NFP is not a good method to prevent pregnancy.
The data that shows NFP as being nearly as effective as hormonal birth control is
EXTREMELY CHERRY-PICKED.
In the best studies for NFP, the women are all young with regular, clock-work cycles. Not all women are young, not all women have clock-work cycles.
In the best studies with NFP, failures are often reported as “withdrawals” rather than failures. These good Catholic girls knew they were participating in a study they knew Mother Church wanted to succeed. So instead of sullying the study with their pregnancy, they reported that they
meant to get pregnant, so the study didn’t take a hit.
In secular literature, NFP trials undergone by folks who don’t have a religious reason to engage in puffery show that NFP is about as effective as sloppy birth control usage.
Bit I’ll agree that when it’s a Catholic study with Catholic girls, NFP looks very, very effective. That’s because bias is real, particularly when religion is involved.
I’m not understanding why you think a child’s life in the womb is “cancellable”.
It poses a potential threat to the mother, so as a matter of law it’s cancellable.
It poses a threat to her long term survival, so as a matter of nature it’s cancellable.
If she undergoes extreme shortage of nutrition, mammals are capable of self-terminating their pregnancies.
Moms gotta survive. She’s priority #1.
The contents of her womb are inherently labeled “OPTIONAL”. Mom comes first.
Therefore don’t have children. And since we know what causes children don’t engage in causal behaviors…
An answer that ignores biological drives that are much, much, much older than religion is an answer that simply can’t be taken seriously.