The 33-year-old singer posted the bare-all photo to her social media to promote the We Are Here charity movement after a friend asked what her purpose was in the world.
Alicia told the New York Times: "Nobody had asked me that question before."
The question got her thinking about things she wanted to achieve and so she decided she wanted to encourage her 35 million fans on Facebook and 20 million followers on Twitter to get involved with social justice causes.
The mum-of-one said: "I want to gather an army."
She posed in the nude with a peace sign on her baby bump to get people to pay attention.
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Alicia, whose husband is Swizz Beatz, continued: "It's time to get people's attention. People won't be able to ignore this visual."
She aims to spread awareness of issues from stricter gun laws to criminal justice reform, from gay rights to global girls' education.
Alicia is expecting her second child in December and she wants her baby to be born into a 'kinder and more peaceful world for all children'.
She is already mum to three-year-old Egypt.
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