BACKGROUNDPrenatal diagnoses are extremely advantageous for pregnant women with high-risk indicators and can help prevent the birth of malformed infants. However, no large-scale statistical study analyzing the correlation between fetal chromosome disorders and abnormal indicators during pregnancy has been done in China. The objectives of this study were to diagnose and analyze fetal chromosome abnormalities, determine the feasibility of the various prenatal test methods and establish diagnostic guidelines for the early, middle, and late trimesters.

METHODSFrom January 2004 to May 2009, 2782 pregnant women at high-risk underwent prenatal diagnoses. Categorized data expressed as either actual counts or percentages were analyzed by the chi-square or Fisher's exact test. Chorionic villus sampling was performed in the early-trimester (10 - 12 weeks of gestation), amniocentesis in mid-trimester (16 - 28 weeks of gestation), and umbilical cord blood collection in mid- or late-trimester (16 - 37 weeks of gestation). In 51 cases either autopsy samples from intrauterine fetal deaths or placental tissues from aborted fetuses were tested.

RESULTSChromosomal abnormalities were observed in 3.99% (111/2782) of the samples. Overall, the success rate of cytogenetic analysis for high-risk pregnancy groups was 98.17% (2731/2782). It was significantly less successful when used to analyze data from the chorionic villus sampling compared with that from amniocentesis and umbilical cord blood (P = 0.000). Abnormal chromosome carriers had the highest percentage of abnormal chromosomes (67.86%) when compared with chromosomal abnormalities in patients with ultra-sonographic "soft markers" (11.81%), advanced maternal age (4.51%) and those who had positive serum screening results (P = 0.000).

CONCLUSIONSInvasive prenatal diagnostic techniques are feasible tools for confirming fetal chromosomal abnormalities. Abnormal chromosomes detected in one of the parents carrying abnormal chromosome, ultrasound soft markers, advanced maternal age or positive serum screening results were associated with a higher frequency of fetal genetic diseases.