Well I've taken a few science classes in my day, but that doesn't make me right. It would be nice if we had some study that investigated whether or not there was an effect on the endometrium if a woman took a single dose of Ella after ovulation. Well, in fact, there is...
I have the full text, and what is reveals is pretty clear. The investigators gave women a single dose of ulipristal (labelled cdb-2914 in the study) after they had ovulated. They then measured the effect of the medication on the endometrial lining, both histologically and with ultrasound. They measured 3 doses, 10mg, 50mg, and 100mg (the dose of Ella is 30mg). Did these doses have any effect on an embryo's ability to implant? Clearly, the answer is yes:
CDB-2914 also was associated with decreased expression of peripheral node addressins (PNAds), which are important L-selectin ligands found on the surface of endothelial cells. Recent studies have shown that L-selectin ligands are up-regulated during the implantation window, making the uterus more receptive to the trophoblast (17,18).In other words, there is direct evidence that Ella decreased the action of endometrial cells that are known to be important for implantation.
Although a thicker endometrium might be expected in those with continued endometrial proliferation after an antiprogestin, in this study, women with proliferative endometrium on mid-luteal biopsy did not have a thicker endometrium. Either effect of CDB-2914, endometrial atrophy or continued proliferation,however, may hamper implantation.Here the authors acknowledge directly that Ella may hamper iplantation if taken after ovulation has occurred. Its hard to get any clearer. Even the summary acknowledges this:
In summary, decreased endometrial thickness and decreased L-selectin ligands expression may be the earliest features of the antiprogestational effect of CDB-2914 in the luteal phase, heralding other endometrial changes. In our studies, endometrial maturation appeared to be more vulnerable to a small, single dose given in the follicular phase than with a single dose given either in early or mid-luteal phase. Whether this is a direct endometrial effect or secondary to an ovarian effect is not known. Taken together, these endometrial effects in the absence of ovarian and menstrual cycle effects suggest mechanisms by which CDB-2914 might be effective as an emergency contraceptive (28).Science is a stubborn thing. We now have experimental evidence that Ella has an effect on the endometrium that can act to prevent an embryo from implanting. The burden of proof is now on the other side to give evidence that this is wrong - which almost certainly they will not do. Its far easier to insult us.
This is especially important considering the latest news about Plan B. Because of its ineffectiveness, more and more women will be encouraged to take Ella (especially since cost is no longer an issue).