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Objectives To assess the effectiveness of combined ultrasound and biochemical (CUB) screening for chromosome abnormalities in singleton pregnancies in a routine antenatal clinic and laboratory setting. Methods Women whose pregnancies fell within the gestational age range of 11 to 14 weeks by ultrasound assessment were offered CUB screening on the basis of measurement of nuchal translucency (NT), maternal serum free beta-human chorionic gonadotrophin (FβhCG) and pregnancy-associated plasma protein A (PAPP-A). NT measurements were obtained using a standardised method defined by the Fetal Medicine Foundation and FβhCG, and PAPP-A were measured using the DELFIA immunoassay system. Each screening marker measurement was converted to a multiple of the appropriate gestational median and a risk was derived using previously published parameters for each marker in chromosomally abnormal and unaffected pregnancies. A combined risk of Down syndrome and of trisomy 18/13, incorporating the maternal age risk, was calculated for all women. Invasive diagnostic testing was offered to women whose combined risk exceeded the cut-off risk of 1 in 250 (term). Results Five thousand and eighty-four women accepted a first-trimester screening test for Down syndrome, representing 75% of the eligible booking population. Out of the population eligible for CUB screening at the time of booking, NT measurements were obtained from 93% at the first clinic visit and 7% had to return for a second attempt. After excluding women who defaulted on a return visit, satisfactory NT measurements were obtained in 99.5% of pregnancies. Fifteen cases of Down syndrome and eleven pregnancies with other chromosome abnormalities were ascertained. The detection rate for Down syndrome was 93% (14/15) at a false-positive rate of 5.9% and for all chromosome abnormalities it was 96% (25/26) at an overall false-positive rate of 6.3%. Conclusions CUB screening offers a significant improvement in sensitivity over second-trimester biochemical screening and is deliverable within a routine prenatal clinical setting. Copyright © 2004 John Wiley & Sons, Ltd.

Objectives: Nuchal translucency is known to be a sonographic marker of autosomal trisomy. First trimester screening for Down’s syndrome has been offered routinely since August 2000 in the Queen Mother’s Hospital. The screening programme involves measurement of maternal serum for free bhCG and PAPP-A and nuchal translucency (NT) between 11–14 weeks of gestation. Nuchal translucency is known to be a sonographic marker of autosomal trisomy. Nuchal translucency measurements need to be precise, accurate and reproducible when being used as part of a screening programme. A system of audit is therefore required to ensure that the operators carrying out these measurements are doing so to appropriate standards. Methods: A hard copy thermal image was saved from each nuchal translucency measurement taken. A scoring system was used to score the images. 10 random images from each operator were reviewed each month and scored by an independent assessor. In addition individual NT MOM (multiple of median) values were compared statistically. Scores were given to each operator for inter-operator agreement of the 95% and 99% confidence intervals. These scores and those from the assessment of images were combined to give results, which were given to each operator along with comments on how to improve the images. Results: Changes in the measurement of NT were assessed over a four-month period using the Mann-Whitney test for comparisons between groups of two operators. There was a significant difference between operator 1 and operator 2 in the first month (p = 0.001) but by the fourth month there was no significant difference (p = 0.858). Conclusions: The quality control cycle aids the improvement of NT images and reduces inter-operator variation.