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Screening for Down syndrome based on maternal age or fetal nuchal translucency: a randomized controlled trial in 39572 pregnancies

Saltvedt, S; Almstrom, H; Kublickas, M; Valentin, Lil LU ; Bottinga, R; Bui, TH; Cederholm, M; Conner, P; Dannberg, B and Malcus, Peter LU , et al. (2005) In Ultrasound in Obstetrics & Gynecology 25(6). p.537-545
Abstract
Objectives Nuchal translucency (NT) screening increases antenatal detection of Down syndrome (DS) compared to maternal age-based screening. We wanted to determine if a change in policy for prenatal diagnosis would result in fewer babies born with DS. Methods A total of 39572 pregnant women were randomized to a scan at 12-14 gestational weeks including NT screening for DS (12-week group) or to a scan at 15-20 weeks with screening for DS based on maternal age (18-week group). Fetal karyotyping was offered if risk according to NT was >= 1 :250 in the 12-week group and if maternal age was >= 35 years in the 18-week group. Both policies included the offer of karyotyping in cases of fetal anomaly detected at any scan during pregnancy or... (More)
Objectives Nuchal translucency (NT) screening increases antenatal detection of Down syndrome (DS) compared to maternal age-based screening. We wanted to determine if a change in policy for prenatal diagnosis would result in fewer babies born with DS. Methods A total of 39572 pregnant women were randomized to a scan at 12-14 gestational weeks including NT screening for DS (12-week group) or to a scan at 15-20 weeks with screening for DS based on maternal age (18-week group). Fetal karyotyping was offered if risk according to NT was >= 1 :250 in the 12-week group and if maternal age was >= 35 years in the 18-week group. Both policies included the offer of karyotyping in cases of fetal anomaly detected at any scan during pregnancy or when there was a history of fetal chromosomal anomaly. The number of babies born with DS and the number of invasive tests for fetal karyotyping were compared. Results Ten babies with DS were born alive with the 12-week policy vs. 16 with the 18-week policy (P = 0.25). More fetuses with DS were spontaneously lost or terminated in the 12-week group (45119 796) than in the 18-week group (27119 776; P = 0.04). All women except one with an antenatal diagnosis of DS at < 22 weeks terminated the pregnancy. For each case of DS detected at < 22 weeks in a living fetus there were 16 invasive tests in the 12-week group vs. 89 in the 18-week group. NT screening detected 71% of cases of DS for a 3.5% test-positive rate whereas maternal age had the potential of detecting 58% for a test-positive rate of 18%. Conclusions The number of newborns with DS differed less than expected between pregnancies that had been screened at 12-14 weeks' gestation by NT compared with those screened at IS-20 weeks by maternal age. One explanation could be that NT screening - because it is performed early in pregnancy - results in the detection and termination of many pregnancies with a fetus with DS that would have resulted in miscarriage without intervention, and also by many cases of DS being detected because of a fetal anomaly seen on an 18-week scan. The major advantage of the 1.2-week scan policy is that many fewer invasive tests for fetal karyotyping are needed per antenatally detected case of DS. (Less)
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Contribution to journal
publication status
published
subject
keywords
prenatal diagnosis, nuchal translucency, screening, genetic, fetal ultrasonography, chromosomal disorder, Down syndrome, ultrasound
in
Ultrasound in Obstetrics & Gynecology
volume
25
issue
6
pages
537 - 545
publisher
John Wiley & Sons
external identifiers
  • pmid:15912479
  • wos:000229812000003
  • scopus:20644435133
ISSN
1469-0705
DOI
10.1002/uog.1917
language
English
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yes
id
3fd9b038-f666-4cc5-80b9-57f331ae7357 (old id 234082)
date added to LUP
2007-10-05 13:49:01
date last changed
2017-09-17 07:00:09
@article{3fd9b038-f666-4cc5-80b9-57f331ae7357,
  abstract     = {Objectives Nuchal translucency (NT) screening increases antenatal detection of Down syndrome (DS) compared to maternal age-based screening. We wanted to determine if a change in policy for prenatal diagnosis would result in fewer babies born with DS. Methods A total of 39572 pregnant women were randomized to a scan at 12-14 gestational weeks including NT screening for DS (12-week group) or to a scan at 15-20 weeks with screening for DS based on maternal age (18-week group). Fetal karyotyping was offered if risk according to NT was &gt;= 1 :250 in the 12-week group and if maternal age was &gt;= 35 years in the 18-week group. Both policies included the offer of karyotyping in cases of fetal anomaly detected at any scan during pregnancy or when there was a history of fetal chromosomal anomaly. The number of babies born with DS and the number of invasive tests for fetal karyotyping were compared. Results Ten babies with DS were born alive with the 12-week policy vs. 16 with the 18-week policy (P = 0.25). More fetuses with DS were spontaneously lost or terminated in the 12-week group (45119 796) than in the 18-week group (27119 776; P = 0.04). All women except one with an antenatal diagnosis of DS at &lt; 22 weeks terminated the pregnancy. For each case of DS detected at &lt; 22 weeks in a living fetus there were 16 invasive tests in the 12-week group vs. 89 in the 18-week group. NT screening detected 71% of cases of DS for a 3.5% test-positive rate whereas maternal age had the potential of detecting 58% for a test-positive rate of 18%. Conclusions The number of newborns with DS differed less than expected between pregnancies that had been screened at 12-14 weeks' gestation by NT compared with those screened at IS-20 weeks by maternal age. One explanation could be that NT screening - because it is performed early in pregnancy - results in the detection and termination of many pregnancies with a fetus with DS that would have resulted in miscarriage without intervention, and also by many cases of DS being detected because of a fetal anomaly seen on an 18-week scan. The major advantage of the 1.2-week scan policy is that many fewer invasive tests for fetal karyotyping are needed per antenatally detected case of DS.},
  author       = {Saltvedt, S and Almstrom, H and Kublickas, M and Valentin, Lil and Bottinga, R and Bui, TH and Cederholm, M and Conner, P and Dannberg, B and Malcus, Peter and Marsk, A and Grunewald, C},
  issn         = {1469-0705},
  keyword      = {prenatal diagnosis,nuchal translucency,screening,genetic,fetal ultrasonography,chromosomal disorder,Down syndrome,ultrasound},
  language     = {eng},
  number       = {6},
  pages        = {537--545},
  publisher    = {John Wiley & Sons},
  series       = {Ultrasound in Obstetrics & Gynecology},
  title        = {Screening for Down syndrome based on maternal age or fetal nuchal translucency: a randomized controlled trial in 39572 pregnancies},
  url          = {http://dx.doi.org/10.1002/uog.1917},
  volume       = {25},
  year         = {2005},
}