One-stop clinic for assessment of risk for trisomy 21 at 11-14 weeks: a prospective study of 15 030 pregnancies.
OBJECTIVE
To evaluate the performance of a one-stop clinic for assessment of risk (OSCAR) for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free beta-human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11-14 weeks of gestation.


METHODS
Screening for trisomy 21 was carried out by OSCAR in 15 030 singleton pregnancies with live fetuses at 11-14 weeks. The estimated risk for trisomy 21 was calculated, and the women were counseled regarding this risk and the option of invasive testing or expectant management. Follow-up of the outcome of all pregnancies was carried out. The detection and false-positive rates for different risk cut-offs were calculated.


RESULTS
Fetal NT and maternal serum free beta-hCG and PAPP-A were successfully measured in all cases. Pregnancy outcome, including karyotype results or the birth of a phenotypically normal baby, was obtained from 14 383 cases. The median maternal age of these cases was 34 (range 15-49) years and in 6768 (47.1%) the age was 35 years or greater. The median gestation at screening was 12 (range 11-14) weeks and the median fetal crown-rump length was 64 (range 45-84) mm. The estimated risk for trisomy 21 based on maternal age, fetal NT and maternal serum free beta-hCG and PAPP-A was 1 in 300 or greater in 6.8% (967 of 14 240) normal pregnancies, in 91.5% (75 of 82) of those with trisomy 21 and in 88.5% (54 of 61) of those with other chromosomal defects. For a fixed false-positive rate of 5% the respective detection rates of screening for trisomy 21 by maternal age alone, maternal age and serum free beta-hCG and PAPP-A, maternal age and fetal NT, and by maternal age, fetal NT and maternal serum biochemistry were 30.5%, 59.8%, 79.3% and 90.2%, respectively.


CONCLUSIONS
Screening for trisomy 21 by a combination of maternal age, fetal NT and maternal serum biochemistry at 11-14 weeks can be provided in an OSCAR setting and is associated with a detection rate of about 90% for a false-positive rate of 5%.
Bindra
R
R
Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
Heath
V
V
Liao
A
A
Spencer
K
K
Nicolaides
K H
KH
D000328:Adult; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000032:analysis; D004314:Down Syndrome / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D005865:Gestational Age; D006801:Humans; D008403:Mass Screening; D008423:Maternal Age; D011247:Pregnancy; D011256:Pregnancy Outcome; D018566:Pregnancy, High-Risk; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D011446:Prospective Studies; D018570:Risk Assessment
D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A