Background: The placenta is the base for the exchange of nutrients, oxygen and waste products for the fetus. The placental vessels hold a crucial role in regulation the blood flow, and a compromised placental function leads to serious complications such as fetal death or growth retardation. An in-depth understanding of the mechanism regulating blood flow and perfusion is necessary if we are to come up with new ideas for intervention and treatment. Method: From fresh born placentas stem villi arteries were carefully dissected. The artery branches were divided. The surrounding tissue was removed from one end and was left untouched in the other end. Then using wire myography they were investigated in terms of contractility and sensitivity to physiological relevant human-like agonists. Results: Sensitivity to PGF2α, Tx-analog, 5-HT and endothelin-1 was significantly lower in arteries with intact surrounding tissue compared to arteries stripped of the tissue. The maximal force development was also significantly lower in arteries with surrounding tissue, when they were depolarized high extracellular [K+] or stimulated with PGF2α or endotheline-1. Conclusion: The perivascular tissue significantly alters stem villi arteries’ sensitivity and force development in a suppressive way. This implicates a new aspect of blood flow regulation in the placenta.