Screening for Down Syndrome Using Nuchal Translucency Thickness and Nasal Bone Examination at Advanced Maternal Age in Jakarta: A Preliminary Report

Abstract

Older maternal age leads to increased risk for both the mother and fetus, particularly if the mother is more than 34 years old. We evaluated a non-invasive method to screen for Down syndrome at a maternal age of 35 years or more. We measured nuchal translucency thickness (NT) using a fixed cut-off of 3.0 mm or more with a crown-rump length (CRL) of 50-70 mm and nasal bone (NB) examination at 11-13+6 weeks of gestation. This prospective study was conducted from January 2001 to January 2003. NT was measured at 11-13+6 weeks of gestation. In addition, the NB was examined from January 2002 to January 2003. Cases with an NT of at least 3.0 mm were submitted to TORCH examination (toxoplasma, rubella, cytomegalovirus, and herpes simplex virus I and II). Genetic amniocentesis was performed at 16 weeks of gestation. Both antenatal and postnatal management and observations were carried out. NT was measured in 175 cases between January 2001 and January 2002. Combined NT measurement and NB examination was performed in 97 cases between January 2002 and January 2003. Maternal ages ranged from 35 to 43 years, with first to fifth gravidity. Of the 175 NT cases, seven had NT of at least 3.0 mm. The detection rate (DR) for Down syndrome was 71.4% (5/7) and the false-positive rate (FPR) was 1.2% (2/170). Of the 97 NT plus NB absence cases, four had an NT of at least 3.0 mm and three had no NB. The combination of maternal age, NT and NB examination gives a DR for Down syndrome of 87.5% (3/4 paralleled to 3/3) and an FPR of 1% (1/94). Screening for Down syndrome can be performed in the clinical setting by measuring NT (using a fixed cut-off of ≥3.0 mm and CRL of 50-70 mm) and NB examination at 11-13+6 weeks of gestation. Abnormal NT with normal karyotype requires strict antenatal and postnatal observation.