Detection of Down syndrome when the fetus is only 11 to nearly 14 weeks old

Down syndrome - a form of mental retardation that causes patients to become ignorant and almost incapable of learning - is the most common genetic disorder among living babies and is also the disorder The most omitted disorder on ultrasound. This syndrome is incurable, causing a huge burden for families and society. With the development of medicine today, we can detect up to 90% of cases of Down syndrome since the child was only 11 to 13 weeks 6 days in the womb.

What is down disease?

Down syndrome is a chromosome condition caused by the presence of all or part of the chromosome 21 extra. . This syndrome is most common among diseases caused by chromosomal disorders. For every 800-1,000 babies, there is 1 child with Down syndrome.

The risk of children with Down syndrome increases with the age of the mother. Therefore, since the early 70s of the last century, some developed countries have applied measures to screen Down syndrome based on the age factor of mother. All women over 35 years of age are consulted for amniocentesis (sucking amniotic fluid through the abdominal wall to check the fetal chromosome, thereby diagnosing Down syndrome). However, the proportion of Down syndrome detected is only nearly 30%. This means that out of 10 Down children, only 3 were found to be antenatal to terminate their pregnancy and the remaining 7 children were missed.

By the 1980s , the screening of Down syndrome was based on the combination of maternal age and testing of maternal fetal biomarkers (AFP, HCG and UE3) at 16-18 weeks' gestation to check for association risk. Down syndrome in a child before a woman is consulted whether or not to have amniocentesis. Please also add that amniocentesis may increase some risks to the fetus, such as premature birth or miscarriage. This method helps detect about 60% of Down syndrome. This means that if the biochemical test for screening Down syndrome for all pregnant women in the period of 16-18 weeks, only 6 out of 10 Down babies are detected before birth.

The skin is normal.

By the 1990s, experts noted a link between the dense skin faintness in the fetus and Down syndrome. The thicker the skin, the greater the risk of Down syndrome. Remember, this sign only appears for a period of 11 weeks to 13 weeks 6 days. After 14 weeks, the skin of the neck will return to normal and this does not mean normal pregnancy. Screening for Down syndrome based on mother's age in combination with skin dullness for 11 weeks to 13 weeks 6 days will help detect nearly 80% of DOWN syndrome. It should be noted, if the skin is thick but the chromosome is normal (children do not have Down syndrome), then the child is still at high risk of fetal heart defects. If skin dullness is> 3.5mm, about 1/3 of cases will have chromosomal abnormalities. In the remaining 2/3 cases, there will be 1/16 cases of heart defects (Statistics of the Institute of Fetal Medicine, located in London - England). Therefore, when the fetus has thick skin and normal chromosomes, it is still necessary to have an ultrasound cardiac specialist at 22 weeks.

Currently, the screening of Down syndrome is based on the combination of maternal age factor, ultrasound measurement of the dullness of the skin and testing of fetal biomarkers (PAPP-A, free beta HCG) in maternal blood at the age of 11 weeks pregnant -13 weeks 6 days. All of these factors will be calculated by a specialized software combined, providing a final risk of the ability of a child to give birth to a child. If the risk is high, women will be consulted for amniocentesis. This method helps detect 90% of Down syndrome. Thus, of 10 Down children, only one child was missed.

Mothers 40 years old, 12 weeks pregnant, skin is 4.5mm thick.Risk of Down syndrome: 1/2.It means that in 2 mothers at the age of 40 and pregnant at 12 weeks, the skin is 4.5mm thick, one woman will give birth to Down syndrome.In this case, the mother needs amniocentesis for a definite diagnosis.(Photo: TN).

Recently, Tu Du Hospital (Ho Chi Minh City) cooperated with the Australian Ultrasound Association (ASUM) and the Fetal Medicine Organization (FMF) in London to open a training course on ultrasound to measure the dullness of skin and birth techniques. Set up each other (take a sample of the fetus to check for chromosome sets) to screen and diagnose early Down syndrome: from 11-13 weeks 6 days. About 140 practitioners from 32 southern provinces came to attend. Tu Du Hospital is the first place in the whole country to be officially recognized to be capable of measuring the dullness of skin and to use specialized software to calculate the risk of DOWN syndrome from FMF London based on the combination of age factor , thickness of the nape of the skin and biochemical tests of maternal blood at gestational ages 11 to 13 weeks 6 days.

Thus, for the best screening of DOWN syndrome, pregnant women need an ultrasound to measure the dullness of the skin and biochemical screening for 11 weeks -13 weeks of 6 days. FMF software will help calculate the risk of DOWN syndrome. If there is a high risk (> 1/300), pregnant women will be consulted with each other's biopsy or amniocentesis for a definitive diagnosis.

Dr. Ha To Nguyen (Head of Imaging Department of Tu Du Hospital)