Mine didn't start at all with Ds ... Waters broke at 3am, they induced me 2 days later at 12:30pm. (33.5hrs later, they wern't supposed to let me wait that long apparently??)
apparently after 12 hours infection can set in. because ds2 wasnt born untill arround 18hours after mine broke, i copped a huge ear bashing of one midwife and both ds2 and i had to have antibiotic drips and blood tests every few hours for a few days "just to be sure" due to the time frame.