Gomez-Lopez N, et al. - The origin of amniotic fluid neutrophils from women with intra-amniotic infection and/or inflammation was examined. In addition, the authors aimed to correlate these findings with acute histologic maternal and fetal inflammatory responses in the placenta. In women with intra-amniotic infection and/or inflammation, amniotic fluid neutrophils could be either predominantly of fetal or maternal origin, or a mixture of both fetal and maternal origin. Herein, the findings gave evidence that both fetal and maternal neutrophils could invade the amniotic cavity, implying that both the fetus and the mother participated in the host defense mechanisms against intra-amniotic infection.

• The authors collected amniotic fluid from 15 women with suspected intra-amniotic infection and/or inflammation (positive microbiological cultures and/or interleukin (IL)-6 concentrations≥2.6 ng/mL).
• By using fluorescence-activated cell sorting, amniotic fluid neutrophils were purified, DNA was extracted, and DNA fingerprinting was performed.
• Moreover, they performed DNA fingerprinting in the umbilical cord and maternal blood DNA.
• They assayed fluorescence in situ hybridization (FISH) in women with male neonates.
• They conducted blinded placental histopathological evaluations.

• 42.8% (6/14) of the women who underwent a single amniocentesis had mostly fetal neutrophils in the amniotic fluid as revealed by DNA fingerprinting.
• This fingerprinting also demonstrated that 35.7% (5/14) of the women who underwent a single amniocentesis had predominantly maternal neutrophils in the amniotic fluid.
• In addition, DNA fingerprinting showed that 21.4% (3/14) of the women who underwent a single amniocentesis had an evident mixture of fetal and maternal neutrophils in the amniotic fluid.
• A woman who underwent two amniocenteses (patient #15) reported fetal neutrophils first, and as infection progressed, abundant maternal neutrophils were found to invade the amniotic cavity, noted via DNA fingerprinting.
• By showing that both fetal and maternal neutrophils were presented in the amniotic fluid, FISH confirmed DNA fingerprinting results.
• At the time of collection, most of the women who had predominantly amniotic fluid neutrophils of fetal origin delivered extremely preterm neonates [71.5% (5/7)].
• Women who had predominantly amniotic fluid neutrophils of maternal origin at the time of collection delivered term or late preterm neonates [100% (6/6)].
• At the time of collection, 2 of the women with an evident mixture of fetal and maternal neutrophils in the amniotic fluid delivered extremely preterm neonates [66.7% (2/3)], and the third woman delivered a term neonate [33.3% (1/3)].
• In this study, most of the women included presented with acute maternal and fetal inflammatory responses in the placenta [86.7 % (13/15)].