Centro Nacional de Genética Médica. Habana, Cuba. Cytogenetic Prenatal Diagnosis in Cuba. Causes of low prevalence of Down syndrome. Luis A. Méndez Rosado*, Ursulina Suarez, Minerva García, Anduriña Barrios Martínez, Enny Morales Rodríguez, Michel Soriano, Arlay Castelvil, Yomisleydi Bravo, Odalys Molina, Nereida González, Luanda Maceiras. Centro Nacional de Genética Médica. Habana, Cuba. * albermen@infomed.sld.cu RESULTS ABSTRACT Chromosome aberrations detected by each laboratory (amniotic fluid and chorionic villus sampling) and continued pregnancies Diagnósis a NCMG Santiago Cuba Villa Clara Holguín Camagüey Pinar Río Ciego Ávila RGC Cienfuegos Granma Santi Spiritus Matanzas Total Continued pregnancies Trisomía 21 288 109 107 48 61 23 49 19 45 31 22 825 29 Trisomía 18 73 32 8 5 2 16 9 7 199 1 Trisomía 13 21 - 4 76 45,X 6 3 83 47,XXX 20 13 14 69 47,XXY 11 47,XYY Otras anomalías 118 47 55 57 42 10 12 406   124 568 256 234 137 131 41 39 79 62 1746 201 Objectives: To analyze trends in cytogenetic prenatal diagnosis in Cuba and to analyze possible causes leading to a low Down syndrome prevalence in a country where the maternal serum biochemical markers (triple test) is not available. Methods: An analysis of the Cuban program in prenatal cytogenetic diagnosis from 1984 to 2012 was conducted. Results are described, with particular emphasis on indications, abnormal results, types of invasive procedures, and terminations of pregnancy. Results: Cytogenetic prenatal diagnostic analyses (n=75 095) were conducted; maternal age was the indication for 77.9% of the amniocenteses and chorionic villus samplings. The detection rate of chromosomally abnormal pregnancies was 2.3% for maternal age and increased to 8–9% for other indications. When a chromosomal abnormality was identified, 88.5% terminated the pregnancy. In 2002, the live birth prevalence of Down syndrome was 8.4 per 10 000 live births, and in 2012, 7 per 10 000. Conclusion: Prenatal diagnosis in Cuba has contributed to a significant reduction in chromosomal aberrations. The impact increased because of the demographic trends of the population, the high index of terminations of pregnancy, and the establishment of a network of cytogenetic laboratories throughout Cuba. RGC, Ramón González Coro Hospital; NCMG, National Center of Medical Genetic. a Cases of chromosome mosaicism were included. 88,5% terminated the pregnancy INTRODUCTION Cytogenetic prenatal diagnosis (CPD) is a reliable option for couples with a high risk of conceiving children with chromosomal abnormalities. The national program for diagnosis, management, and prevention of genetic diseases and congenital anomalies started in Havana at the beginning of the 1980s. The spread of CPD in Cuba occurred in two stages: the establishment of laboratories located in the Cuban provinces of Havana, Santiago de Cuba, Villa Clara, Matanzas, Camagüey, and Holguín, and in 2004, seven laboratories in other provinces of the country were inaugurated. The present study describes a large population in a developing country undergoing cytogenetic prenatal diagnoses from 1984 to 2012. In the present study, the CPD in Cuba is evaluated as well as the factors contributing to the low prevalence of Down syndrome and other chromosomal anomalies in a country where the triple test in maternal blood is not available. METHODS A cross-sectional study of the Cuban CPD procedures from 1984 to 2012 was conducted, composed of information from prenatal cytogenetic publications based on the Cuban population, PhD thesis, and the databases of 12 of the 14 cytogenetic laboratories in Cuba Data included number of prenatal diagnosis undertaken, reasons for referral to the laboratory, number and kind of chromosomal anomalies, and percentage of pregnant women who continued their pregnancy despite an abnormal prenatal diagnosis. Data retrieved from the Cuban Registry of Congenital Malformations were used to measure the impact of the CPD program in Cuba as well as the Down syndrome detected stratified by age (two groups 20–29 and 35–44 years of age) in the 2007–2012 period. The database from Oficina Nacional de Estadísticas de Salud, Ministerio de Salud Pública de Cuba was used to determine the total number of live births between 1989 and 2012 and the distribution of all birth in two maternal age groups, from 20 to 29 years and from 35 to 44 years DS, Down syndrome REFERENCE Heredero-Baute L. Community-based program for the diagnosis and prevention of genetic disorders in Cuba. Twenty years of experience. Community Genet 2004;7(2-3):130–6. Méndez-Rosado LA, Hechavarría-Estenoz D, de la Torre ME et al. Current status of prenatal diagnosis in Cuba: causes of low prevalence of Down syndrome. Prenatal Diagnosis 2014, 34:1–6.