The same thing has happened to me. I've sworn that I O'ed early but ultrasound proved otherwise. This last cycle I believe that I O'ed the day before my IUI and I got pregnant so it can still happen if the egg is still hanging out or maybe if you dtd recently enough.

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Me-30 (anovulatory)
DH-29 ("super sperm")
8 failed IUIs
1 ectopic
1 miscarriage
Moving on to IVF
10/08-tentative egg retrival
10/11-possible embryo transfer