Abstract
Objective. Funisitis is the histologic counterpart of the fetal inflammatory response syndrome, which is a multisystemic disorder associated with impending preterm delivery and adverse neonatal outcome. The purpose of this study was to examine the relationship between funisitis and the microbiologic status of amniotic fluid (AF) and AF white blood cell (WBC) count in patients at term.
Methods. The relationship between the presence of funisitis, AF culture, and AF WBC count was examined in 832 consecutive patients who delivered a term neonate within 72 hours of amniocentesis. AF was cultured for aerobic and anaerobic bacteria, as well as for mycoplasmas. Funisitis was diagnosed in the presence of neutrophil infiltration into the umbilical vessel walls or Wharton's jelly. AF WBC count was analyzed in a hemocytometer chamber. Nonparametric statistics were used for data analysis.
Results. Funisitis was present in 4% (30/832) of cases. A positive AF culture was more common in cases with funisitis than in those without funisitis (17% vs. 5%; p < 0.05). Patients with funisitis had a significantly higher median AF WBC count than those without funisitis (median >1000 cells/mm3 vs. median 2 cells/mm3; p < 0.001). The frequency of funisitis and of a positive AF culture was 1% in women without labor and with intact membranes and the frequencies and the median AF WBC count increased in the presence of labor or rupture of membranes.
Conclusion. Funisitis is present in 4% of women at term and is associated with microbial invasion of the amniotic cavity (MIAC) and inflammation as reflected by increased AF WBC count.
Introduction
The human fetus can deploy a systemic and localized inflammatory response to microbial products Citation[1], Citation[2]. The term ‘fetal inflammatory response syndrome’ (FIRS) refers to a condition operationally defined by an elevation in the fetal plasma concentration of interleukin-6 (IL-6). FIRS has been associated with impending preterm delivery and adverse perinatal outcome Citation[1-3]. Funisitis, inflammation of the umbilical cord, represents a fetal inflammatory response and is the histologic hallmark of FIRS Citation[3],Citation[4]. Previous studies have provided evidence of an association between funisitis and adverse perinatal outcome, specifically, neonatal infection-related complications and cerebral palsy in preterm neonates Citation[3],Citation[5], Citation[6]. There is a paucity of information about the frequency and clinical significance of funisitis in term gestations. This study was conducted to examine the relationship between funisitis and the microbiologic status of the amniotic fluid and the amniotic fluid white blood cell (WBC) count in patients at term according to the labor status (labor vs. no labor) and whether or not the membranes were intact.
Methods
Study design
A retrospective analysis was conducted on 832 consecutive patients who delivered term singleton neonates (gestational age >37 weeks) within 72 hours of the retrieval of amniotic fluid via amniocentesis or at the time of cesarean delivery (this criterion was used to preserve a meaningful temporal relationship between the results of amniotic fluid studies and the histologic findings of the umbilical cord obtained at birth). The Institutional Review Board approved the collection of specimens and clinical information for research purposes. Fetal death was an exclusion criterion.
Amniotic fluid culture and WBC count determination
Amniotic fluid was obtained by transabdominal amniocentesis under ultrasonographic guidance (n = 69) or by direct puncture of the fetal membranes under direct visualization at the time of cesarean section (n = 763). Transabdominal amniocentesis was performed to evaluate the microbial status of the amniotic cavity in 69 cases with premature rupture of membranes (PROM). An aliquot of amniotic fluid was transported to the laboratory and analyzed in the hemocytometer chamber to determine the WBC count. Amniotic fluid was cultured for aerobic and anaerobic bacteria, as well as for mycoplasmas (Mycoplasma hominis and Ureaplasma urealyticum), according to methods previously described Citation[7].
