The surge of the luteinizing hormone specifically triggers the egg to be released (ovulation). Therefore, I don't believe you could get an LH surge after ovulation.
Are you wondering about picking up the LH surge via OPK's - if that is your question, then some ladies are not able to detect the surge (this is for a variety of reasons - often timing) so, therefore, you could be pregnant if you have not detected the surge - so long as it actually happened and you have actually ovulated.
Have you had a +OPK after the time you thought you ovulated?
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