Fetal inflammatory response in women with proteomic biomarkers characteristic of intra-amniotic inflammation and preterm birth

Abstract

Objective: To determine the relationship between presence of amniotic fluid (AF) biomarkers characteristic of inflammation (defensins 2 and 1 and calgranulins C and A) and fetal inflammatory status at birth.

Design: Prospective observational cohort.

Setting: Tertiary referral University hospital.

Population: One hundred and thirty-two consecutive mothers (gestational age, median [interquartile range]: 29.6 [24.1-33.1] weeks) who had a clinically indicated amniocentesis to rule out infection and their newborns.

Methods: Intra-amniotic inflammation was diagnosed by mass spectrometry surface-enhanced-laser-desorption-ionization time of flight (SELDI-TOF). The AF proteomic fingerprint (mass-restricted [MR] score) ranges from 0-4 (none to all biomarkers present). The intensity of intra-amniotic inflammation was graded based on the number of proteomic biomarkers: MR score 0: 'no' inflammation, MR score 1-2: 'minimal' inflammation and MR score 3-4: 'severe' inflammation. At birth, cord blood was obtained for all women. Severity of histological chorioamnionitis and early-onset neonatal sepsis (EONS) was based on established histological and haematological criteria. Interleukin-6 (IL-6) levels were measured by sensitive immunoassays. The cord blood-to-AF IL-6 ratio was used as an indicator of the differential inflammatory response in the fetal versus the AF compartment.

Main outcome measures: To relate proteomic biomarkers of intra-amniotic infection to cord blood IL-6 and to use the latter as the primary marker of fetal inflammatory response.

Results: Women with intra-amniotic inflammation delivered at an earlier gestational age (analysis of variance, P<0.001) and had higher AF IL-6 levels (P<0.001). At birth, neonates of women with severe intra-amniotic inflammation had higher cord blood IL-6 levels (P=0.002) and a higher frequency of EONS (P=0.002). EONS was characterised by significantly elevated cord blood IL-6 levels (P<0.001). Of the 39 neonates delivered by mothers with minimal intra-amniotic inflammation, 15 (39%) neonates had umbilical cord blood IL-6 levels above the mean for the group and 2 neonates had confirmed sepsis. The severity of the neutrophilic infiltrate in the chorionic plate (P<0.001), choriodecidua (P=0.002), umbilical cord (P<0.001) but not in the amnion (P>0.05) was an independent predictor of the cord blood-to-AF IL-6 ratio. Relationships were maintained following correction for gestational age, birthweight, amniocentesis-to-delivery interval, caesarean delivery, status of the membranes, race, MR score and antibiotics and steroid exposure.

Conclusions: We provide evidence that presence of proteomic biomarkers characteristic of inflammation in the AF is associated with an increased inflammatory status of the fetus at birth. Neonates mount an increased inflammatory status and have positive blood cultures even in the context of minimal intra-amniotic inflammation.

Figure 1. Relationship between presence in the amniotic fluid of biomarkers characteristic of intra-amniotic inflammation and amniotic fluid (AF) and umbilical cord blood (CB) interleukin-6 (IL-6) levels

(A). Amniotic fluid interleukin-6 (IL-6) levels in women with and without intra-amniotic inflammation. (B). Umbilical cord blood IL-6 levels in neonates delivered by women with and without intra-amniotic inflammation. The MR score ranges from 0 to 4. MR score 0 (zero) indicates “no” inflammation; MR score 1-2 indicates “minimal” inflammation; MR score 3-4 indicates “severe” inflammation. Data presented in logarithmic format. (pg=picograms; mL=milliliters)

Figure 2. Relationship between the umbilical cord blood (CB) interleukin-6 (IL-6) levels, early onset neonatal sepsis (EONS) and absolute neutrophil cont

(A). Umbilical cord blood IL-6 levels in neonates diagnosed with or without EONS. (B). Distribution of cord blood interleukin-6 levels on the Y axis in relationship to the absolute neutrophil count on the X axis. Data presented in logarithmic format. (pg=picograms; mL=milliliters, EONS=early onset neonatal sepsis)

Figure 3. Relationship between the amniotic fluid (AF) and umbilical cord (CB) blood interleukin-6 (IL-6) levels

Distribution of the AF (Y axis) in relationship to the cord blood IL-6 levels on the X axis. Data presented in logarithmic format. (pg=picograms; mL=milliliters)

Figure 4. Relationship between the umbilical cord blood (CB) interleukin-6 (IL-6)/amniotic fluid (AF) interleukin-6 ratio and histological inflammation of the placenta

(A). CB IL-6/AF IL-6 ratio in women with stages I - III histological inflammation of the chorionic plate; (B). CB IL-6/AF IL-6 ratio in women with grades 0-4 choriodeciduitis; (C). CB IL-6/AF IL-6 ratio in women with grades 0-4 funistis. Data for the CB and AF IL-6 levels are presented in logarithmic format.