Diagnosis of funisitis and chorioamnionitis
Tissue samples taken for histopathologic evaluation included the chorion-amnion, the chorionic plate, and the umbilical cord. These samples were fixed in 10% neutral buffered formalin and embedded in paraffin. Sections of tissue blocks were stained with hematoxylin and eosin. Histopathologic examination was performed by a pathologist who was blinded to the clinical information. Funisitis was diagnosed in the presence of neutrophil infiltration into the umbilical vessel walls or into Wharton's jelly. Acute histologic chorioamnionitis was diagnosed if acute inflammatory changes were present on examination of the extra-placental membranes or the chorionic plate of the placenta, according to the criteria previously published Citation[7]. Clinical chorioamnionitis was diagnosed when the maternal temperature was elevated to 37.8°C and two or more of the following criteria were present: uterine tenderness, malodorous vaginal discharge, maternal leukocytosis (≥15 000 cells/mm3), maternal tachycardia (≥100beats/minute), and fetal tachycardia (≥160 beats/minute) Citation[8].
Diagnosis of neonatal morbidity
Significant neonatal morbidity was defined as the presence of any of the following conditions: congenital neonatal sepsis, respiratory distress syndrome, congenital pneumonia, bronchopulmonary dysplasia, intraventricular hemorrhage (grade ≥II), and necrotizing enterocolitis. These conditions were diagnosed according to definitions previously reported in detail Citation[7]. Congenital neonatal sepsis was defined in the presence of a positive blood culture result within 72 hours of delivery.
Statistical analysis
The Student's t-test, Chi-square test, Fisher's exact test, and Mann–Whitney U test were used as appropriate.
Results
Funisitis was diagnosed in 4% (30/832) of cases. displays the clinical characteristics and outcomes of patients according to the presence or absence of funisitis. Funisitis was associated with a lower mean maternal age, a higher proportion of nulliparity, a higher median gestational age at delivery, and a higher mean birth weight.
Table I. Clinical characteristics and outcomes of the study population according to the presence or absence of funisitis.
The prevalence of acute histologic chorioamnionitis and of positive amniotic fluid cultures was significantly higher in patients with funisitis than in patients without funisitis. Patients with funisitis had a significantly higher median amniotic fluid WBC count than those without funisitis (, p < 0.001).
Figure 1. Amniotic fluid WBC count according to the presence or absence of funisitis. The median amniotic fluid WBC count for patients with funisitis was significantly higher than that for patients without funisitis (median >1000 cells/mm3; range 0–>1000 cells/mm3 vs. median 2 cells/mm3; range 0–>1000cells/mm3; p < 0.001).
Patients were divided into five groups according to the presence or absence of labor, and the status of the membranes at the time of retrieval of amniotic fluid: group 1, women with intact membranes and without labor (n = 566); group 2, women with PROM and without labor (n = 68); group 3, women with PROM and in labor (n = 26); group 4, women in labor without rupture of membranes (n = 94); and group 5, women in labor with rupture of membranes (n = 78).
The frequency of funisitis and of a positive amniotic fluid culture for microorganisms was 1% in women with intact membranes and without labor (group 1) at term and the frequencies increased in the presence of labor or rupture of membranes. Similarly, the median amniotic fluid WBC count increased in the presence of labor or rupture of membranes ().
Table II. Funisitis, positive amniotic fluid culture, and median amniotic fluid WBC count according to the presence or absence of labor and the status of the chorioamniotic membranes.
displays the clinical and laboratory findings for the five cases of isolated funisitis; all patients had a negative amniotic fluid culture.
Table III. Characteristics of five cases of isolated funisitis.
Discussion
Principal findings of this study
(1) Funisitis was detected in 4% of patients who delivered at term. (2) The frequency of funisitis was 1% in women with intact membranes and without labor at term and the frequency increased in the presence of labor or rupture of membranes. (3) Funisitis was associated with microbial invasion of the amniotic cavity (MIAC), histologic chorioamnionitis, and intra-amniotic inflammation as reflected by the amniotic fluid WBC count. (4) Of the 30 patients with funisitis, none had clinical chorioamnionitis; therefore fetal inflammation can occur in the absence of clinical evidence of infection.
