Effective screening for major aneuploidies can be provided in the first trimester of pregnancy. Screening by a combination of fetal nuchal translucency and maternal serum free-β-human chorionic gonadotrophin and pregnancy-associated plasma protein-A can identify about 90% of fetuses with trisomy 21 and other major aneuploidies for a false-positive rate of 5%. Improvement in the performance of first-trimester screening can be achieved by firstly, inclusion in the ultrasound examination assessment of the nasal bone and flow in the ductus venosus, hepatic artery and across the tricuspid valve, and secondly, carrying out the biochemical test at 9 to 10 weeks and the ultrasound scan at 12 weeks.

https://obgyn.onlinelibrary.wiley.com/doi/epdf/10.1002/pd.2637

Screening for fetal aneuploidies at 11 to 13 weeks

Development of prenatal screening—A historical overview

In the nearly 60 years since prenatal diagnosis for genetic disease was first offered, the field of prenatal diagnosis has progressed far past rudimentary uterine puncture to provide fetal material to assess gender and interpret risk. Concurrent with the improvements in invasive fetal sampling came technological advances in cytogenetics and molecular biology that widened both the scope of genetic disorders that could be diagnosed and also the resolution at which the human genome could be interrogated. Nowadays, routine blood work available to all pregnant women can determine the risk for common chromosome abnormalities; chorionic villus sampling (CVS) and amniocentesis can be used to diagnose nearly all conditions with a known genetic cause; and the genome and/or exome of a fetus with multiple anomalies can be sequenced in an attempt to determine the underlying etiology. This chapter will discuss some of the major advances in prenatal sampling and prenatal diagnostic laboratory techniques that have occurred over the past six decades.

Traditional Prenatal Diagnosis: Past to Present.

Objective: To assess the incidence of nasal hypoplasia among fetuses of southern Chinese women. Methods: This prospective observational study was conducted at Pri

Nasal Bone Hypoplasia: Is It a Common Finding amongst Chromosomally Normal Fetuses of Southern Chinese Women?

We assessed the discriminatory efficiency and cost-effectiveness of a novel way of organising first trimester screening for Down syndrome (DS), contingent testing, where a serological test (PAPP-A and beta-hCG: the double test) is made in early first trimester and followed by nuchal translucency testing (NT) only in women with an intermediate risk, e.g. 1:1000, and not in all women as in normal first trimester screening (NFTS). Using Monte Carlo simulation contingent testing had a detection rate (DR) of 78.9% and a false-positive rate (FPR) of 4.0% for DS with 19.4% of women offered NT testing. The DR of NFTS was 85.5% and the FPR 4.4%. The decrease in NT screening was associated with an increase from 23% to 29% in the proportion of DS cases born. The cost of the contingent testing programme was pound 53,000 per DS case not born and pound 91,000 in NFTS. The number of aborted fetuses per DS case were 0.35 and 0.36, respectively. Thus, contingent testing is an organisation of first trimester screening where costs can be reduced with a marginal decrease in performance. Contingent testing is attractive in areas where NT screening is the bottleneck preventing the introduction of first trimester screening.

An increase in cost-effectiveness of first trimester maternal screening programmes for fetal chromosome anomalies is obtained by contingent testing.

Correct estimation of parameters for ultrasound nuchal translucency screening - Authors' reply

Maternal serum alphafetoprotein screening for open neural tube defects: revised statistical parameters.

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Correct estimation of parameters for ultrasound nuchal translucency screening - Authors' reply

Maternal serum alphafetoprotein screening for open neural tube defects: revised statistical parameters.