Recent research results suggest that becoming pregnant even while being on birth control may be due to genes. Dr. Aaron Lazorwitz’s research team at University of Colorado Anschutz Medical School's Department of Obstetrics and Gynecology showed that females containing a particular gene mutation may not respond to birth control plans. The research team stated that females with CYP3A7*1C gene mutation have small or no effect from birth control. This mutation results in rapid degradation of estrogen and progesterone, which normally function to suppress pregnancy. So taking birth control pills may not prevent pregnancy. Particularly, using low-dose birth control pills for females with this mutation are at risk of becoming pregnant if sexually active.

The CYP3A7 gene is expressed to produce CYP3A7 protein in the fetus, but the expression is normally soon turned off; however, female fetus containing the mutant gene continue its expression. This research study monitored 350 females who are on etonogestrel implant, which is a low-dose birth control method. Of these individuals, 5% carried the CYP3A7*1C mutation, 28% of which had lower than the target female sex hormone level of 90 pg/mL. Females especially with high BMI and longer use history of the implant birth control had lower hormone levels. Females with this genetic mutation and who are on low-dose birth control methods may not be having good birth control effects. This research study was published on March 12, 2019 in Obstetrics & Gynecology, a College of Obstetricians and Gynecologists Journal.

References:
Obstet Gynecol. 2019 Mar 11.
(https://journals.lww.com/greenjournal/Abstract/publishahead/Influence_of_Genetic_Variants_on_Steady_State.97768.aspx)