They're not supposed to do a smear until 12 weeks after the birth as things are still healing up, and as such you can get called back for another one as the results were inconclusive.
Not sure about how long you should leave it after having a baby before you have a smear test but just wanted to let you know having a smear test does not hurt, it can be somewhat uncomfortable for about 3 seconds when they do the scraping of your cervix. In the past (pre-pregnancy) i went regularly for them, every 6 months, as i had abnormal cells which they needed to keep an eye on. So for the sake of 3 seconds uncomfort its worth going.
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