IUI timing

I've had four cycles of IUI (natural cycle, with donor sperm), two each at different clinics due to moving within the last two years. I'm thinking of trying again, but I was anxious because each clinic gave me conflicting advice, and though I followed each set of instructions meticulously, it did make me question the precision of timing, with the result that I don't know which is best. One clinic had me test for ovulation midday and evening; the other had me test with first morning urine, once a day only (they insisted on that), and then treated the following day after a positive result. That means there was a range of 24-48 hours in treatment timing post positive ovulation test.
Some ovulation kits say that you shouldn't test with first urine of the day because most women have a surge early in the morning but it takes hours to show up in the urine (which would make that the surge day??); a digital test I used most recently says you should only test first thing after your longest sleep (meaning that you might pick up the surge 12 hours after it actually started the previous afternoon).
Why would one clinic ask for tests first thing and another the opposite? It's a lot of money to spend (even on the kits, let alone treatment!) so some advice and reassurance about timing would be really welcome before I try again. Thank you!

Our Expert's Answer

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It is difficult for me to comment on advice from another clinic.  We base our advice on years of practice alongside blood monitoring for the LH surge and would agree with the clinic which advises testing with a digital kit first thing in the morning.  Testing twice a day only confuses the issue.  The egg will be released approximately 38- 40 hours after the onset of the LH surge which usually starts in the early hours of the morning. We have good results inseminating the day after the surge is detected and have had success inseminating 2 days after that indicating a large window of opportunity.