Identification of Genetic Diseases in Pregnancy

Dear prospective parents,
The health of your unborn baby is one of the most important concerns during pregnancy. However, today’s advances in medical technology have enabled us to take detailed images of the fetus from the first weeks of pregnancy and offer many methods to monitor its development. Today, as in many modern health clinics, our center has pregnancy follow-up programs in the standards adopted by the world. In this way, the baby can be examined at certain stages of pregnancy to identify congenital mental and physical disabilities, especially those that are hereditary.
Genetic counseling
Expectant parents want to know as early as possible that their baby is genetically healthy. In pregnancies that need to be genetically monitored, first of all, an expert interview should be planned to determine the risks that the couple has, which tests should be performed in which periods and the results of these tests (genetic counseling). As a result of this meeting, the couple will have a genetic monitoring plan for themselves and their baby. Such planning is also psychologically comforting for the couple.
When genetic analysis of the unborn baby is necessary
Approximately 4% of newborns are born with genetic and non-genetic abnormalities. There is no cure for genetic diseases and their associated chromosomal abnormalities. However, prenatal diagnosis is possible. Approximately one in every 160 newborns has chromosomal abnormalities. Genetic screening is not necessary in every pregnancy. As a result of scientific studies, chromosome or gene analysis is recommended in pregnancies that are considered genetically risky according to the standards accepted today. Genetic analysis is recommended in expectant mothers younger than 35 years of age whose fetal development is normal during follow-up. The decision for pre-pregnancy genetic analysis should be taken with the advice of a specialist and, if necessary, couples should be given genetic counseling before the procedure. It should not be forgotten that, as with all genetic procedures, the family has the final decision. However, the family should be informed with accurate and sufficient information before this decision.
Genetically compromised pregnancies:
– Expectant mothers over 35 years of age
– Couples with recurring dreams
– Couples with an anomaly detected in the baby in a previous pregnancy
– Couples with a child with a genetic disease
– Detection of anomalies on ultrasonography monitoring during pregnancy
– Detection of increased risk in the first or second screening test
– Couples with a family history of a hereditary disease
Couples with any of the above characteristics are encouraged to seek genetic counseling to determine their genetic risk and the likelihood of passing it on to their baby, and to develop an appropriate genetic monitoring plan.
Indications for prenatal diagnosis
What is a chromosome
Chromosomes are the structures in our cells that carry genetic information, our genes. Our genes determine our appearance, growth and development. Normally, each of our cells has 46 chromosomes. Our children receive 23 chromosomes from the father through sperm and the other 23 from the mother through the egg. The risk of having an abnormal number of chromosomes in the egg increases with age.
Chromosomal disorders
Chromosomal disorders occur in approximately 0.5% of live births. Advanced maternal age is the most common indication for prenatal cytogenetic diagnosis. Although chromosomal disorders are seen in children of mothers of any age, the incidence of trisomic (three of one chromosome) children increases especially after the age of 35 for unknown reasons or reasons. Prenatal diagnosis should therefore be offered to all women who will be 35 years of age or older at birth. This age limit can vary and prenatal diagnosis is also offered to some young expectant mothers. Amniocentesis is recommended for women whose screening tests show an increased risk of carrying a fetus with Down syndrome (Trisomic 21) or Trisomic 18
Chromosomal abnormalities in the previous child are also an indication for prenatal diagnosis. If the couple has already had a live-born child with Down Syndrome and the mother was under 30 years of age at birth, the risk of the couple having another child with trisomy increases to 1%. If the mother is over 30 years old at birth, the risk is the same as the risk of advanced maternal age.
Recurrent spontaneous abortions may indicate a chromosomal disorder. In 50% of early spontaneous abortions, the fetus has a chromosomal abnormality. Recurrent spontaneous abortions are also an indication for prenatal diagnosis and examination of the chromosomal structure of the parents.
