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Being pregnant is strenuous enough - how do these women shed the baby weight so fast?

The new Us Weekly cover shows Christina Aguilera (who gave birth to son Max in January of this year) with her bangin' post-baby bod. Damn, girl, you lost 40 pounds in 4 months? Crazy!

But while Christina's waist size has slimmed down, the same cannot be said for her bust. "It's kind of hilarious," she says. "I've never fit into an E-cup before. We keep the tags that prove it, to look back for memory's sake!"

An E-cup? For real? Go you, Christina!