I have read studies that if you have good egg quality, you should do it the day before they put your eggs back in for IVF and the day after. The study said that it incresed the chances from 26% to 48%. This is only if you have good eggs. Actu. can't help with that. I assume if you are doing IUI you could do the same technique - do it right after you ovulate as it builds up the lining of your uterus.
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Good Luck!