Down syndrome: causes, signs,diagnostics

Update: October 2018

Down syndrome was first described by a famous British doctor.
By John Langdon Down, who began his research
work in 1882, and in 1886 published it publicly

This is one of those pathologies that everyone has an idea about.
person. This disease especially worries future moms who with
apprehensively awaiting the first screening. According to recent decades,
This pathology occurs in every 700 born baby.

The statistics of the last few years shows another figure – 1
born child with pathology for 1100 newborns, what has become
possible thanks to high-precision prenatal diagnosis and early
termination of such a pregnancy. About 80% of children with this pathology
born in women younger than 35 years old – despite being relatively small
the risk of the development of this chromosomal pathology in a fetus, in this
age group has a peak birth rate. Every year in everything
about 5,000 newborns with the syndrome are added to the world

Down syndrome also affects girls and boys alike.
the disease has no ethnic distribution and is found

In 2006, on March 21, the International Day of People with
синдромом Down’s This day is spent to raise
public awareness in matters of this frequent pathology and
improve the quality of life of sick people. The number 21 was chosen
due to the cause of the disease – trisomy 21 chromosome, and a month
March personifies trisomy because it is the third month in

Causes of Down Syndrome

Causes of Down Syndrome lie in the intrauterine
the formation of chromosomal pathology of the fetus, characterized by
the formation of additional copies of genetically pledged material
Chromosome 21, or the entire chromosome (trisomy), or sections
chromosomes (for example, due to translocation). Normal karyotype
A healthy person consists of 46 chromosomes, and in Down syndrome
the karyotype is formed by 47 chromosomes.

The causes of Down Syndrome are in some way not related to
environmental conditions, parental behavior, admission
any drugs and other negative phenomena. it
random chromosomal events that unfortunately are impossible
prevent or change further.

Risk factors for down syndrome

The age of the future mother affects the risk of developing Down syndrome in

  • in the age range from 20 to 24 years probability
    the formation of this pathology is 1 to 1562;
  • at the age of 25-35, this risk is already 1 in 1000;
  • at the age of 35-39, the risk increases to 1 in 214;
  • over the age of 45, the risk increases to 1 in 19.

As for the age of the future of the pope, the risk is scientifically proven
Births of children with this syndrome in men over 42 years old.

There is a computer program “PRISCA”, which takes into account
data from ultrasound, physical gynecological studies and other
factors and calculates the risk of congenital abnormalities of the fetus. For
calculation of the risk of Down syndrome, Edwards syndrome, the risk of developing
defects of the central nervous system (neural tube defect)
taken into account:

  • Mother’s age
  • Smoking
  • Gestational age
  • Ethnicity
  • Body weight
  • Number of fruits
  • Diabetes disease
  • IVF availability

Is it possible to pass Down syndrome by inheritance?

Trisomy 21 chromosome (approximately 90% of cases)
diseases) is not inherited and not inherited; also
most relevant to the mosaic form of pathology. Translocation form
diseases can be hereditary if
any of the parents had a balanced chromosomal
restructuring (this means that part of the chromosome changes places with
part of some other chromosome without causing pathological
processes). When such a chromosome is transmitted to a subsequent generation
there is an excess of genes 21 chromosomes, leading to the disease.

It is worth noting that children born to mothers who suffer
Down syndrome, in 30-50% of cases are born with the same

How to learn about Down Syndrome during pregnancy?

Since the causes of Down syndrome in a fetus are genetically
This pathology of the child can be recognized as early as
the womb. If down syndrome is suspected, signs of
pregnancy is determined in the first trimester.

Diagnosis of Down syndrome in the first trimester is
combined screening analysis that determines the risk of developing this
pathology in the fetus. The study is conducted strictly in the period from 11 to
13 weeks and 6 days of pregnancy.

  • Determination of the level of β-subunit of chorionic gonadotropin
    (pregnancy hormone hCG) in the venous blood of the mother. With this
    chromosomal abnormality of the fetus will be determined by elevated levels
    CG β-subunits of more than 2 MoM;
  • Determining the level of PAPP-A – protein-A plasma of pregnant women,
    associated with pregnancy. High risk of syndrome is associated with
    PAPP-A indicator less than 0.5 MoM;
  • Determination of the thickness of the collar space using ultrasound
    fetus. In Down Syndrome, this indicator exceeds 3 mm.

When combined with the three indicators described, the probability of the syndrome
Dina in the fetus is 86%, i.e. diagnostics является достаточно
accurate and indicative. For принятия решения о сохранении
pregnancy or its termination to the woman in whom
signs of Down syndrome in the fetus, it is proposed to produce
transcervical amnioscopy.

