Naegele's Rule Was Published in 1812. Your Due-Date Calculator Still Uses It Alone.

ACOG Committee Opinion 700 defines a 5-tier ultrasound-vs-LMP discordance table (5d / 7d / 10d / 14d / 21d) for redating an EDD. Top-ranked consumer due-date calculators apply LMP + 280 days and stop. This one computes both, picks per the threshold table, and uses Robinson-Fleming CRL with the BMUS 1.037 correction.