- Frequency of histologic chorioamnionitis in the studied population:
A total 1400 placentas were examined during the seven months period from March to October 2020. Histologic chorioamnionitis was found in 543 placentas (38.8%), and acute funisitis was found in 237 placentas, representing less than half of those with acute chorioamnionitis (16.9%) (Table 1). The presence of acute chorioamnionitis was associated positively with chronic deciduitis (p=0.000), category 2 fetal heart tracing (p=0.001), and negatively with preeclampsia/ pregnancy induced hypertension (PIH) (p<0.000), maternal vasculopathy (p<0.000), gestational diabetes (GDM2)(p<0.001) and intrauterine fetal growth restriction (IUGR) (p<0.001). There is no association between the presence of acute chorioamnionitis and pre-term delivery at 36 weeks or earlier and other pregnancy related clinical and placental complications (Table1). However, there is clear association between histologic chorioamnionitis and pre-term delivery 32 weeks or earlier (p=0.022). The Odds ratio of acute chorioamnionitis associated with or without a variety of placental and clinical conditions are listed in Figure 1.
A total 943 placentas with CBC data and 936 CBC with differential counts were available for correlation study. Abnormally elevated white blood cell count (leukocytosis, WBC >10.3, upper limit of normal range) was found in 41.4% of the study population and abnormal neutrophil differentials (left shift, >75.6%, upper limit of neutrophil differentials) in 39.1%. Lymphopenia (lymphocyte differential less than 15.5%, lower limit of normal range) was found in 33.9%. CBC with differentials demonstrated close positive correlation with acute chorioamnionitis. Leukocytosis, left shift and lymphopenia all showed significant changes in the presence of acute chorioamnionitis. Body temperature at the time of admission and BMI were not significantly changed in acute chorioamnionitis (Table 1).
- Correlation of white blood cell count and differentials with histologic chorioamnionitis:
Acute chorioamnionitis is known to be associated with elevated white blood cells (leukocytosis) with or without left shift (increased neutrophil differentials). However, in pregnancy, the normal range of white cell counts appears widened due to the physiological changes of pregnancy, and clinical diagnostic value of white counts and differentials is somewhat altered. We examined the ranges of white blood counts and neutrophils and lymphocytes differentials in normal pregnancy and in conditions with histopathologic chorioamnionitis. We divided the white blood counts (WBC) into four groups, group 1 (normal, less than or equal to 10.3, upper limit of normal range), group 2 (10.4 to 12), Group 3 (greater than >12), and group 4 (greater than >15) (Table 2). There is a clear association between the increased WBC and incidence of acute chorioamnionitis and acute funisitis (p = 0.000 respectively) (Table 1 and Table 2). The mean of WBC, neutrophilic and lymphocytic differentials with or without chorioamnionitis were shown in Figure 2. When WBC was greater than 15 (group 4), the frequency of acute chorioamnionitis increased to 64.1%, a significant increase in comparison to that of marginal increase (group 2, 41.0%). There is also a clear association of increased WBC with increased rate of vaginal delivery (p = 0.031). Using the gestational age, WBC and neutrophil differentials as predictive values, the ROC curve for acute chorioamnionitis is less than 60% (Figure 3).
- Pre-term delivery, acute chorioamnionitis and white blood counts
There were 151 placentas of pre-term deliveries associated with a variety of clinical and placental pathologic features (Table 3). Understandably, pre-term delivery was positively associated with preeclampsia, infarcts, abruption, IUFD and twin pregnancy, but negatively associated with meconium staining of fetal membrane, chronic villitis, and umbilical cord coiling. Pre-term delivery was also associated with lower placental weight (p = 0.000). Importantly, pre-term delivery at 36 weeks or earlier was not statistically associated with acute chorioamnionitis, chronic deciduitis or acute funisitis (p=0.732). However, pre-term birth at 32 weeks or earlier showed a clear association with acute chorioamnionitis (p=0,022)(Table 1 and 3). Furthermore, pre-term deliveries before 36 weeks or before 32 weeks were not statistically associated with maternal leukocytosis, elevated neutrophil differentials (left shift) or lymphopenia (Figure 2). The Odds ratio of pre-term delivery associated with other clinical and placental pathological findings is shown in Figure 4.
- Chronic inflammatory changes (deciduitis, villitis) and white blood cells
There were 525 placentas with histologic chronic deciduitis and 331 placentas with chronic villitis. Chronic deciduitis was found to be associated with acute chorioamnionitis (Table 1) (p = 0.000), and chronic villitis was not (p = 0.191). Neither of them were associated with leukocytosis, left shift or lymphopenia. Chronic villitis was noted to be associated with fetal vascular malperfusion (avascular villi) (p=0.000) (data not shown).