hi jac_horse
BBT is not a a good indicator, it is easily influenced by many factors eg. stress, flu, etc. i only ovulate on CD18, and by then my follicle was about 20mm. So, 15mm on D12 seems to be ok for my case. In fact, the only way to find out whether u have any hormonal probs is thru blood test, BBT is not a good indicator. Hey dun feel despair. Why dun u check with dr about this? Before u start anything on IVF, he will do a blood test for u. So u should use that as a benchmark whether to go ahead with IVF, not BBT. In fact during IVF, u need to do quite a number of blood tests to see if ur hormones are ok. Dr will use that to decide on the dosage for the IVF medications.