[Study of placenta blood flow throughout pregnancy]

The human placenta has a double vascularization which provides with two different blood flows: the uteroplacental and fetoplacental or umbilical ones. Gestational success depends on its adequate interrelationship. Uteroplacental blood flow experiences a progressive increase during gestation, being at term 17 to 20-fold that of non-pregnant uterus (600 ml/min). There are two periods of greater increase: placentation and the last part of gestation. Umbilical blood flow increases in parallel with fetal weight. Uteroplacental and umbilical blood flows are influenced by nervous, chemical and mechanical factors, but the main determinant are the vascular changes which include histological and growing and development phenomena.