Genetic diseases affect 3-5% of newborns. Learn which ones are common, how they are inherited, and which tests can provide clarity.
Key Facts About Hereditary Diseases
- Around 3–5% of all newborns are born with a congenital disease or malformation.
- Heart defects are among the most common congenital conditions.
- Risk factors include parental age, family history, and environmental influences.
- Preventive measures such as folic acid, iodine, vaccinations, and prenatal care can help reduce risks.
- Preimplantation genetic diagnosis (PGD) allows genetic screening of embryos before implantation.
- Genetic tests can provide valuable insights into potential hereditary risks.
Hereditary Diseases and Pregnancy: What You Need to Know
Are you pregnant or planning to start a family? You might be wondering:
- What are hereditary diseases?
- How likely is it that my child could inherit one?
- Can anything be done to reduce the risk?
You're not alone—many couples share these concerns when planning for a baby. In this article, you'll learn how common hereditary diseases are, how they are inherited, and what genetic testing options are available to provide clarity.
How Common Are Hereditary Diseases in Newborns?
Hereditary diseases are genetic conditions that can be passed from parents to children. Around 3–5% of all newborns are born with a congenital disease or malformation. These conditions may arise due to genetic mutations, chromosomal abnormalities, or environmental factors.
However, not every genetic mutation leads to disease. The likelihood of passing on a hereditary condition depends on the type of genetic disorder and inheritance pattern. Genes and chromosomes play a crucial role in determining whether a genetic change will be transmitted and whether it will cause symptoms.
Common Hereditary Diseases in Newborns
Some of the most well-known genetic conditions include:
1. Heart Defects
According to the WHO, heart defects are among the most common birth defects. They are often caused by a combination of genetic and environmental factors. Studies suggest that approximately 1% of all newborns in the USA and the UK are born with a heart defect.
2. Chromosomal Abnormalities
Changes in chromosome structure or number can lead to severe developmental disorders. Examples include:
- Trisomy 21 (Down Syndrome): In this condition, chromosome 21 is present in triplicate, leading to cognitive impairments and physical abnormalities. Approximately 1 in 700 babies is born with Down syndrome.
- Trisomy 13 (Patau Syndrome): A very rare but severe condition associated with malformations of the brain, heart, and other organs. It is estimated that 1 in 3,500 to 1 in 5,000 newborns is affected.
3. Neural Tube Defects (e.g., Spina Bifida)
This spinal malformation occurs due to incomplete closure of the neural tube in early pregnancy and affects approximately 2 in 1,000 births worldwide. Maintaining adequate folic acid levels can help reduce the risk.
4. Cystic Fibrosis (Mucoviscidosis)
An autosomal recessive metabolic disorder that affects the lungs and other organs. In Switzerland, around 1 in 3,300 newborns is affected.
5. Sickle Cell Anemia
A genetic blood disorder primarily affecting people of African, Mediterranean, or Middle Eastern descent. According to studies, the number of newborns with sickle cell disease in these regions increased by 13.7% between 2000 and 2021.
6. Thalassemia
A hereditary disorder affecting hemoglobin production, which can lead to severe anemia. Approximately 1.5% of the global population is affected.
7. Spinal Muscular Atrophy (SMA)
A neuromuscular disease that causes muscle weakness and movement limitations. Around 1 in 6,000 babies is born with SMA.
8. Hemophilia
Hemophilia is an X-linked recessive genetic disorder, meaning the affected gene is located on the X chromosome. This is why boys have a higher risk of developing hemophilia, as they have only one X chromosome. Girls can be carriers of the affected gene without developing the disease themselves. Approximately 1 in 5,000 male newborns is affected.
Genetic Testing for Hereditary Diseases
Both modern prenatal diagnostics and preimplantation genetic testing (PGT) offer various methods to screen for genetic disorders.
Genetic Tests Before Pregnancy
- Carrier Screening: A genetic test performed before or during pregnancy to determine whether parents are carriers of specific hereditary diseases, such as cystic fibrosis.
- Preimplantation Genetic Testing (PGT): During assisted reproduction techniques like in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI), embryos can be screened for specific genetic disorders before implantation. This method is particularly recommended for couples with known hereditary conditions or recurrent miscarriages.
Non-Invasive Prenatal Testing
- Ultrasound: Ultrasound scans can help detect structural abnormalities, such as heart defects or brain malformations, as well as early signs of growth disorders.
- First Trimester Screening: Typically performed between weeks 11 and 14 of pregnancy, this test measures the nuchal translucency (NT) of the fetus. Increased NT may indicate chromosomal abnormalities or heart defects. Additionally, maternal blood tests measure PAPP-A and free β-hCG to refine risk assessment.
