Test introduction Detection advantage Testing process For people
Technical brief


1. What is non-invasive prenatal DNA testing?

Non-invasive prenatal DNA testing is a new type of testing technique targeted at numerical abnormalities of chromosomes for fetuses. Adopting a new generation of high-throughput sequencing technology combined with bioinformatic analysis, the test helps detect and analyze cell-free DNA in pregnant women’s peripheral blood. Non-invasive prenatal DNA testing is a safe, accurate and fast testing technique. 

21-trisomy syndrome (Down's syndrome), 18-trisomy syndrome (Edwards syndrome) and 13-trisomy syndrome (Patau syndrome), all of which show high incidence currently, are covered by non-invasive prenatal DNA testing.


Fig 1: Application scope of non-invasive prenatal DNA testing

2.Technical principle

In 1997, researchers from Chinese  University of Hongkong found that there existed cell-free fetal DNA in the plasma and serum of pregnant women’s peripheral blood. This makes it possible to detect chromosomal disorders of fetuses by checking pregnant women’s peripheral blood.

High-throughput sequencing technology enjoys fairly rapid growth in recent years, and features high throughput and low cost compared with traditional sequencing techniques. With the technology, dozens to hundreds of GB of data are generated in each experiment; and the cost of single nucleic acid sequencing falls drastically. 

Moreover, features such as high accuracy and sensitivity enable wide application of high-throughput sequencing technology to human health.


Fig 2: Cell-free fetal DNA contained in mother’s peripheral blood

Take the detection of Down's syndrome for example. According to studies, pregnant women with Down's syndrome fetuses show slightly higher content levels of No. 21 chromosome in their peripheral blood than normal pregnant women, because fetuses with Down's syndrome have one more No.21 chromosome than healthy fetuses.

The risk of a subject to bear a Down's syndrome baby can be evaluated after the relative content of No.21 chromosome in peripheral blood is tested, and content levels of No.21 chromosome in the peripheral blood of both the subject and ordinary pregnant women are analyzed. Combined with new generation high-throughput sequencing technology, non-invasive prenatal DNA testing ensures greatly higher sensitivity and accuracy as well as significantly shorter test period.


1.Test preparation   

Fasting is not required for blood drawing. Keep normal diet and daily schedule.

2.Test period

Professional test report is issued within 10 days after blood collection.

3. Channel of reservation

Hospital: obstetrician of cooperative hospital.

Tel: 4008-986-989 (customer service hotline)

Official website: http://www.annoroad.com/order_online

4. Insurance    

Annoroad buys insurance for all the pregnant women who are to take non-invasive prenatal DNA testing so that every one of them can be more assured.

About Down's syndrome

Down's syndrome is the most common chromosomal disorder of aneuploidy. With an incidence rate of 1/600-800, Down's syndrome is the primary cause of mental retardation for newborns. Since patients have one more No.21 chromosome than healthy people, the syndrome is also known as 21-trisomy syndrome.

Children with Down's syndrome have special facial features, short figure, mental retardation, no self-care ability, and multiple system complications. They suffer tremendously from physical illness and discrimination. Each family with a Down's syndrome child bears enormous psychological burden and economic pressure. 

In China, 26,600 babies are born with Down's syndrome annually, that is, one such newborn every 20 minutes. Currently, there are more than 600,000 cases of Down's syndrome nationwide. Over 100,000 yuan is needed for treating every newborn with Down's syndrome.

Down's syndrome is a fortuitous condition. The older the mother-to-be is, the higher the incidence of Down's syndrome for the baby. Every couple faces the risk of having a baby with Down's syndrome, which is impossible to prevent before pregnancy. Under the medical conditions nowadays, no effective treatment is available for Down's syndrome. It is wise and necessary to take a prenatal checkup during the course of pregnancy. This helps detect Down's syndrome, take efficient measures, and minimize the occurrence of Down's syndrome to newborns.

Fig 3: Relation between mother’s age and Down's syndrome incidence


Technical advantages

Non-invasive: The test requires only 5-10ml venous blood from the mother’s body and achieves non-invasive sampling.

Safe: Possibilities of abortion and intrauterine infection are avoided.

Precise: High-throughput sequencing technology delivers over 99% accuracy rate.

Simple: All-dimensional detection and services offer you all the convenience possible for a physical checkup.


Testing process

1. Appointment for test: Understand non-invasive prenatal DNA testing and decide whether to take the test;

2. Inspection sheet and informed consent: Fill out the Inspection Sheet and Informed Consent for non-invasive prenatal DNA testing under doctor’s guidance;

3. Blood sampling: Collect 5-10ml peripheral blood. Before your blood is taken, keep normal diet and rest; and there is no need to fast;

4. Report: A professional report is issued in 10 workdays after the subject’s blood is drawn.



For people

This technology applies to women with singleton pregnancy during week 12+0-26+6

In the following cases, you are advised to book the test service as soon as possible in order to understand the risk of aneuploidy in fetal chromosome:

1. Pregnant women whose serological screenings and imaging examinations indicate the critical point for risk of common chromosome aneuploidy (namely, 1/1000≤Down's syndrome risk value<1/270; 1/1000≤18-trisomy syndrome risk value<1/350);

2. Individuals with contraindications of interventional prenatal diagnosis (threatened abortion, fever, bleeding tendency, unhealed infection, etc.);

3. Pregnant women who have been pregnant for more than 20+6 weeks and missed the best timing for serological screening or conventional prenatal diagnosis; but have requirements for lowering risks of 21-trisomy syndrome, 18-trisomy syndrome or 13-trisomy syndrome).

The test should be used with caution for pregnant women in the following cases:

1. Advanced-aged pregnant women (≥35 years old) with high risks as suggested by prenatal screenings; pregnant women with other direct indications of prenatal diagnosis;

2. Women who are less than 12 weeks into pregnancy;

3. Pregnant women with heavy weight (weight>100kg);

4. Women who are impregnated by in vitro fertilization-embryo transplantation;

5. Women in twin pregnancy;

6. Pregnant women with malignant tumors.

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