Risk of chromosomal disorders depending on maternal age
Mendelian inherited genetic diseases
Chorionic villus biopsy or amniocentesis is recommended in cases where both parents are recessive carriers of the same genetic disease (have already had a child with the disease or have been screened for carriage) and prenatal diagnosis of the disease is possible. Many genetic diseases such as cystic fibrosis, sickle cell anemia and huntington’s disease can be diagnosed prenatally. Not all Mendelian inherited genetic diseases can be diagnosed prenatally, but the number of diagnosable diseases is increasing day by day. For high-risk patients, amniocentesis, chorionic villus biopsy, fetal blood or skin biopsy or ultrasound can be used.
For some specific genetic diseases, such as sickle cell anemia, certain ethnic and geographic populations can be screened for carriage through prenatal testing. Screening of newborns can also identify couples who are carriers of certain metabolic diseases. For other couples with autosomal dominant or X-linked recessive disorders, family history can be used. A physical examination of the couple can also help find a Mendelian inherited disease.
How genetic analysis is performed on the unborn baby
The baby’s own genetic structure cannot be determined by looking at the samples taken from the mother and father, because the baby is a genetically different individual formed by the rearrangement of some genetic features taken from the mother and father. Reaching the fetal tissue required for genetic analysis requires external intervention, even if it is small.In cases where the test is required, genetic analysis is performed by taking amniotic fluid, chorionic villus biopsy or fetal blood from the womb or birth canal at the appropriate gestational weeks. No anesthetic or pain medication is required during these procedures. After the procedure, there may be roughly one in a thousand to one percent of infant loss or other complications (such as infection) related to the procedure. Depending on the gestational weeks, it is possible to obtain the necessary material in several different ways without harming the baby.
Chorionic villus biopsy
It is the sampling of the fetal part of the placenta with the help of ultrasound at 10-12 weeks of gestation. This method allows the genetic makeup of the fetus to be determined in the early weeks of pregnancy.
Amniocentesis
Classically, some of the amniotic fluid is removed from the gestational sac between the 16th and 18th weeks of pregnancy. The fetal cells in this fluid can be used for multiple tests.
Fetal cord blood analysis
This method is used in late gestational weeks when it is too late for amniocentesis, for a possible genetic diagnosis or to detect blood disorders. In addition to these methods, there are other methods such as fetal skin biopsy and fetal liver biopsy for advanced and specialized diagnoses.
Preimplantation pregnancy diagnosis (PGD)
PGD is a genetic analysis method that has been used for the last 10 years. With this method, embryos of genetically risky couples can be analyzed before pregnancy occurs and healthy and sick embryos can be selected. This way, healthy pregnancies can be achieved by transferring only normal embryos to the mother.
What we can learn about the baby’s genetic structure
In prenatal genetic analysis, which we call prenatal diagnosis, anomalies that we think the baby is at risk are investigated. For example, in a baby at risk of Down Syndrome, chromosome analysis is performed to examine the number and structure of chromosomes the baby has. In a baby who should normally have 46 chromosomes, for example, a baby who should have chromosome 21, for example, if chromosome 21 is seen in one more than two samples from one mother and one father (three chromosomes 21), Dow Syndrome, which can cause severe mental retardation and physical freedom, emerges.
For single-gene disorders that we know can be life-threatening, for example, beta globin gene analysis in a fetus with a family history of Mediterranean anemia can be used to determine whether the baby has the disease. In our country, it is unethical and illegal to genetically examine a fetus for a disease that can be life-threatening and does not cause serious mental or developmental retardation. It is technically impossible to determine the entire genetic structure and all genetic diseases that may be encountered from a sample taken from the fetus. Likewise, low rates of mosaicism (the coexistence of at least 2 cell lines with different genetic makeup) and microdeletions or duplications, which can only be shown with special techniques and staining, cannot be analyzed with these tests.
New developments
Microarray Screening
Thanks to ‘Microarray’ technology, which is a product of the interaction of developing technology with genetic science, more than 100 genetic diseases can be analyzed in a single experiment. VKV American Hospital Genetic Diseases Diagnosis Center offers Microarray technology service to expectant mothers and couples when necessary.
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