Abstract
Objective: To explore the potential factors that contribute to
the occurrence of medical abortion(MA) through a Mendelian
randomization(MR) study. Design: Univariate MR(UVMR) and
multivariate MR(MVMR) analyses. Setting: Genetic variants from
European populations. Population or Sample: Instrumental
variants for MA were obtained from FinnGen with 36,232 cases and 149,622
controls. Methods: The inverse variance weighting method was
adopted as the primary analysis. Main outcome measures: The
associations of MA with household income(HI), education attainment(EA),
cognitive performance(CP), risky behaviors: smoking behavior(SB),
alcohol consumption(AC), and reproductive traits: age at first sexual
intercourse(AFS), lifetime number of sexual partners(LNSP), age at first
birth(AFB), age at last birth(ALB). Results: In the UVMR,
increasing HI, EA, AFS and AFB appeared to reduce MA risk(HI, OR=0.569,
P = 7.93E-08; EA, OR=0.875, P = 6.02E-21; AFS, OR=0.439, P = 5.17E-25;
AFB, OR=0.815, P = 5.46E-12), whereas SB and LNSP appeared to add to MA
risk((SB, OR=1.424, P =8.32E-11; LNSP, OR=2.777, P =2.14E-11). In the
MVMR, EA, SB, LNSP and AFS seems to be the predominant risk factor for
MA risk with the independent effect, while HI had no effect after
controlling EA(HI in model 1, OR=0.890, P = 5.78E-01). AFB functioned as
mediators in the causal chain of MA risk reduction by EA, with the
mediated proportion of AFS and AFB being 57.8%. Conclusions:
Our MR study demonstrated the causal potential of the associations of
HI, EA, SB, LNSP, AFS and AFB with medical abortion.