Breast feeding is still, today, worldwide, the biggest factor in postponing follow-on pregnancies, or so they say at the WHO.
And charting (with periodic abstinence) while postpartum/breastfeeding has gotten a lot better too, or so they say. I don't have any good anecdotes on that (and I know the plural of anecdote is not data!!) but my husband and I only used NFP to better achieve pregnancy, not postpone it.
Congrats on the kid! Deus vult!
Problem is, you're fertile before there's evidence if it, if you get my drift.
You can't use timing if you don't know you can get pregnant.
ooops.....
It gets down to, if God wants you to have that baby, you will, no matter what you try to do to prevent it otherwise.
I know lots of cases of even the (allegedly) best of surgeries, which have failed.
Anyway, breastfeeding's biggest health benefit for the mother, is it's protective action against breast cancer.