- April 20, 2016
- Posted by: emobile
- Category: Uncategorized
Emibileclinic Trending Topic: Prenatal Diagnosis
Prenatal diagnosis is the process of ruling in or out fetal anomalies or genetic disorders, to provide expecting parents with information and the opportunity to modify pregnancy management and/or postnatal care.
Sickle cell Disease (SCD) is a genetic condition that is present at birth. It is the most common form of haemoglobinopathy in Nigeria affecting 1-3% of the population and it is associated with physical, psychosocial and emotional suffering.
Love they say is blind as couples with incompatible genotype still proceed to marrying each other in spite of the potential risk of sickle cell anaemia. It is interesting to know that one can know the genotype of the unborn child and prepare fully for whatever challenges might comes out. There is 3 out of 4 chance of a healthy child in each pregnancy for most couples at risk for sickle cell anaemia (e.g. AS x AS).
The availability of prenatal diagnosis (PND) for the disease has opened a window of opportunity for expectant couples to have information about the haemoglobin (Hb) genotype of their unborn child. This gives them the option of termination of the pregnancy in case of positive result and to prepare them psychologically, financially and medically for the arrival of the new child when abortion is not an option.
Chorionic Villus Sampling (CVS)
This can be done in the first trimester. DNA from the chorionic villi is studied to see if the baby’s genes for haemoglobin are normal, or if an alteration has been passed on from the parents. It takes from 3 to 10 days to analyze DNA.
DNA analysis is the best method for diagnosing inherited disorders. However in every medical test there is a small possibility of every medical test there is a small possibility of an error. The chance of a mistake is very small; less than 1 is 200 (0.5%).
There is practically no risk to the mother. The main risk is that the test could cause a miscarriage. We do the test as gently and expertly as possible, but anything that interferes with a pregnancy can cause a miscarriage. At the moment, the risk of miscarriage after CVS during the first 12 weeks seems to be around 1 in 50 (2%). How painful it can be losing a pregnancy of a child with genotype different from sickle cell.
Fetal Blood Sampling
This can only be done from 18-22weeks after the mother’s last menstrual period. The needle for obtaining the blood is passed through the mother’s abdomen to the baby’s umbilical cord without touching the baby.Fetal blood sampling is principally used either when the pregnancy is already far advanced or the placenta cannot be reached for CVS or when DNA analysis is not possible.
It is the easiest to perform of the 3 tests described here but because of the long process required in the laboratory before DNA analysis can be done, it is used only rarely when for some reason CVS or fetal blood sampling cannot be done.
It carries less than a 1 in 100 risk of miscarriage and virtually no risk at all to the mother. The result takes a minimum period of 3 weeks.
Pre-implantation genetic diagnosis (PGD)
Pre-implantation genetic diagnosis (PGD) involves removing mature eggs from the woman’s ovary. The eggs are then fertilised in the laboratory with sperm obtained from her partner or a sperm donor (if this option is chosen). The developing embryo (egg) is then tested for the genetic condition. If the embryo does not have the condition the fertilised egg is placed in the woman’s womb for a pregnancy to become established and continue. This process is often referred to as ‘in vitro fertilisation (IVF)’ or ‘test tube baby’.