Retrospective study on the effects of gestational week and maternal age on screening of Down's syndrome

Objective: To explore the effects of gestational week and maternal age on screening of Down's syndrome. Methods: The detection results of serum markers in pregnant women who received prenatal screening during the second trimester of pregnancy in Tianjin city in 2010 were analyzed retrospectively,the results of amniotic fluid cell chromosomal examination in pregnant women with high risk of trisomy 21 were traced,the false positive rates of Down's syndrome were compared among different gestational weeks in pregnant women in the same age group,the high risk rates of Down's syndrome screening among pregnant women in different age groups were also compared. Results: Among 84 401 pregnant women,3 652 pregnant women were found with high risk of Down's syndrome,and 13 pregnant women were diagnosed as Down's syndrome definitely,the false positive rate of screening was 4. 31%,the false positive rate of screening in pregnant women of 17- 18+ 6gestational weeks was less than 4%( 3. 85%- 3. 98%),which was statistically significantly lower than those in pregnant women of 15- 16+ 6gestational weeks and 19- 20+ 6gestational weeks( P 0. 05); there was statistically significant difference in the high risk rate of Down's syndrome among pregnant women in different age groups( P 0. 01). Conclusion: Serological screening and prenatal diagnostic techniques can effectively detect the fetuses with Down 's syndrome before delivery,reduce the birth rate of infants with Down' s syndrome; in order to improve the detection rate of Down's syndrome,the ideal gestational weeks to conduct prenatal screening are 17- 18+ 6gestational weeks.