RESEARCH RATE OF ABNORMAL CHROMOSOME BY AMNIOTIC CELL CULTURE FROM AMNIOCENTESIS IN PREGNANCY WOMEN IN NATIONAL OBSTETRIC GYNECOLOGY HOSPITAL AND IN HANOI OBSTETRIC GYNECOLOGY HOSPITAL FROM 1/2008 TO 6/2009 Descriptive study on 438 women who had aspiration of amniotic fluid for analysis to detect chromosomal abnormalities in National Obstetric and Gynecology Hospital and in Hanoi Obstetric and Gynecology Hospital period from 1/1/2008 30/6/2009.