The Meaning of Prenatal Diagnosis Seen from the Attempted Murder Incident of a 1-Year-Old with a Severe Disease
What are genetic disorders? What if prenatal diagnosis were conducted during pregnancy? What should you do if you cannot undergo it? I would like to explain these topics in detail below.
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What does 'hereditary disease' mean? What are the conditions for undergoing prenatal diagnosis, and what kind of care is available if it cannot be done?
The news of a 40-year-old mother being arrested for killing her third son, a one-year-old with a hereditary rare disease, has attracted attention. The eldest son is a carrier of the same condition but has not developed symptoms, and the second son died from the same disease. The mother wished to undergo prenatal diagnosis for the third son, but it was not possible, and she faced childbirth without being mentally prepared.
We would like to provide detailed explanations below on topics such as: What is a hereditary disease? What if prenatal diagnosis had been performed during pregnancy? What should be done if it cannot be performed?
What is a Gene?
First, let's understand what genes are.
The human body is composed of approximately 60 trillion cells. Each of these cells contains a nucleus, and within that nucleus are 46 chromosomes. Half of these chromosomes are inherited from the father and the other half from the mother.
These chromosomes are packed with a double helix structure resembling a twisted ladder, called "DNA" (deoxyribonucleic acid). DNA is the substance that carries genetic information, made up of four nucleotide bases: adenine (A), guanine (G), cytosine (C), and thymine (T). These bases are arranged in various sequences. This sequence determines the "genetic information" that creates individual traits in humans.
Through inheritance, characteristics such as constitution, facial features, and personality traits are passed from parents to children. However, not only physical traits but also diseases can be inherited due to mutations in genes or chromosomes.
About Genetic Disorders
Genetic disorders refer to diseases caused by mutations in chromosomes or genes, and they are classified into three types: chromosomal abnormalities, single gene disorders, and multifactorial inheritance.
Chromosomal Abnormalities
An excess or deficiency of genes within entire or partial chromosomes is the cause. For example, Down syndrome results from trisomy 21, where typically chromosomes exist in pairs (disomy), but the 21st chromosome has three copies (trisomy).
Monogenic Disorders
A mutation in a single gene (single gene disorder) is considered the cause, and mutations can occur either spontaneously in the child's generation (de novo mutations) or be inherited from the parent's generation. There are thousands of types of disorders, and due to genetic abnormalities, fundamental treatment is often challenging. Some disorders also manifest in adulthood after development.
Polygenic Disorders
They are involved in the causes of most diseases such as diabetes and Alzheimer's disease. Since they develop from influences of both environment and genetics, in many cases, onset can be suppressed through prevention.
What Can Genetic Analysis Reveal?
Genes can be inherited not only from parents but also from grandparents, and they can arise from spontaneous mutations. While genetics are not the sole determinant and some causes remain unknown, if a previous pregnancy resulted in a baby with chromosomal abnormalities, the likelihood of having another baby with the same abnormality in a subsequent pregnancy is considered to be several times to tens of times higher than the probability for a woman of the same age to have a baby with similar symptoms.
Genetic analysis during pregnancy refers to prenatal testing conducted in the first half of pregnancy as part of prenatal diagnosis (such as NIPT or amniocentesis).
Genetic analysis involves testing related to congenital anomalies, numerical abnormalities of chromosomes, and diseases based on gene mutations. It is performed to accurately diagnose the potential abnormalities in the fetus during pregnancy.
Therefore, certain conditions are required for testing, such as one of the parents being a carrier of chromosomal abnormalities, or being unaffected carriers, or having a history of abnormal pregnancies or births.
Furthermore, the diagnostic process requires multiple steps, including gathering detailed personal medical histories, family histories, and examination data from various organs. It necessitates specialized medical staff trained in diagnostic procedures and ongoing monitoring. Let's explore what is necessary to undergo such testing.
About Prenatal Diagnosis
renatal diagnosis refers to a series of tests conducted during pregnancy. Its purpose is to diagnose the fetus, confirm the presence of pregnancy, fetal viability, position, and orientation, as well as to check for conditions such as placenta previa that may pose risks to the mother.
Additionally, it can detect some congenital conditions (such as structural abnormalities or chromosomal abnormalities) as the fetus develops. Particularly, Non-Invasive Prenatal Testing (NIPT) has gained attention in recent years due to its ability to be performed early and with minimal risk of stillbirth or miscarriage through a small blood sample.
To undergo testing at accredited facilities, conditions such as:
- Maternal age of 35 years or older at delivery
- Pregnant women identified with possible chromosomal disorders through serum marker tests or fetal ultrasound examinations
- Pregnant women who have previously experienced pregnancies or births with chromosomal disorders
- Either parent having a chromosomal abnormality
Meeting one of these conditions is required.
In addition to preparing emotionally if fetal abnormalities are detected, the purpose of prenatal diagnosis traditionally involved deciding between continuing the pregnancy or terminating it, followed by medical care after birth. However, in recent years, there has been a growing consideration for "fetal therapy" as an option.
What is Fetal Therapy?
Medical facilities offering prenatal diagnosis are still limited in number in Japan. If abnormalities are detected through prenatal diagnosis, fetal therapy is a treatment conducted on the fetus inside the uterus through the mother's body, aiming to prevent conditions where the fetus may die in utero or shortly after birth due to illness. It was developed alongside the advancement of fetal diagnosis in the 1960s. Treatments are broadly categorized into medical treatments administered via the mother's body, such as transfusions, fluids, and medications, and surgical treatments directly performed on the fetus through procedures like uterine or maternal skin incisions. At present, not all conditions can be treated this way, but congenital heart disease, hydrocephalus, twin-to-twin transfusion syndrome, among others, are targets for treatment.
If surgery is successful, it allows for the continuation of the pregnancy and improves the prognosis for the fetus.
What to Do If Prenatal Diagnosis is Not Available
However, while the number of facilities offering tests for conditions like chromosomal abnormalities has been increasing in recent years, these tests are not available at every medical institution. This can result in situations where individuals cannot undergo testing due to lack of nearby facilities or inability to secure appointments. Moreover, individuals who are carriers of chromosomal abnormalities without symptoms or those whose conditions are not within the scope of testing for chromosomal or genetic abnormalities may also find themselves unable to undergo testing.
If unable to undergo testing, one option is genetic counseling. This is recommended for:
- Individuals with advanced maternal age at risk of chromosomal disorders
- Those who have previously given birth to a child with chromosomal or genetic disorders
- Individuals concerned about passing on genetic disorders to their children due to personal, spousal, or familial history
- People identified as having a high probability of chromosomal disorders through screening
- Anyone considering genetic prenatal diagnosis for any other reason
Furthermore, many individuals may feel uncertain about where to seek advice or how to access support, which can lead to frustration. Issues may also arise during genetic counseling, where some individuals may feel they did not receive the information they needed or expected.
Currently, with the accessibility of social media networks (SNS) and personal parenting blogs, it has become easier to access information locally. This can provide opportunities for those facing illnesses when they cannot physically visit facilities or undergo tests due to various reasons.
Conclusion
Genetic disorders were once considered incurable, but in recent years, advancements in medicine have revealed the causes of many diseases. As a result, the overall mortality rate among pediatric patients with chronic illnesses has decreased, saving the lives of many patients.
Support available after birth has gradually increased, aiming to create a more livable society even for those with disabilities. However, there are still many aspects that have not fully permeated society.
It is crucial for systems that are easy to understand and accessible to be widely implemented as soon as possible. Equally important is gaining correct knowledge and information to face these challenges.