Prince Daniel was at her side, according to Royal Court spokesperson Bertil Ternert.
Victoria arrived at the hospital at 12.50am after being driven from her home at Haga Palace in an ordinary court car.
“Everything is normal. There is nothing out of the ordinary. We've been prepared for this,” said Ternert.
Plans called for the Princess to give birth naturally and not by Caesarean section.
King Carl Gustaf XVI and Queen Silvia were at their home at Drottningholm palace when they received word that Victoria had been taken to hospital, but weren't expected at the hospital.
The Royal Court had said Victoria was due to give birth in early March, but less than a week ago the hospital began blocking off parking places in anticipation of the royal birth.
According to news agency TT's reporter at the hospital, the atmosphere there was "calm" in anticipation of a 7am announcement by Prince Daniel.
A few police cars were circling the hospital perimeters but police presence was limited and the officers said that those who needed to get to Karolinska would have no problems doing so.