Nitric oxide (NO) and adrenomedullin (AM) are both involved in the regulation of fetoplacental circulation in human pregnancy. The aim of this study was to investigate the effect of maternal NO supplementation in pregnancies complicated by intrauterine growth retardation (IUGR) on maternal and fetal NO and AM concentrations and their correlation with uteroplacental and fetal blood flow. We studied 20 pregnant women with IUGR and impaired uteroplacental blood flow between 27 and 35 weeks of gestation randomly selected to receive either transdermal glyceryl trinitrate or placebo. Maternal NO metabolites (NOx) and AM concentrations did not change before and after NO treatment. AM levels were significantly higher in growth retarded fetuses whose mothers received NO donors (114.1 +/- 17.6 pg/ml) than in untreated fetuses (59.8 +/- 38.6 pg/ml), whereas NO treatment did not affect significantly fetal NOx levels. Fetal AM correlated with middle cerebral artery pulsatility index in untreated IUGR but not in NO treated pregnancies.