A Groundbreaking discovery: Fetal DNA in Maternal blood

In 1997, chemical pathologist Dennis Lo, now at the Chinese University of Hong Kong, discovered that roughly 10% of the total volume of DNA in a sample of maternal blood was from the baby she was carrying. This discovery has changed and is still changing the face of prenatal testing as we know it. Several studies are being carried out by leading universities and laboratories around the world. The genetic sequence of the unborn baby can now be mapped by simply taking a blood samples and thus, there is no longer the necessity to resort to risky, invasive fetal DNA sampling methods.

The use and the future of invasive sampling methods

Invasive sampling methods for collecting samples of fetal DNA include amniocentesis and chorionic villus sampling. Both these methods are still very much in use today, helping doctors establish the genetic health of the baby and allowing parents to know whether their baby is carrier of any genetic diseases, neural tube defects and chromosomal abnormalities.

Amniocentesis requires an OBGYN to insert a needle into the womb so as to extract a fixed quantity of amniotic fluid (usually around 20ml). To ensure the needle is inserted into the correct place and does not come into contact with the baby, the specialist uses ultrasound imaging.

Chorionic villus sampling is done in one of two ways. The OBGYN can either insert a catheter through the cervix and into the womb or else, they can insert a needle through the abdomen, always guided by an ultrasound. Whilst amniocentesis requires the extraction amniotic fluid, chorionic villus sampling involves extraction of a section of tissue known as the chorionic villus.

These types of sampling all have risks which can include permanent damage to the baby’s limbs and miscarriage. Since collecting fetal DNA from maternal blood is entirely a risk free procedure, scientists are working hard to maximize its uses so that any invasive sampling procedure like amniocentesis and chorionic villus sampling will no longer be required in future. Diseases, including neural tube defects, chromosomal abnormalities and hereditary illnesses will be diagnosed by extracting samples of maternal blood just as happens with any other blood draw.

What else have scientists discovered?

The analysis of samples of pregnant mother’s blood has revealed two different types of fetal DNA. The first type is cell-free fetal DNA, which basically consists of DNA fragments which have been released from the boundaries of the cell wall. Maternal blood samples also contain nucleated DNA (in this case, the DNA is still enclosed within the cell). Whilst fragments of fetal DNA (cell-free DNA) get flushed out of the mother’s body quickly and thus, persist for a very short time in the maternal blood, nucleated fetal cells can persist for years in the mother’s peripheral blood stream.

Prenatal Testing for Paternity

Whilst in the past getting a DNA sample from an unborn baby entailed the risks associated with amniocentesis and chorionic villus sampling, nowadays this is no longer the case. Non invasive prenatal testing makes it possible to carry out a paternity testing in the earlier stages of pregnancy by extracting a sample of maternal blood. Due to the presence of fetal DNA in the maternal blood sample, scientists can extract the genetic blueprint of the fetus and compare it to that of the alleged father. Besides being risk free, sampling for non invasive prenatal paternity testing can be carried out earlier than sampling using other methods such as amniocentesis and chorionic villus sampling.

About the Author:

The above article is written AJ who is associated with many health communities and blogs as their freelance writer.

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