The authors present their experience in implementing the national project "Prenatal diagnosis of developmental abnormalities in a baby" in one of the pilot area of the Moscow Region (MR) and the results of carrying out a package of measures of mass integrated prenatal screening to identify chromosomal abnormalities, such as trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau's syndrome), and congenital developmental defects in the fetus in the first trimester of pregnancy (at weeks 11 to 14). The efficiency of prenatal screening in the MR in the analyzed period November 2010 to December 2011 was evaluated in the second half of 2012 after receiving all information on the outcomes of pregnancy and labor in women undergoing prenatal screening during the first trimester. The analysis was made with consideration for the data of the regional fetal and neonatal congenital anomaly register. The examined indicators of early screening efficiency were included the percentage of pregnant women covered with the new screening program, the values of the sensitivity and specificity of an introduced algorithm, the proportion of false-positive and false-negative results, and the audit of ultrasound and biochemical studies. According to the results of prenatal screening, a high-risk group included 665 (an individual risk level of 1:100) of 50 753 screened women. There were 470 invasive procedures: 282 (60%) chorionic villus aspirations and 188 (40%) amniocenteses with a laboratory genetic examination of fetal specimens. Postabortion specimens were examined in 33 cases. One hundred and seventy-seven fetuses with chromosomal abnormalities were identified; 266 cases were diagnosed with congenital malformations; of them 102 cases were life-threatening.