A Licit Device to Prevent Pregnancy?

Credit: eglisetraditionaliste.org

Every few years the story about the "nuns in the Congo" that a pope (usually it's Bl. Pope Paul VI) said could take birth control resurfaces. Inevitably there are debunkers and rebunkers. It's very hard to find original documentation on this question, even in the age of the internet, because it was apparently all internal memos from theologians.

The story causes lots of confusion, but probably shouldn't because A) there was more estrogen in pills back then, so they probably were all truly anti-ovulant, B) it wasn't known that pills could even be contra-gestive or abortifacient, and C) emergency contraception (i.e. anti-ovulation or anti-fertilization in nonconsensual intercourse) is even now viewed as legitimate in Church teaching.

Nevertheless, every time the story arises, I think to myself: what sort of intervention could be licit in such a situation?

The problem is this: I need effective pregnancy prevention without post-fertilization effects. An ideal intervention would be anything that prevented fertilization only, such as something that inhibited cervical fructose production, capacitation, or the acrosome reaction. Of questionable permissibility would be something to inhibit the zona reaction (preventing the thick rind of chemicals around the egg from hardening), which would allow polyspermy and lead to a nonviable embryo. If life begins at sperm-egg fusion (which I find compelling) then allowing polyspermy would allow some viable embryos to become nonviable due to increased chromosome content.

But none of that technology exists. Just considering existing technologies, the most effective preventative devices are hormonal, but the only licit ones are barriers, and those mostly rely on male cooperation (or don't prevent STDs, like the diaphram). Hormonal strategies are illicit because they have post-fertilization effects. Going back to the doses of estrogen that pills contained in the time of Pope John XXIII is unsafe for women.

What I'm about to say does not come from an ethicist, a Church official, or even someone with a real degree in theology. 

A diaphragm. Just for clarity: the Catholic Churchis very clear that barrier contraceptives like
diaphragms are gravely sinful in marriage.

So, I guessed, maybe I need a barrier with hormonal-but-not post-fertilization effects. Maybe (this sounds really uncomfortable but hang on) a diaphgram plus or minus a cervical extension designed to go to (but not past) the endocervical os. The device could have a very, very low concentration of  levonorgestrel in it, so low that it had only autocrine effects on the cervical crypts only, and not on endometrial tissue or ovaries. Perhaps levonorgestrel would have too long a half life, and we'd have to synthesize a shorter-acting progesterone or one that had a long half life in an inactive form, then a short half life in an active form.

The result would probably be a ton of mechanical cervicitis. But (maybe) no postfertilization effects and effective pregnancy prevention. You could decrease the rate of cervicitis by using it only during your fertile window. (And maybe the diaphragm part of it could include a BBT thermometer component so that the device itself could tell you when to take it out, or an app connected to the device.)

But is this a good thing? Is it a crutch that would just act like another LARC, or would it help women (especially those who learned to chart so that they could use it only 5-10 days a month)? Would it drive us even deeper into the culture of death by helping people in absurd states (e.g. these women and this woman), or would it help lift us out, until we're more ready for the ideal of everyone-married-and-using-NFP?

And where do I go now? The patent office, or the confessional?