The frequency of funisitis in term deliveries
Pathologic studies of the placenta have traditionally focused on histologic chorioamnionitis Citation[9-12], which is mainly a maternal inflammatory response Citation[11-13]. Several decades ago, examination of the umbilical cord for the detection of funisitis was proposed as a method to assess the likelihood of congenital infection because inflammation of the umbilical cord is a fetal inflammatory response Citation[14], Citation[15]. Some advocated that frozen sections of the umbilical cord could be examined for the rapid assessment of the probability of congenital sepsis Citation[16]. Even though this practice never became widespread, interest in the detection of fetal inflammation has been rekindled by recent studies demonstrating a relationship between funisitis and adverse short and long-term outcomes (neonatal sepsis, perinatal death, chronic lung disease, cerebral palsy, etc.) Citation[3], Citation[5], Citation[6]. However, most of this information is derived from the placentas of preterm neonates. There is little information about the frequency and clinical significance of funisitis in the term gestation. The frequency of funisitis in our population is 4%. Previous studies from our institution suggest that the earlier the gestational age at birth (preterm PROM and spontaneous preterm labor with intact membrane) the higher the frequency of funisitis Citation[3].
The clinical significance of funisitis
This study indicates that funisitis in a term gestation is a subclinical condition because none of the patients had evidence of clinical chorioamnionitis. This means that substantial fetal inflammation can occur in a silent manner. It is noteworthy that the frequency of funisitis was only 1% in women who underwent elective cesarean delivery at term without labor and that the frequency increased in the presence of labor or rupture of membranes. This is not unexpected as the frequency of microbial invasion of the amniotic cavity in previous studies is known to be higher in women with spontaneous labor at term and those with PROM at term than in those not in labor at term Citation[17]. Previous studies have revealed that umbilical cord blood concentrations of interleukin (IL)-6 are significantly lower in term gestations with funisitis than in preterm gestations with the same histologic lesion and severity Citation[18]. Similarly, we have previously reported that among women with a positive amniotic fluid culture for microorganisms, the amniotic fluid concentration of IL-6 is significantly lower in term gestations than in preterm gestations Citation[19]. These observations imply that intra-amniotic inflammation and funisitis may have different clinical significance in the term than in the preterm gestation.
Funisitis, intra-amniotic inflammation, and microbial invasion of the amniotic cavity
Funisitis was significantly associated with a positive amniotic fluid culture for microorganisms and the infiltration of neutrophils into the amniotic cavity, which are not normally present in this space. These observations are consistent with those previously reported by many investigators in preterm gestations Citation[3],Citation[6],Citation[14-16]. An explanation for this association is that microbial invasion of the amniotic cavity elicits a fetal inflammatory response, which can be detected by examination of the amniotic fluid or the umbilical cord. This interpretation is in keeping with the observation that neutrophils in the amniotic cavity are of fetal origin Citation[20].
Funisitis and histologic chorioamnionitis
Most patients with funisitis also had histologic chorioamnionitis (83%,). This observation suggests that when funisitis occurs, a maternal inflammatory response has also been deployed. It is noteworthy that 17% of fetuses had funisitis without histologic chorioamnionitis. Potential explanations for this include a systemic transplacental infection, which affects the fetus but not the membranes. Alternatively, a sampling bias may occur if histologic chorioamnionitis does not involve the entire chorioamniotic membranes. Our impression is that the first explanation is not likely because we did not observe villitis, which is generally seen in hematogenous infections. Isolated funisitis has been observed in 5–8% of preterm gestations Citation[3],Citation[6] and thus it is more frequent in term gestations. Further studies are required to examine the clinical significance (short and long-term) of funisitis at term. Our sample size (n = 30) does not allow the drawing of clinical inferences at this time.
Conclusion
In conclusion, funisitis is present in a small percentage of women who deliver at term and its presence is associated with labor and rupture of membranes. This study has demonstrated an association between inflammation of the umbilical cord, MIAC, and intra-amniotic inflammation. Funisitis at term appears to have a different clinical significance from funisitis in the preterm gestation. In contrast to the preterm gestation Citation[5], funisitis at term has not been associated with cerebral palsy. This may have medico-legal implications because the presence of funisitis at term should not be equated with the pathologic processes operating in preterm fetuses.
Related Research Data
References
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