The 32-year-old singer, who is expecting a baby with 5ive star Ritchie Neville, began feeling unwell during the reception at a luxury hotel in Gloucester, England after her longtime pal exchanged vows with George Kay.
She was admitted to Southmead Hospital in Bristol, England and spent 24 hours under the care of a midwife before being discharged.
Hamilton later posted a message to fans on her Twitter.com page, writing, "Well what an eventful 48 hours I've had! Totally exhausted & glad to be home. Thanks to all at #SouthMeadHospital who took care of us."
Neville adds, "Wasn't expecting to spend the night in hospital with @NatashaOfficial it's been a long day and night but all is okay."
The baby is the couple's first child together. Hamilton has three other kids from previous relationships.