1 Perinatology Research Branch, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Detroit, MI, USA
2 Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Hutzel Women's Hospital, Detroit, MI, USA
3 William Beaumont Hospital, Royal Oak, MI, USA
4 Department of Obstetrics and Gynecology, Pontificia Universidad Católica de Chile, Santiago, Chile
5 Center for Perinatal Research, Sótero del Río Hospital, Santiago, Chile
6 Seoul National University College of Medicine, Seoul, South Korea
7 USARIID, Frederick, MD, USA
8 Department of Obstetrics and Gynecology, Soroka University Medical Center, Ben Gurion University of the Negev, Beer Sheva, Israel
Objective: The fetal inflammatory response syndrome (FIRS) is associated with impending onset of preterm labor/delivery, microbial invasion of the amniotic cavity and increased perinatal morbidity. FIRS has been defined by an elevated fetal plasma interleukin (IL)-6, a cytokine with potent effects on the differentiation and proliferation of hematopoietic precursors. The objective of this study was to characterize the hematologic profile of fetuses with FIRS.
Study design: Fetal blood sampling was performed in patients with preterm prelabor rupture of membranes and preterm labor with intact membranes (n=152). A fetal plasma IL-6 concentration ≥11 pg/mL was used to define FIRS. Hemoglobin concentration, platelet count, total white blood cell (WBC) count, differential count, and nucleated red blood cell (NRBC) count were obtained. Since blood cell count varies with gestational age, the observed values were corrected for fetal age by calculating a ratio between the observed and expected mean value for gestational age.
Results: 1) The prevalence of FIRS was 28.9% (44/152); 2) fetuses with FIRS had a higher median corrected WBC and corrected neutrophil count than those without FIRS (WBC: median 1.4, range 0.3–5.6, vs. median 1.1, range 0.4–2.9, P=0.001; neutrophils: median 3.6, range 0.1–57.5, vs. median 1.8, range 0.2–13.9, P<0.001); 3) neutrophilia (defined as a neutrophil count >95th centile of gestational age) was significantly more common in fetuses with FIRS than in those without FIRS (71%, 30/42, vs. 35%, 37/105; P<0.001); 4) more than two-thirds of fetuses with FIRS had neutrophilia, whereas neutropenia was present in only 4.8% (2/42); 5) FIRS was not associated with detectable changes in hemoglobin concentration, platelet, lymphocyte, monocyte, basophil or eosinophil counts; and 6) fetuses with FIRS had a median corrected NRBC count higher than those without FIRS. However, the difference did not reach statistical significance (NRBC median 0.07, range 0–1.3, vs. median 0.04, range 0–2.3, P=0.06).
Conclusion: The hematologic profile of the human fetus with FIRS is characterized by significant changes in the total WBC and neutrophil counts. The NRBC count in fetuses with FIRS tends to be higher than fetuses without FIRS.
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