To evaluate whether maternal and fetal plasma adrenomedullin levels in pregnancies with small for gestational age (SGA) infants are different from those in pregnancies with appropriate for gestational age (AGA) infants. Maternal and fetal circulating adrenomedullin levels were compared between 62 pregnancies with AGA (43 delivered vaginally and 19 delivered by elective cesarean section) and 28 pregnancies with SGA (20 delivered vaginally and 8 delivered by elective cesarean section) at birth. Plasma adrenomedullin levels were measured from maternal and cord venous blood samples using a radioimmunoassay. Umbilical artery blood pH was also measured. There were no significant differences for maternal total adrenomedullin levels, mature adrenomedullin levels, and its ratio among the groups. There were also no significant differences for fetal total adrenomedullin levels, mature adrenomedullin levels, and its ratio among the groups. In the AGA group delivered vaginally, fetal mature/total adrenomedullin ratio (mean ± standard error, 16.6 ± 0.7%) was significantly higher than the maternal ratio (13.8 ± 0.6%) (p < 0.05). In the SGA group delivered vaginally, fetal mature/total adrenomedullin ratio (18.5 ± 1.0%) was also significantly higher than the maternal ratio (14.5 ± 0.6%) (p < 0.05). There was no significant difference in umbilical artery blood pH among the groups. Conclusions. These results suggest that maternal and fetal plasma circulating adrenomedullin levels may play a role in maternal and fetal cardiovascular adaptation during delivery in pregnancies with both AGA and SGA infants.