Pre-natal multivitamin and Levothyroxine have no known drug interaction and doesn't affect on each other absorption.
So you shouldn't worry.
And take your Levothyroxine next dose as per scheduled.
It would be recommended to take the Levothyroxine 1 hour before or 2 hours after meals and the multivitamin with a meal. Even it's good to take Levothyroxine and pre-natal vitamin at different meals time.(breakfast-lunch)
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