An important consideration for mothers-to-be when preparing for pregnancy is the numerous types of health conditions that may be passed down from parents to their children, also referred to as genetic disorders. Fortunately, a new examination technique called “preconception gene testing” is now available. Utilizing new technology as part of the precision medicine concept, this technique is able to screen and diagnose conditions at the genetic level. If a disorder is identified, the faulty gene can be stopped in its tracks before it is passed onto the next generation. Preconception gene testing has a very high accuracy. It is capable of identifying more than 600 recessive genes that are responsible for causing over 200 genetic disorders.
The number of genetic disorders – of which parents may be carriers and which can be passed down from generation to generation – is huge. The following conditions are the most common disorders found in both Thai and foreign nationals:
There are still many more genetically transferable disorders besides those mentioned here, which are all caused by chromosomal or genetic abnormalities that lead to irregularities in the various systems of the body. These conditions may affect the functioning capabilities of certain bodily systems or organs and are referred to in the field of medicine as “systemic diseases”.
These are categorized into the following groups, according to their symptoms:
This group of disorders is caused by an irregularity in the 21st pair of chromosomes. Specifically, an extra chromosome strand is present when compared with the chromosomes of normal babies. The incidence of Down Syndrome is higher in older mothers, especially those who are older than 35 years. Children born with the condition will suffer from mental disabilities that will require special care and treatment. They will also suffer from physical developmental issues, as well as abnormalities in organ functioning, such as heart defects.
Another chromosomal irregularity, Edwards syndrome affects the 18th pair of chromosomes. Again, an extra chromosome strand is present when compared with other newborns. This disorder is the second most common chromosomal abnormality after Down syndrome, with 1 out of every 3,000 newborns affected. Children with this condition will have severe mental disabilities and suffer from disorders that affect their vital organs, such as heart, brain and kidney defects. Additional symptoms may also affect other parts of the body, for example, microcephaly, cleft lips, cleft palates or a club foot. Generally, children with this condition do not survive through pregnancy or they may live for just a few weeks after birth. The older a mother is when pregnant, the greater the chance that her child develops this group of conditions.
Patau syndrome is a condition caused by irregularities affecting the 13th pair of chromosomes. Children who suffer from this condition will have severe mental disabilities in conjunction with complicated organ defects. Children with Patau syndrome tend not to survive through pregnancy or for more than a few weeks after birth.
This disorder is caused by a fault in the X chromosomes. Specifically, there are fewer chromosomes than usual. Children with this condition tend not to survive through pregnancy or will be born prematurely. However, survival is possible if the condition is properly treated. Their physical development may also be affected. Children with this condition tend to be shorter than other children. Children with Turner syndrome also find it hard to conceive and require hormone treatment for the duration of their lives.
A disorder that is exclusive to males, Klinefelter’s syndrome is also caused by faulty X chromosomes. For this condition, there are more of chromosomes than usual. Patients with Klinefelter’s syndrome will have smaller testicles than normal and will experience difficulty conceiving. They may also suffer from other physical abnormalities, such as being abnormally tall and having large breasts.
Genetic screening to identify hereditary conditions that may be passed on to the next generation is carried out by specialists in the field of reproductive medicine. The screening can assist parents who wish to undergo IVF treatment. Because in addition to aiding the embryo selection process, the screening can also be combined with other forms of testing to increase the likelihood of success in reproduction. These tests include a uterine receptivity test, which analyzes the readiness of the womb for fertilization, as well as preimplantation genetic screening (PGS) or Preimplantation Genetic Testing for Aneuploidy (PGT-A), which utilizes next-generation sequencing (NGS) techniques.
PGS or PGT-A is an embryo screening technique that analyzes the chromosomes and various genes to identify any potential abnormalities before screening for no aneuploidy embryos that are suitable for implantation back into the womb. The process helps ensure that mothers give birth to a normal chromosome child, as the process is highly accurate, giving the predicted results up to 95% of the time.
Consulting with a doctor to receive appropriate care and advice on how to plan a pregnancy is therefore of huge importance for married couples. It is recommended that couples attend such a consultation around three months prior to conception. Even for mothers-to-be who are young enough and able to conceive naturally, a general health examination should still be carried out before conception. In this way, any information related to the genes of the parents can be used to help analyze the risks of a genetic disorder being passed onto their children, as well as to find out whether or not the parents are carriers of any genetic conditions without knowing it.
Diploma Thai Board of Obstetrics and Gynecology Faculty of Medicine Vajira Hospital, Navamindradhiraj University , 1995