Just for fun because I'm a science dork, I found another great journal article about why not to douche. It actually explains how douching can cause ectopic AND miscarriage.
"An added concern is that, if douching reduces the density of normal vaginal flora, bacterial vaginosis might develop or there may be a predisposition to colonization by such sexually transmitted pathogens as Neisseria gonorrhoeae or Chlamydia trachomatis, filling the “ecologic niche” (16). Pathogenic bacteria may then ascend into the upper reproductive tract, leading to inflammatory scarring (endometritis, salpingitis, or peritonitis), the principal cause of ectopic pregnancy, early miscarriage, and infertility (16)."
Vaginal Douching: Evidence for Risks or Benefits to Women
So basically douching can increase risk of bacterial vaginosis which is related to ectopic, miscarriage, and yeast infections. I know on IG lots of the women had to take probiotics to ward off the yeast infections caused by all the douching.