Genetic counseling, prenatal screening and diagnosis of Down syndrome in the second trimester in women of advanced maternal age: a prospective study

Abstract

Background The incidence of autosomal trisomy in livebirths is strongly dependent on maternal age. Special consideration is given to the provision of prenatal screening and cytogenetic testing to women of advanced maternal age (AMA). The aim of this study was to evaluate the effectiveness of second trimester prenatal screening and amniocentesis for Down syndrome (DS) and compare the trends of choice of screening and amniocentesis among AMA women. Methods A total of 5404 AMA patients with natural singleton pregnancy were recruited for this prospective study from January 2008 to December 2010. The gestational weeks were from 15 weeks to 20+6 weeks. The patients referred were grouped into a screening group (2107 cases) and an amniocentesis group (3297 cases) by their own decision. The prevalence of DS was compared between the two groups by chi-square test. Choice rates for each maternal age with trends were compared by regression analysis. Results There were 18 cases of fetal DS detected in the screening group with a prevalence of 8.54‰ (18/2107). Twenty-five cases of fetal DS were diagnosed in the amniocentesis group with a prevalence of 7.58‰ (25/3297). No statistical difference was observed in the prevalence of DS between the screening and amniocentesis group (P=0.928). The invasive testing rate for DS in the amniocentesis group was 5.54 times higher than that of the screening group (1/131.88 vs. 1/23.78). With the increase of the maternal age, the choice of amniocentesis increased while the choice of the screening showed an opposite trend. The choice of the AMA women between the screening and amniocentesis was significantly age relevant (P=0.012). Conclusions The second trimester serum screening in combination with maternal age was more effective than maternal age alone to screen for DS. We suggest educating the patients by recommending AMA women be informed of both screening and amniocentesis options.