I was having a discussion with a non-Catholic friend of mine a little while ago. Years ago I had explained to her why using a hormonal IUD or the pill for medical reasons was allowed but only if the user was not sexually active, as it could result in fertilization but would not allow the baby to implant. She understood that and life went on.
Recently, we were discussing some problems I was having and I mentioned that partial hysterectomy (where they remove the uterus but not the ovaries) was on the table as one of the options. I know that it is allowed (for medical purposes of course) and there seems to be no discussion of not allowing intercourse afterwards. She pointed out, though, that while ridiculously unlikely, it is possible for fertilization to occur after a partial hysterectomy, and those fertilized eggs usually end up not being able to implant, or if they do often they result in an ectopic pregnancy. Only in exceedingly rare cases can the baby implant on the abdominal wall and develop (later to be delivered by C-section). She then asked what the difference was between that and a hormonal IUD or the pill and I had no answer for her.
My husband and I practice NFP so we know the ins and outs of cervical fluid, and it occured to me that without a cervix, there would be no cervical fluid and without that sperm are basically useless. So that seemed to be a possible explanation, but it is still technically possible for fertilization to occur so I’m kind of stumped. Anyone with a better explanation (both for my sake and for hers)?