I wanted to investigate the length of time between rupture of membranes and risk of chorioamnionitis, an infection of the membranes including the amnionic sac, placenta, amnionic fluid, and even fetus itself. Chorioamnionitis occurs when bacteria ascends the reproductive tract after the rupture of membranes. My study material (Blueprint) listed prolonged rupture of membranes, greater than 18 hours before delivery, to be a risk factor for developing chorioamnionitis. However, in my last history and physical the providers treating the patient seemed concerned about preventing the development of chorioamnionitis in a patient who was 2cm dilated after rupture of membranes approximately 8 hours later. I assumed this was because by the time she delivered it could be over the 18 hour mark, but it made me wonder more about if there is a risk of chorioamnionitis before this 18 hour mark.

“Length of Rupture of Membranes in the Setting of Premature Rupture of Membranes at Term and Infectious Maternal Morbidity” is a retrospective cohort study examining whether the length of time from rupture of membranes to delivery in term births is associated with maternal infectious complications, chorioamionitis and endomyometritis. The study consisted of 3,841 patients with term premature rupture of membranes. The researchers analyzed the interval between rupture of membranes and delivery in two hour increments to see how infection rates increased.

The study found that chorioamionitis risk increased significantly when rupture of membranes was 12 hours or more before delivery and endomyometritis risk increased significantly at 16 hours or more. Additionally, the risk of chorioamionitis was 2.3 times higher at 12 hours or greater and 2.5 times higher for endomyometritis at 16 hours or more. Additionally, the study found that there was a risk of infection in prolonged rupture of membranes beyond 8 and 10 hours as well, although not as high as at the 12 hour mark. Therefore, the study concluded that the longer duration between membrane rupture and delivery the higher risk of infection and that this risk doesn’t plateau rather increases over time.

Although my study material listed the risk factor as 18 hours or greater, it seems like the risk is high before that, at 12 hours or more which gives more context to my clinical case. In regards to patient management, it supports the decision to give pitocin to augment labor before the 12 hour mark rather than waiting for that 12 hour mark in order to minimize chances of infection.