The model, who is a few weeks away from her due date, was rushed to hospital on Saturday after falling ill.
Doctors are yet to give the 29-year-old a diagnosis, but she will remain under observation until at least Monday, the star's rep confirmed to MailOnline.
Scare: Danielle O'Hara, pictured shopping on Thursday, was admitted to hospital on Saturday
'Just come off drip after 24 hours now just on iv antibiotics 4 next 8 hours more & then hopefully get home to my hubby and babies tomorrow X.'
When Danielle was admitted, she was struggling to keep any food down so doctors put her on an IV drip.
Feeling poorly: Danielle tweeted from her hospital bed on Sunday eveningAlthough she is feeling much better, and her unborn baby's heart rate is good, she is happy to remain in hospital another night.
Danielle and her footballer husband Jamie O'Hara, 26, are expecting a third boy in September - a sibling for their sons Archie, three, and Harry, two.
The former Celebrity Big Brother star had a stressful pregnancy with her son Harry, who was born 10 weeks early in July 2011, weighing in at just 4lb 4oz.
When she was four months pregnant with Harry, she was also admitted to hospital with similar symptoms in March 2011.
Growing family: Danielle with her sons Archie (left) and Harry in Birmingham two weeks ago
As well as Harry's dramatic arrival, Danielle was hospitalised several times last year due to complications with her implants.
After having her previous DD-cup implants replaced with an E cup, she was admitted to hospital two weeks later after her breasts started swelling and she woke up in a pool of blood.
During removal of the implants to see what was causing the swelling, the surgeon discovered a blood clot in her chest and she required a blood transfusion. She was then re-admitted a few days later when the swelling didn't go down.
She recently admitted she had gained 35lbs during her third pregnancy, and was aiming to lose it in time for her 30th birthday bash in Las Vegas in December