EDD+4

[reading: Christopher Brookmyre, "The Sacred Art of Stealing"]

I've finally found the answer to a question I've wondered about for six months now: which is a more accurate estimator of EDD, LMP or ultrasound scan (BPD).

Of course, the answer doesn't matter that much—things happen when they happen. But I was a bit bemused that none of the medical folk I asked knew the answer, and more bemused that most of them didn't even understand the question.

Looks like the answer is: BPD.