title: [Analysis of the combined first trimester screening for chromosomal abnormalities].
abstract: OBJECTIVE
  to evaluate the performance of the combined first trimester screening for chromosomal abnormalities in a group of the Brazilian population.
  
  
  METHODS
  a retrospective study including pregnant women with single fetuses referred to a fetal medicine center to perform the first trimester screening that combines maternal age, nuchal translucency measurement and two maternal serum biochemical markers: free B-hCG and PAPP-A. To evaluate the performance of the test, the detection rate, specificity, negative and positive predicted values and false-positive rates were calculated, considering as high risk the cut-off value above 1 in 300.
  
  
  RESULTS
  we studied 456 patients submitted to the test. Advanced maternal age above 35 years was observed in 36.2% of cases. The incidence of chromosomal abnormalities in the study population was 2.2%. Twenty-one patients (4.6%) presented a high risk (above 1:300) by the combined test. Using this cut-off level, the detection rate of the test was 70% for all chromosomal abnormalities and 83.3% for trisomy 21, for a false-positive rate of 3.1%.
  
  
  CONCLUSIONS
  the combined first trimester screening was effective to detect chromosomal abnormalities, mainly for trisomy 21, with low false-positive rates. The combined test contributed to decreasing the indication of an invasive test if we compare to maternal age alone as a risk factor.
authors.affiliation: Setor de Medicina Fetal do Hospital Albert Einstein-São Paulo (SP), Brasil.
authors.forename: Carolina Leite
authors.initials: CL
authors.lastname: Drummond
authors.forename: Rita de Cássia Sanches
authors.initials: Rde C
authors.lastname: Oliveira
authors.forename: Luiz Claudio de Silva
authors.initials: LC
authors.lastname: Bussamra
authors.forename: Cristóvão Luis P
authors.initials: CL
authors.lastname: Mangueira
authors.forename: Eduardo
authors.initials: E
authors.lastname: Cordioli
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Aoki
mesh_terms: D000328:Adult; D025063:Chromosome Disorders / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011296:Prenatal Diagnosis; D012189:Retrospective Studies; D055815:Young Adult