prenatal diagnosis
Release time : 01/18/2025 18:13:27
With the development of science and technology, especially molecular biology and medical genetics, prenatal diagnosis is also developing.
Prenatal diagnosis can accurately and quickly detect an increasing number of birth defects, and now it can be safe and accurate to diagnose at the early stage of embryonic development.
With the widespread adoption of prenatal diagnosis, the incidence of diseases in newborns has decreased significantly compared to before.
What is Prenatal Diagnosis? Prenatal diagnosis (prenatal diagnosis) refers to a series of examinations and diagnoses conducted before the birth of an embryo or fetus, aimed at evaluating its developmental status, whether pregnant women and fetuses are suffering from disease, or whether pregnancy is normal.
This allows for the determination of whether an embryo, fetus, or pregnant woman is currently normal and can detect diseases in advance, allowing for intrauterine treatment at the appropriate time. For conditions that cannot be treated, it also enables early detection, allowing for a decision on whether to continue pregnancy.
Prenatal diagnosis includes prenatal screening and diagnostic testing. If there is a high likelihood that the fetus will inherit a genetic disorder, prenatal screening should be performed. Diagnostic testing must be based on a confirmed case of the disorder, which usually requires genetic counseling first.
Prenatal diagnosis methods mainly include invasive and non-invasive methods.
Among them, invasive methods are the main methods, of which amniocentesis is the most commonly used one.
Prenatal screening started relatively late in my country. It was only in 1998 that foreign databases and risk value calculation software were gradually introduced. It was not until 2002 that my country officially designated the "Measures for the Management of Prenatal Diagnosis Technology."
Subsequently, across the country, prenatal diagnostic institutions began to be approved and gradually standardized the screening for trisomy 21, trisomy 18, neural tube defects, and other prenatal diagnoses during the second trimester.
Prenatal diagnosis can be classified into invasive prenatal diagnosis and non-invasive prenatal diagnosis.
Amniocentesis and CVS are the main invasive prenatal diagnostic procedures. Ultrasound imaging is the non-invasive prenatal diagnostic procedure.
However, it is important to note that invasive prenatal diagnosis can cause varying degrees of harm to both the mother and the fetus. It should generally be used with caution, but these damages can be minimized through improvements in operational techniques and experience accumulation with the use of advanced instruments such as ultrasound.
Amniocentesis, a pivotal technique for prenatal diagnosis of chromosomal abnormalities, is typically performed between the 16th and 22nd week of gestation. During this procedure, an ultrasound scan is used to extract 10-20ml of amniotic fluid from the uterus. The amniotic fluid contains cells shed by the fetus, which can be utilized for various tests.
1. Down syndrome (21 trisomy), also known as anencephaly, is the most common chromosomal disorder, primarily caused by chromosome number and structural abnormalities.
Normally, the number of chromosome 21 is 2, but this disease has 3, and there is one extra chromosome.
Since the risk of developing this disease increases significantly after the age of 30, it is generally recommended that pregnant women over the age of 30, especially those over 35, have this prenatal diagnosis.
Individuals with Down syndrome typically exhibit severe intellectual impairment compared to normal individuals, short stature, hypotonia, and specific facial characteristics such as wide-set eyes, an upturned outer corner of the eye, a low nasal bridge, often protruding mouth and tongue, and drooling. Additionally, they may also suffer from congenital heart diseases and congenital megacolon.
2. Edward's syndrome, also known as Trisomy 18 syndrome, primarily arises from the failure of meiosis in parental germ cells during gamete formation. Its primary manifestations include delayed growth and development before birth, low birth weight, poor sucking ability, feeding difficulties, intellectual disabilities, a small but elongated head, broad palpebral fissures, short neck, loose skin, and hypotonia in infancy followed by hypertonia later in life. Moreover, approximately 90% of individuals with this condition also suffer from congenital heart defects and external genital abnormalities.
Even if the treatment is successful, only 95% of fetuses survive to birth. After birth, only a majority of them can be kept alive, 50% die within two months.
3. Turner syndrome, also known as congenital gonadal dysgenesis or female gonad hypoplasia, occurs in female infants. It is characterized by the absence of one X chromosome, resulting in clinical symptoms such as primary amenorrhea, webbed neck, elbow hyperextension, and short stature.
4. Detection of intrauterine infection (such as Cytomegavirus, CMV) can be confirmed through the detection of viruses in amniotic fluid by culture or PCR to determine whether there is fetal infection.
5. Decompression during polyhydramnios.
Chorius sampling (CVS) means that in the first trimester, a small number of fetal villi containing fetal cells in the ectotrophoblast are extracted through the vagina or abdomen under ultrasound guidance to screen for chromosomal abnormalities.
Down's syndrome (trisomy 21), Edward's syndrome (trisomy 18), Turner's syndrome, etc. can be found.
The advantage is that the diagnosis can be discovered as quickly as possible. On the one hand, it can greatly relieve the pressure on pregnant women. On the other hand, it can also terminate pregnancy as early as possible and reduce harm to pregnant women.
However, it should be noted that this operation has a combined risk of miscarriage of as high as 2-3%, and is generally scheduled for 11 weeks.
Maternal cell contamination may also occur, and neural tube defects and other structural abnormalities cannot yet be diagnosed.
Percutaneous umbilical vessel puncture (Cordocentesis), a method that is rarely used, can not only diagnose chromosomal abnormalities, but also treat Rh alloimmune hemolysis.
Pre-implantation genetic diagnosis, fetoscopy, non-invasive prenatal diagnosis ultrasound: through ultrasound, it can assess the gestational age, determine the fetal sex, placenta, whether there are multiple pregnancies, whether the fetus is abnormal, etc.
Why is it necessary to undergo prenatal diagnosis? By conducting regular prenatal examinations, parents can be informed in advance about whether the fetus is normal. This allows for early planning and preparation for the baby's health needs. For example, knowing that a certain condition will not affect the child if they are born can help parents mentally, socially, financially, and medically prepare accordingly.
Additionally, parents have the right to be informed. Prenatal diagnosis allows them to exercise the right to terminate a pregnancy before the baby is born.
If it is discovered that fetal diseases can be treated, then appropriate timing for medication or surgical treatment can be seized before birth or after birth.
The medical information presented in this document is for reference only and should not be used for medical diagnosis or treatment.
If you experience discomfort, it is recommended to seek medical attention immediately. The diagnosis and treatment of illnesses should be based on face-to-face consultations.