First trimester scan
Fetal genetic screening is a test performed at 11-13 weeks of pregnancy that can identify more than 85% of babies with Down syndrome and trisomy 18. The screening involves
- Ultrasonographic measurement of nuchal translucency (a skin fold behind the neck). A positive result is not diagnostic but indicates that an increased risk for a problem exists and that additional testing should be considered.
- Chorionic villous sampling in week 13 which is taking a sample of the chorionic villi of the placenta for genetic analysis under the guidance of ultrasound machines for safety.
Second trimester scan
It is a test performed at 14-17 weeks of pregnancy that can identify more than 85% of genetic abnormalities. The screening involves
- Biochemical analysis of maternal serum levels of beta-hCG (From the placenta), Free Estriol (From the fetus and placenta) and alphafeto protein (From the fetus)
- Ultrasound anomaly scan at 18-21 weeks
- Amniocentesis: It is performed at 16-20 weeks and it consists of a study of amniotic fluid after taking a sample of it by an aspiration needle guided through the abdomen by ultrasound to choose the safest and best location for aspiration.
Scientific Update (October 2026)
This chapter was first published in 2018 as part of the Prenatal Care Book, and has been reviewed and updated according to the latest guidelines. Key updates:
- First-trimester combined screening (nuchal translucency plus blood tests) detects about 85–90% of Down syndrome cases.
- Cell-free fetal DNA testing in the mother’s blood (NIPT) is available from 10 weeks and detects over 99% of Down syndrome cases, but it is a screening test and positive results must be confirmed by an invasive test.
- The miscarriage risk from CVS or amniocentesis is below 0.5% in specialist centres, and samples are now analysed with chromosomal microarray.
References: RCOG Green-top Guidelines, NICE antenatal care (NG201).
International Guidelines
In line with global standards, Dr. Sabry follows the latest recommendations from the American Society for Reproductive Medicine (ASRM), European Society of Human Reproduction and Embryology (ESHRE), and Royal College of Obstetricians and Gynaecologists (RCOG). Thus, patients receive care that is safe, ethical, and evidence-based.
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Why Choose Dr. Ashraf Sabry?
Dr. Ashraf Sabry, consultant in obstetrics, gynecology, fertility, and aesthetic gynecology, is recognized among the best OBGYN and fertility specialists in Cairo. With over 20 years of experience, he combines science and compassion to provide world-class care. Book your appointment now through the contact page here or Whatsapp us or call us on +201022224442