Examinations of 121 late reproductive-aged pregnant women and 71 women younger than 35 years established differences in the values of uterine artery blood flow and volumetric placental circulation in the first trimester of pregnancy. The median pulsatility index (PI) gradually reduced from 11 to 14 weeks, with a fetal coccygeoparietal size of 45 to 84 mm in the examined groups. Higher PIs were observed in the group of late reproductive-aged women throughout the first trimester. ROC analysis demonstrated that the uterine artery PI with an optimal threshold of over 1.58 and the volumetric blood flow index FI with that of below 29.39 are of the great prognostic value. It is expedient to use the findings in clinical practice to assess the quality of fetoplacental system formation.