Main findings
In this cross-sectional cohort study, we found that i) maternal fever, fetal and maternal tachycardia, elevated leukocyte count and CRP were common findings in term deliveries complicated with chorioamnionitis, ii) the prevalence of neonatal complications was high, iii) elevated inflammatory laboratory values, and positive cervical culture were associated with an increased risk of neonatal infection, and iv) elevated inflammatory laboratory values, and fetal tachycardia were associated with an increased risk of asphyxia-related complications. Our findings highlight the importance of acknowledging signs of chorioamnionitis, and stresses the need of research focusing on identifying better predictors and preventive measurements for perinatal complications in chorioamnionitis at term gestation.
The chorioamnionitis prevalence of 0.47% in our study is considerably lower compared to previously reported rates of between 1 and 5%. However, these previously reported rates are, in general, based on older studies of placental findings of primiparous women, and are consequently not readily comparable with our results (15). Maternal fever is the most important clinical sign of chorioamnionitis, and was present in approximately 90% of the study participants. Surprisingly, maternal fever was not noted in remaining 10%, which may be a consequence of inadequate medical chart documentation rather than absence of elevated maternal temperature. Maternal and fetal tachycardia was highly prevalent (65% and 67% respectively), which is consistent with previously reported rates between 50 and 80% (16, 17). Likewise, in line with previous reports, the presence of subjective clinical signs, such as uterine tenderness and foul-smelling amniotic fluid, were rare (17). Uterine tenderness was only noted in 2% of the women with chorioamnionitis, but can be difficult to determine during active labor and the presence was only recognized if explicitly stated in the medical chart text. Hence, the prevalence of these highly subjective clinical signs is presumably underestimated.
Importantly, according to current guidelines chorioamnionitis diagnosis can only be confirmed postpartum by histopathological analysis of placenta and/or positive cervical culture (2). Therefore, we must rely on clinical signs and laboratory markers of infection when diagnosing and managing patients with suspected chorioamnionitis in clinical practice. Suspected chorioamnionitis should imply initiating treatment with broad-spectrum intravenous antibiotics, careful monitoring and labor progression should be ensured (2). Although standard obstetric indications for cesarean delivery apply in deliveries complicated by chorioamnionitis, the myometrial contractility can be affected by the inflammation, leading to an increased risk of labor dystocia, cesarean deliveries and postpartum hemorrhage (18, 19), which presumably explains the observed high cesarean delivery and postpartum hemorrhage rate in our study.
Chorioamnionitis is an established risk factor for early- and late-onset neonatal sepsis (10), and its presence motivates intensified monitoring, testing, and sometimes empiric antibiotic treatment of the neonate. Multiple attempts to develop prediction models of the risk of developing neonatal sepsis have been made, not the least in order to reduce the usage of empiric antibiotic treatment, which has been associated with an increased risk of negative childhood outcomes, including asthma (20). The impact of clinical and laboratory characteristics of chorioamnionitis on the risk of neonatal complications has not been addressed in detail previously. We found that a moderately elevated first leukocyte count, highest maximum CRP level, and positive cervical culture were associated with neonatal infection, and that high maximum CRP and fetal tachycardia were associated with asphyxia-related complications, which is partly a novel finding. Fetal tachycardia in the presence of maternal fever is a known predictor of adverse neonatal outcomes, and may be a sign of fetal inflammatory response, which has been proposed as a mechanism of impaired short- and long-term neurological outcomes (21, 22). A release of fetal pro-inflammatory cytokines, in response to inflammation, has been hypostasized to have a direct toxic effect on the brain leading to adverse neurological outcomes (12).
A culture was sent in only 70% of cases and of these, only 40% were positive. However, during the medical chart review it was noted that a majority of patients were treated with intravenous antibiotics prior to the culture being taken, which could distort bacterial growth and lead to false negative cultures. Additionally, there is emerging evidence of chorioamnionitis being a clinical syndrome with various etiologies, whereof intra-amniotic infection is one, and sterile intra-amniotic inflammation is another (23). In fact, similar with our result, previous studies report low rates of bacteria isolated from cervical or amniotic fluid cultures in patients with chorioamnionitis (24, 25).