Ciara has lost 60 pounds since giving birth to her baby son four months ago.

The 28-year-old singer welcomed her first child Future Zahir Wilburn in May and wasted no time getting her pre-baby figure back with a gruelling fitness routine.

Taking to her Instagram account last night (03.10.14), she posted a snap of her in black Calvin Klein underwear, which she accompanied with the caption: ''I feel so proud to say that 4 months after delivering a 9lbs. 10 oz. baby, I can finally rock My Calvin's! #mycalvins (sic).''

She then added another snap, this time wearing grey underwear, with the caption: ''After Delivery My Son I Feel Like There's Nothing I Can't Do. I Feel Like I Can Conquer The World #ANewMe #NewMusic. So Proud To Rock #mycalvins 60lbs later!! (sic).''

The 'Like a Boy' hitmaker's personal trainer Gunnar Peterson believes the brunette beauty has sprung back into shape so quickly with a combination of healthy eating, regular sleep and daily exercise.

He said previously: ''She's working hard, she's getting it done, she's eating properly, she's getting sleep while she can, and so she's getting leaner and stronger. That's the way to be the best mum.

''It's about keeping her moving. There are a lot of intervals in there. It doesn't make for a happy camper, but [it produces] great results.

''You see the body, she's already right there.''

Meanwhile, Ciara has recently rekindled her romance with her son's father Future after they split up in July amid rumours he was having an affair with his stylist.