Amniocentesis & Chorionic Villus Sampling & PUBS


These three methods of fetal DNA sample collection are referred to as being “invasive”. The term invasive is medical and is used to refer to the fact that breakage or rupture, skin break, of internal body cavity or mucosa. Something which cannot be avoided with all three methods.

Chorionic villus sampling can be carried out between the tenth and the twelfth week. The name, chorionic villus sampling, refers to type of sample collected; the chorionic villi are little projections lining the womb which increase contact with the maternal blood supply. The sample for this test can be collected by inserting a catheter through the cervix or by insertion of a sterile needle through the abdomen.

Amniocentesis is carried out starting at fifteen weeks. The OBGYN will in this case insert a sterile needle into the womb and proceed to extract around twenty milliliters of amniotic fluid. This fluid is rich in dead fetal cells, from which laboratory analysts can extract the baby’s DNA profile. The procedure takes anywhere between five to ten minutes excluding the ultrasound needed prior to sampling to determine the position of the baby and ensure the needle is inserted into the correct place.

Both these two discussed sampling methods entail certain risks. About one in every hundred women who undergo these, miscarry the baby they are carrying.

Once samples have been collected, the child’s genetic profile can be mapped and used for a paternity test (or in many cases to confirm the fetus’s genetic health). Due to the risk of miscarriage however, some women chose to hold off from prenatal paternity testing opting instead to carry out the test once the child is born. Post-natal paternity testing is entirely risk free as the DNA sample can be collected by rubbing an oral swab inside the mouth of the new born and sending this off for analysis.

Paternity testing after birth

If a paternity test is carried out following the birth of a child, sample collection is simple. Oral swabs in such an instance are the quickest way of collecting samples. All you need to do is rub the swabs inside the mouth of the child for a couple of seconds so as to collect a sample of check cell from which the DNA will be extracted. However, if the baby is still in the womb collecting a DNA sample will not be so simple.

Paternity is a much disputed domain. The number of paternity tests carried out each year in the USA alone runs into several tens of thousands of tests. The paternity of a child can be established before birth in a prenatal paternity test or after birth. Paternity testing whilst pregnant is rather more complex as it requires entirely different DNA sampling procedures. Visit our Faqs for more information about invasive and non invasive prenatal paternity testing.