Sophie, 49, was visiting the hospital on Tuesday to open its new neonatal unit.
The medical centre holds a particularly special place in Sophie's heart, as it was the hospital where she gave birth to her two children — Lady Louise Windsor and James, Viscount Severn. The youngsters were the first royal children to be born at an NHS hospital.
Sophie looked particularly moved to be visiting the Surrey hospital, located close to her family home of Bagshot Park.
Hospital CEO Andrew Morris gave a speech in which he talked about the vital work the hospital had done in saving babies' lives. Sophie welled up as she listened to Andrew's speech and unveiled a plaque to mark the new neonatal ward.
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As she toured the unit, the gracious royal hugged midwifery staff and praised them for their work. Sophie met children and several of the hospital's youngest patients, some of whom were born as early as ten or 11 weeks premature.
Wearing a pink jacket and navy skirt, Sophie looked elegant as usual. The royal was presented with a beautiful bouquet of yellow and purple flowers and thanked staff and the Frimley Park Hospital charity for inviting her back to the hospital as a guest of honour.
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She also harked back on her own experience when she was rushed to the hospital for the birth of her first child Lady Louise.