Study participants
All term deliveries in the Stockholm Region between January
1st 2014 and August 31st 2020
complicated by chorioamnionitis, defined as a registered diagnosis in
the Swedish pregnancy register (ICD-10 O41.4) were identified.
From these, a random sample of 500 was identified and made up the study
population. Recently, an expert panel of maternal and neonatal experts
recommended dividing chorioamnionitis into the three separate categories
‘Isolated maternal fever’, ‘Suspected chorioamnionitis’, and ‘Confirmed
chorioamnionitis’ (Supportive information, eTable 1)(2). Based on this
categorization, and for the purpose of this study, ‘Isolated maternal
fever’ is defined as at least 1 registered maternal temperature between
38.0°C and 38.9°C, and no additional signs of infection. ‘Suspected
chorioamnionitis’ is defined as i) ≥ 1 registered maternal temperature ≥
39.0°C or ii) ≥ 1 registered maternal temperature between 38.0°C and
38.9°C in combination with at least one clinical sign of infection of:
fetal tachycardia (>160 beats per minutes [bpm] for 10
minutes or longer), maternal leukocytosis (leucocyte count
>15,000 cells/mm3), or purulent discharge
from the cervical os. ‘Confirmed chorioamnionitis’ is defined as i) a
positive culture from cervix or amniotic fluid, confirming the presence
of bacteria or ii) placental histopathological changes typical for
chorioamnionitis. The registered chorioamnionitis diagnosis in the
Swedish Pregnancy Register has not previously been validated, wherefore
we validated the chorioamnionitis diagnoses of the study cohort against
medical chart information. In total, 49 (9.8%) fulfilled the criteria
of isolated maternal fever, 397 (79.4%) of suspected chorioamnionitis
and 151 (30.2%) of confirmed chorioamnionitis. The corresponding
positive predictive value of chorioamnionitis overall was excellent
(0.92 [95% CI 0.89-0.94]) (Supportive information eMethods 1 and
eTable 2).