In this study, a fence is made through the cervix.
chorionic villi that are sent for genetic research,
according to the results of which it is already possible with absolute certainty
confirm or refute this diagnosis. Study not
belongs to the group of mandatory, the decision to hold it take
parents. Because it carries a certain risk for
further course of pregnancy, many refuse to

Diagnosing Down Syndrome in the Second Trimester – This is also
combined screening that is conducted between 16 and 18
for weeks.

  • Determining the level of hCG in the blood of a pregnant woman – with Down syndrome
    figure above 2 MoM;
  • Determining the level of a-fetoprotein in the blood of a pregnant woman (AFP) –
    in Down syndrome, the index is less than 0.5 MoM;
  • The definition of free estriol in the blood – an indicator of less than 0.5
    MoM is characteristic of Down syndrome;
  • Determination of inhibin A in a woman’s blood – more than 2 MoM
    characteristic of down syndrome;
  • УЗИ fetus. If Down syndrome is present, signs of an ultrasound scan will

    • smaller fetus relative to the norm for a period of 16-18
    • shortening or absence of the nasal bone in the fetus;
    • size reduction of the upper jaw;
    • shortening of the humeral and femoral bones of the fetus;
    • increase in bladder size;
    • one artery in the umbilical cord instead of two;
    • lack of water or lack of amniotic fluid;
    • учащенное сердцебиение у fetus.

With a combination of all signs, the woman is offered an invasive
diagnostics для проведения генетического исследования:

  • transabdominal aspiration of the placenta villus;
  • transabdominal cordocentesis with vascular puncture
    umbilical cord

The selected material is investigated in the genetic laboratory and
allows you to accurately determine the presence or absence of this pathology
у fetus.

In 2012, British scientists developed a new
high-precision test for the presence of Down syndrome in the fetus, the result
which is estimated at 99%. It consists of a blood test.
pregnant and suitable for absolutely all women. However, until he
introduced into world practice.

How is the issue of termination of pregnancy in determining
high risk of down syndrome in fetus?

When children are born with Down Syndrome, the causes of the incident
A genetic glitch is really impossible to establish. Many
parents see it as a test and consider themselves
endowed with a special function of education and development of such a child.
But before every pregnant woman with a high risk of this pathology arises
the question of deciding the fate of their pregnancy. The doctor does not have the right
insist on interruption but he is obliged to clarify this issue and
warn of all likely consequences. Even when detected
pathologies incompatible with life, no one has the right to incline
woman to the decision to have an abortion (see the consequences), and even more so
make it do it.

Thus, the fate of pregnancy with fetal pathology is decided
only parents. Parents have the right to repeat the diagnosis in another
laboratories and clinics, consult with several geneticists
and other professionals.

Symptoms of Down Syndrome in a Newborn

Symptoms of Down syndrome in newborns are determined immediately after
of birth:

  • shortened skull;
  • small head size;
  • irregular ear shape;
  • flattened facial skull;
  • saddle nose;
  • flat nose bridge;
  • small mouth;
  • small chin;
  • thick, furrowed tongue;
  • oblique eye section;
  • open mouth;
  • skin folds located on the inner corners of the eyes;
  • short neck;
  • fold of skin on the neck;
  • short upper and lower limbs;
  • short fingers;
  • flattened wide palms;
  • horizontal fold on the palms;
  • the concave shape of the little fingers;
  • visible distance between the first and second toes;
  • weak muscle tone.

When children with Down syndrome are born, external signs
listed above, almost everything will be determined. Diagnosis
confirmed after passing the genetic analysis on the karyotype.

Can a child with Down syndrome grow mentally and
physically complete person?

itт вопрос обязательно встает и перед теми родителями, которые
still deciding whether to terminate or maintain a pregnancy, and before
those who already carry a precious little bag with a newborn

The consequences of the formation of an additional copy of the chromosome
vary greatly and depend on the amount of excess genetic
material, from the genetic environment, and sometimes from the pure
randomness. Of great importance is the individual program.
development of such a child and, of course, comorbidities,
which such children there is a lot.

Of course, these are not deep disabled people, but children capable of
to learn, develop and become adapted individuals in
modern social environment. At the same time, it is important to understand that
every child with Down syndrome will have different degrees
severity lag in mental, verbal, physical development.
Putting them on one line with healthy children is incorrect, and not
it is necessary, but it is also impossible to consider “abnormal people”.

The particular phenotype makes this pathology recognizable. Really,
hide from prying eyes such a feature of your child is not
work out. But it is better to take your baby from the first breath
what he is, be proud of him and not hide from people. Yes, these children
special, but far from hopeless. Moms of children suffering much
more serious pathologies would give everything for the opportunity
to switch places with moms down, so that the child could live and
to smile.

Автор: врач-гигиенист, эпидемиолог

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