Objective Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of the NO synthase pathway, and is considered as a marker of endothelial dysfunction. There are few studies on ADMA in newborns, because of technical problems and ethical implications associated to blood sampling in little babies. The aim of the present study was to measure ADMA levels in preterm infants during the perinatal period.

Methods Our laboratory developed a new method for measuring ADMA, which has high sensibility and specificity while requiring small quantities of blood (10 uL): liquid chromatography-ionization by electronebulization-tandem mass spectrometry. Plasma concentrations of ADMA were measured on blood samples collected for routine analisys from the umbilical artery in 29 preterm infants (27±1.5 wks., 800±170 g), at birth and during the first week of life. Infants were then divided into 2 groups according to the presence of corioamnionitis, defined as placental surface inflammation at microscopic histopathological analysis.

Results ADMA concentrations were 0.79±0.3 umol/L at birth and did not decrease during the first week of life. The 12 infants with corioamnionitis had higher ADMA levels both at birth (0.99±0.35 vs 0.66±0.17 umol/L) and during the first week of life (0.84±0.13 vs 0.57±0.19 umol/L on day 7) in comparison to infants with no evidence of chorioamnionitis (P<0,005).

Conclusions ADMA levels are higher in preterm newborns with chorioamnionitis; these data suggest that ADMA may play a role in the complex molecular mechanisms and modifications occurring in placental and fetal inflammation.