Reference Centile Chart for Fetal Nuchal Translucency, Maternal Serum PAPP-A and Free Beta hCG
Saifon Chawanpaiboon MD*, Prakong Cheunwattana BSc**
Affiliation : * Division of Maternal-Fetal Medicine, Department of Obstetrics & Gynecology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand ** Division of Obstetrics and Gynecology Nursing, Department of Obstetrics & Gynecology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
Objective : To create reference centile chart of fetal nuchal translucency, maternal serum pregnancy associated
plasma protein-A (PAPP-A) and maternal serum free beta human chorionic gonadotropin (beta-hCG) in
order to predict preliminarily Down syndrome in Thai fetuses during 10-14 weeks of gestation.
Material and Method: This was a prospective, descriptive cohort study. From 1 January 2004 to 31 December,
2006, a total of 1,000 pregnant women during 10-14 weeks of gestation were participated in the present study.
Pregnancy outcomes were reviewed from the records. The excluded cases were chromosomal and major
structural abnormalities, twin pregnancy and cases resulting in miscarriage or intrauterine death. All women
had a scan for nuchal translucency (NT) and had blood taken for measurement of maternal serum PAPP-A and
free beta-hCG level.
Results : The mean NT was 1.6 + 0.8 mm (range 0.3-14 mm). The 5th, 50th and 95th centile of PAPP-A and free
beta-hCG during 11-14 weeks of gestation were 1.54-69, 14-28, 51-57 and 24.8-17, 78-47, 181.6-126.5 mIU/
mL, respectively. The distribution and the 5% and 95%, lower and upper limits of NT, PAPP-A and free beta-
hCG was presented.
Conclusion : The present study shows that NT measurements increase with increasing gestational age. The
mean serum PAPP-A rises and the mean serum-free beta hCG decreases from 10 to 14 weeks of gestation in
normal Thai fetuses. These results can be used for reference value to predict fetal Down Syndrome.
Keywords : Nuchal translucency, Pregnancy associated plasma protein-A, PAPP-A, Serum free beta human chorionic gonadotropin, Free beta-hCG, Reference centile chart
