Very good points; thanks for the excellent comment!

‘the rhythm method’ is NOT
“the only form of birth control approved by the Catholic Church”!!

You might as well say that
‘the Model-T Ford is the only form of automobile approved by the Catholic Church.’ [*Acts of the Apostles* plainly tells us without any sign of disapproval that they 'were all of them in one Accord'].

Seriously, though, my point (which seems to escape an astonishing number of doctors and scientists regarding ‘rhythm’ is that
for decades now, natural family planning methods have advanced in precision and power about as much as the Accord’s ignition system exceeds the crank of the Model-T!

In short,
modern methods of NFP depend on EXTREME accuracy in detecting the moment an oocyte is released into the Faliopian tube,
rather than making hopeful predictions based on the average length of a woman’s fertility cycle.

THIS elementary fact NEEDS to be brought to PUBLIC ATTENTION!!!

Very much in second place, the assertion that embryo viability is cycle-based may or may not be validly supported by evidence (I know of none); wait and see…

Finally, from the moral point of view,
the question of the impact of a cyclic viability effect on a couple’s knowledge and intentions in choosing a particular moment for the marriage act would remain. Are they deliberately choosing to put the embryo at absurdly high risk of death for selfish reasons? Then, and ONLY then, do I think there’s a problem.

There are so many holes in that logic I couldn’t count them. It’s not a question of viability of the embryos, because 1/3 of all fertilized embryos do not implant in the uteran wall.

It has everything to do with our intrusion in the process – whether we INDUCE something or not. Natural Family Planning means we keep life and death in the hands of God; where it should be.