colorado Anschutz Medical Campus enrolled 350 women with implanted hormonal birth control into their study through which they measured their serum etonogestrel concentrations and genotyped at 14 genes linked to steroid hormone function, metabolism, or regulation. As they report in the journal Obstetrics & Gynecology, the researchers uncovered a link between three genetic variants and serum etonogestrel concentrations.

One variant in particular, CYP3A7*1C, which had an allele frequency of about 5 percent, caught their attention, as it leads to the expression of fetal CYP3A7 proteins in adults, boosting etonogestrel metabolism. This, the researchers note, could affect how well hormonal birth control works.

"The biggest takeaway is that we've assumed for so long that if a woman taking birth control gets pregnant, then she must have done something wrong," first author Aaron Lazorwitz tells Wired. "Instead, maybe we need to pay more attention as physicians to other things that might be going on, like genetics, so we can give better, more individualized treatment to women."