The X Factor star posted the image to Instagram on Wednesday (6 August) alongside a string of heart emojis.
Rebecca's fans were quick to leave a string of sweet messages, including one which read: "The baby looks so peaceful and content. It won't be long now before she's in your arms."
The Liverpool singer announced her third pregnancy in April and later confirmed it would be a baby girl. She has not publicly disclosed who the father is.
She tweeted: "Feel a special bond because when everybody said you was wrong I fought for you. I held my ground and said every child has a right to live. Feel like God blessed me with someone who I know will always bring me joy, my princess, my precious unborn Arabella."
Rebecca – who is already a mum of two – is currently over in Los Angeles working on her new album.
Before flying out she celebrated her 28th birthday. "Thankful for another year at 28. Thankful for all I have and all I have achieved. I live the life I always wanted. Caring what other people think. Has robbed me of so many minutes hours and days of what is already a temporary existence #stoppedgivingafk."
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Watch Rebecca Ferguson's video for 'I Hope' below: