Posted by Chantel Martiromo, Article By Kyle J. Norton
Birth defects is defined as a
condition in which the baby was born with structural or functional
abnormalities that can lead to physical or mental disability.
Genetic disease is a
inherited disease, passing down from generation to generation, caused
by abnormal mutation of a gene or a group of genes or or chromosomal
defects, of which can lead to birth defects.
Types of genetic diseases
Genetic diseases can be classified as the below
A. Chromosomal abnormalities
The diseases can be caused by genetic passing through from the
parent or an error in cell division. Chromosomal abnormalities can be
divided into two basic groups, numerical and structural anomalies.
A.1. Numerical anomalies
Numerical anomalies is a condition of missing either a chromosome
from a pair or has more than two chromosomes of a pair. In other words,
it has more or fewer chromosomes than the normal number. Types of
numerical anomalies include
a. Down syndrome (trisomy 21)
It is a genetic disease caused by the the presence of all or part
of an extra 21st chromosome genetic material and most common cause of
birth defects in the US, according to the statistic 1 in 800 born with
Down syndrome each year. As of today, there are no treatment for
children with diseases.
b. Turner syndrome -
Turner syndrome is a type of chromosome abnormalities with the
absence of part or all sex chromosomes, leaving a single X chromosome,
or 45 total in new born girl. According to the statistic, 1 in 2500
babies in US are born with Tuner syndrome.
A.2. Structural anomalies
It is a result of structural problem of the chromosomes themselves and can be classified as below 1. Deletion mutation
It is a result of missing part of a chromosome or DNA code. many
researchers believe that it may be the result of errors in the process
of chromosome cross over during the early stage of egg fertilization.
a. Cri du chat
It is due to the deletion of part of the short arm of chromosome 5.
Currently, there is no treatment for the disease.
b. Muscular dystrophy
It is a result of weaken muscles that affect the movement of the
new born as a result of the defects of muscles protein that cause the
death of the cell and tissue of the muscles. Currently, there is no
cure for the disease and most infant born with muscular dystrophy are
died at a young age.
It is a genetic disorder caused by inversion of the part of broken
DNA reattachment. If the inversion of the part of DNA is small, it may
not cause any problem to the newborns as in most cases, happened to
part of the chromosome 9,
It is a rearrangement of parts between nonhomologous chromosomes.
a. Balanced translocation - the DNA is equally exchanged between
chromosomes and none is lost or added. A parent with a balanced
translocation is healthy, but he/she may be at risk for passing
unbalanced chromosomes in a pregnancy.
b. Robertsonian translocation
It is a case of a centric fusion, as a result of chromosomal
rearrangement occurs in the five 13, 14, 15, 21, and 22. chromosome
pairs, causing only 45 chromosomes in each of their cells.
It is a result of a parts of a chromosome has broken off and formed
a ring. Many researchers believe that ring chromosome abnormality may
be caused by genetic damage of a mutagens. The disease may only cause
symptoms if it happens to a region of repetitive DNA sequences at the
end of a chromosome,
B. Single gene defects
It is a result of single gene defect out of 40-60,000 genes
presented in the human body leading to the leads to alternation of the
DNA code as a result of an defect amino acid sequence in the proteins.
Types of Single gene defects include
As a result of only one abnormal gene from either parent.
Researchers found that the risk of the disease increased by a 50% for a
baby born with parent with the disorder, including Huntington's
disease, Marfan syndrome, etc.
As a result of both parents are diagnosed with the disease. Bay
born with above parent has a 25% inherited the mutation gene,
including cystic fibrosis, sickle cell disease, Tay Sachs disease,
C. X-Chromosome abnormality
Women who carry the mutated genes of the X chromosome have 50% risk
in giving birth to a X-link related birth defects. Types of disorder
is depended to the degrees of expression of the mutation. In X
chromosome abnormality, men are affected and women are carriers.
a. Duchenne muscular dystrophy
It is a mutations in the dystrophin gene of the X chromosome that cause rapid muscle desperation.
a bleeding disorder caused by low levels, or absence of, a blood
protein. Patients with haemophilia may suffer severe and frequent
bleeds, depending to the severity of the disease.
D. Multifactorial problems
It is a type of genes mutation involved many factors, including the
environment in the causation of birth defection, including cleft lip
or cleft palate, neural tube defects, etc.
E. Teratogenic problems
It is type of mutation gene abnormality caused by exposure to
certain chemicals, radiation, alcohol, heavy chemicals, certain
1. Blood test
a. Maternal Blood Screen
It is a blood test for the levels of proteins, human chorionic
gonadotropin (hCG) and pregnancy associated plasma protein A (PAPP-A).
If the protein levels are either too high or low, it may be a
indication of a chromosomal mutation in the fetus.
b. Maternal Serum Screen
It is a blood test used to identify the risk of birth defect of the fetus at 15 to 20 weeks of pregnancy by screening the trisomy 18 for any abnormality.
2. Ultra sound
Ultrasound allows your doctor to visualize the fetus and around structures and to assess the abnormality the fetus.
3. Chorionic villus sampling
It is a type of of prenatal diagnosis to determine chromosomal or genetic disorders of the fetus with a test of a sample of the placental tissue before 15 weeks. In a sudy of Instruments
for chorionic villus sampling for prenatal diagnosis, by Zarko
Alfirevic, Peter von Dadelszen, researchers suggested that chorion can
be removed through the abdomen or through the cervix using fine
needles, plastic or metal tubes or biopsy forceps. The woman's risk of
miscarriage increases if several attempts are needed to get chorion,
or the gestational sac is damaged. The review found some evidence that
small forceps may be more effective and less painful than aspiration
cannulae for transcervical CVS. There were no trials found on
4. Amniocentesis (withdrawing a sample of the amniotic fluid).
Amniocentesis is a test of abnormalities of the fetus by
withdrawing a sample of amniotic fluid from a woman uterus and
examining it in the laboratory.
According to the Centers for Disease Control and Prevention (CDC),
approximately 3% of babies born in the United States will
have a birth defect. Family who is at higher risk or
previous birth defect incidence and have a family history of birth
defect, abnormality of the gene is identified in any test or the
pregnant mother is over the age 35 are beneficial for birth defect
According to the American pregnancy association, genetic counseling includes
1. Do you have a history of diabetes, hypertension, cancer, or twins?
2. Are there any diseases that seem to run in your family?
3. Is there a history of genetic disease like cystic fibrosis, hemophilia, or muscular dystrophy?
4. Is there anyone with mental retardation or any kind of birth defect?
5 Have any of your sisters, cousins, or other relatives had problems with their pregnancies?
6. Are your parents alive, and are they healthy?
7. What is your ethnic background?
8. Is there any reason that you suspect that your
baby may be born with a birth defect or other medical problem?
The aim of the evaluation is to determine the risk of your baby
will get from the disease and provide available options with the
family, depending to the data collection, including families risk,
interpretation of information, inheritance patterns analysis, risks of
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