Topological factors in placental surface arteries correlate with neonatal birth weight. 
There has been no study concerning association between topological factors of placental vascularization and neonatal growth in humans.  The aim of study was to assess whether any network index of placental surface arteries was associated with neonatal birth weight.  Twenty-six placentas were randomly selected between 34 and 41 weeks of gestational ages.  Placental weights ranged 385 to 770 g; and neonatal weights ranged 1960 to 3680 g. After visualization of placental surface arteries by a milk injection method, network indices including the number of nodes, network density, network diameter, average distance of nodes, and the degree centralization were determined.  These network indices and placental weights were compared with neonatal birth weights.  The number of nodes, network density, network diameter, average distance of nodes, and the degree centralization were found to be as follows (Mean +/- SD); 84.7 +/- 29.3, 0.0262 +/- 0.0088, 15.8 +/- 2.77, 7.83 +/- 1.13, 0.0263 +/- 0.0091, respectively.  We found that neonatal birth weights correlated with the number of nodes of placental surface arteries (correlation coefficient R = 0.40) and placental weights (R = 0.52) both.  However, the number of nodes of placental surface arteries was not associated with the placental weights or the gestational age.  We for the first time found that a topological factor, i.e., the number of nodes of placental surface arteries correlated with neonatal growth.  There was no correlation between numbers of nodes and placental weights.  This suggests that the number of nodes affects fetal growth independent of placental weights.  A topological factor of placental vascularization might significantly affect fetal growth in utero and determine risks of vascular diseases in their future lives.