- Non-Invasive Prenatal Testing (NIPT): A simple blood test from the mother, available from week 10 of pregnancy, can screen for chromosomal conditions such as trisomy 21, 18, and 13. Popular NIPT options include the Harmony Test and Panorama Test.
Invasive Prenatal Tests
- Amniocentesis (Amniotic Fluid Test): A small sample of amniotic fluid is extracted and analyzed for genetic abnormalities.
- Chorionic Villus Sampling (CVS): A tissue sample from the placenta is taken to enable early genetic testing.
- Cordocentesis (Fetal Blood Sampling): A blood sample is drawn from the umbilical cord. This procedure is less common than amniocentesis or CVS and is primarily used when rapid results are needed or if a fetal blood disorder is suspected.
The decision to undergo or forgo prenatal testing is a very personal one. It raises questions about how to handle the potential diagnosis of a severe disability. It is important to understand that a genetic result does not always provide a clear indication of the severity of the disability or the child's future quality of life. Many people with genetic disorders lead fulfilling and normal lives, while others face significant challenges.
Risk Factors for Hereditary Diseases
There are various factors that can increase the risk of a genetic disorder:
- Parental Age: Particularly women over 35 and men over 40 have a higher risk of genetic mutations. Additionally, the quality of eggs declines with age, which increases the risk of miscarriage and chromosomal abnormalities.
- Family History: If hereditary diseases are known to run in the family, the risk of inheritance is higher. The type of inheritance (dominant, recessive, X-linked) determines the likelihood of passing on the condition.
- Personal Genetic Disorder: If someone has a genetic disorder themselves, they may pass it on to their children. For example, if one parent has Huntington's disease, each child has a 50% risk of inheriting the condition.
- Ethnic Background: Certain genetic disorders are more common in specific populations. Examples include sickle cell anemia among people of African descent or thalassemia among those of Mediterranean origin.
- Environmental Factors: While not directly genetic, certain environmental factors during pregnancy can increase the risk of congenital abnormalities. These include exposure to certain chemicals or radiation, uncontrolled diabetes, or other chronic maternal conditions.
Pregnancy Care and Prevention
Comprehensive pregnancy care can help detect risks early on. Expectant parents with a family history of genetic disorders can seek genetic counseling. Additionally, a healthy lifestyle, including adequate folic acid intake, plays a crucial role in preventing certain birth defects. Therefore, it is important for pregnant women to attend regular prenatal check-ups.
How Can Hereditary Diseases Be Prevented?
Although many hereditary diseases are genetically determined and not fully avoidable, the risk of certain congenital conditions can be significantly minimized through preventive measures. These include:
- Adequate folic acid intake
- Sufficient iodine intake
- Vaccinations (particularly rubella)
- Comprehensive pregnancy care
These measures can help reduce the risk but do not provide an absolute guarantee against all congenital diseases.
Frequently Asked Questions about Genetic Diseases
What should I do if I get an abnormal test result?
An abnormal test result can be a significant emotional burden for pregnant women and prospective parents. In such cases, psychosocial counseling is essential to receive emotional support and make informed decisions. In Switzerland, after a positive result, parents have the opportunity to seek detailed counseling on options such as medical treatments or a potential abortion.
How are genetic diseases inherited?
Certain fetal conditions are caused by changes (mutations) in the genetic material. Inheritance can occur in different ways:
- Dominant-recessive: A mutation in a single gene can be dominant or recessive. Dominant mutations manifest with just one copy of the altered gene, while recessive mutations only show effects when both parents pass on the defective gene. A well-known example of an autosomal-recessive genetic disorder is cystic fibrosis. Both parents must be carriers of the defective gene for the child to inherit the condition.
- Chromosomal anomalies: Errors in the number or structure of chromosomes, such as trisomies, can lead to developmental disorders. The sex chromosomes can also be affected, such as in Fragile X syndrome.
- Multifactorial inheritance: Some diseases arise from the interplay between genetic and environmental factors. Spina bifida (open spine) is an example of a condition influenced by a combination of genetic and environmental factors.
- New mutations: In rare cases, a spontaneous mutation in a germ cell (egg or sperm cell) can occur, which is then passed on to the child without the parents being affected. An example of this can be certain cases of muscular dystrophy.
Genetic Diagnostics: Decision Support for Prospective Parents
We all carry genetic variations, but only a small portion of them actually lead to diseases. Thanks to modern genetic testing, such as preimplantation genetic diagnosis (PGD), certain genetic diseases can be minimised before a pregnancy.
In addition, prenatal diagnostics allow early detection of diseases during pregnancy. Combined with genetic counseling and psychosocial support, couples can make well-informed decisions about their family planning.
At our fertility clinic in Zurich, we provide comprehensive care for couples trying to conceive and offer a wide range of services that go far beyond the purely medical aspects.
