Beginning at very low concentrations (0.001 g/100 ml), alcohol elicited dose‐dependent contractions of the human umbilical artery in vitro. Additionally, 16 of the 108 arteries tested had a 5‐10‐min spasm in response to alcohol. Alcohol (0.2 91100 ml) also increased tension developed in response to all angiotensin II doses, but had no effect on serotonin‐induced contractions. These results suggest that alcohol may increase umbilicoplacental resistance in vivo, thus decreasing fetal‐placental b