That's a very cool idea! You could call it the Princess and the Pea (like the Pea in the Pod maternity line), or with the Lady Godiva wig, you could be Rapunzel -- with evidence of how the Wicked Witch realized she was having *ahem* visits from the Prince! Great idea!
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Pair a Lady Godiva wig or one of similar length with your favorite maternity dress. Preferably empire waist or renaissance style.