Prevalence of Abnormal Prenatal Screening for Down Syndrome in Udonthani Hospital Using Nuchal Translucency and Biochemical Marker

Abstract

Background : Down syndrome  is the most common  genetic  cause of mental  retardation  . Prenatal  screening  test could be useful  for  early  detection  and   provides the chance  for  termination  of  pregnancy  or  prepare  the  family  to  take care of their baby.

^{Objective : To  study  the prevalence  of  positive  results of  prenatal  screening  for Down syndrome  using  Nuchal  translucency  and  biochemical  test  in  Udonthani  hospital.}

Design : A  descriptive  study.

Setting : Antenatal  care  clinic , Department  of  Obstetrics  and Gynecology  ,Udonthani  hospital  ,Udonthani.

Subjects : Pregnant  women   who  had  their  antenatal  care  at  Udonthani  Hospital  from  January  2005  to  December  2007

Materials and Methods : Prenatal  screening test  for Down syndrome  were performed in  314  pregnant  women   composed  of  123  cases of  Nuchal  translucency  measurement  at 10-13 weeks of gestation  and  biochemical  tests ( using   PAPP-A   plus  Free  beta hCG   at  10-14  weeks  of  gestation  or Maternal  serum  Alpha fetoprotein  plus  Free  beta hCG   between 15-20  weeks )  and  biochemical  tests only  in  191 cases . Gestational  ages  were  determined  by  ultrasonographic  parameters   . Genetic  amniocentesis  were  offered  to  women  with  Nuchal  translucency  equal  or  more than  3   or  calculated  down  syndrome  risk  of 1 :270 or greater  and  to  women  aged  35  years  or  over

Babies  data  were  followed  after  birth  in both screening  and  non  screening  group .

Results : Prevalence  of  positive  screening  tests  were   9.6 %  (30/314)  composed of  Nuchal  translucency  more  than or equal  to   3 mms   2.4 % ( 3 /123)   and   8.9 % (28/314)  of  abnormal  biochemical test  ( risk greater  than or equal to 270 )  .  All  of  positive  screening  test  were  received   genetic  amniocentesis   and  1 case (3.3 %) of  trisomy 21 was detected  ,  All  of  negative  screening  cases  wered  followed  and  1  case  of  trisomy  21  was found (in  low risk group) . Detection rate  of our screening  test  is 50 % and  false positive rate  is 9.3 %

Conclusion : Maternal  screening  using  nuchal  translucency  and  biochemical  test   is  effective  in the detection  of  fetal  down syndrome and  possibly  one  chioce  for   pregnant  women  especially  in low risk group.