Special Tests During Early Weeks Of Pregnancy

Dec 03, 2010 No Comments by

Your blood will have be tested at your booking -in appointment to determine your blood group and to establish its rhesus (Rh) status. The rhesus status of your blood depends on whether or not it possesses the rhesus factor. If the factor is present,  your blood is Rh-positive, and if it’s absent, your blood is Rh-negative. Most people’s blood is Rh-positive.

If both you and the baby’s father are Rh-negative, there is no  problem. complications will only occur when the father blood is Rh-positive and your is Rh-negative. The unborn baby may acquire the rhesus factor from its father, which can result in its blood being  incompatible with yours. This can lead to a serious or even fatal illness for the baby before, or after the it’s birth.  Fortunately, this rarely affects a first pregnancy and it can be  prevented in subsequent pregnancies by injections of anti-D gamma globulin, an antibody that may be given during pregnancy and again within 72 hours of a baby begin delivered.

AFP Test

At around  week 16 you are likely to be offered a test to check the level of alpha feto protein (AFP) in your blood. If your AFP level is unusually high, it may mean that your pregnancy is more advanced than you thought;  or that you are expecting twins; very rarely it indicates that the baby may have spina bifida or related conditions. A lower than usual AFP level may mean that the pregnancy is less advanced; or in a few cases, that the baby has down’s syndrome.

Special Tests

There are a number of ante-natal tests that are used if there  is some fear of genetic abnormality. They include:

1. Amniocentesis. If you have a family history of genetic abnormalities or your blood shows a high or exceptionally low AfP level, you will be offered an amniocentesis. This test is also offered an amniocentesis. This test is also offered to all woman over 35 years as they have a higher risk of having a down’s syndrome baby. Guided by an ultrasound scan, a long hollow needle is  inserted through the wall of the abdomen and the uterus to draw out a sample of amniotic fluid which is tested for abnormalities. The test carries a small risk of miscarriage.

2.Chorionic Villus Sampling (CVS). CVS is done at 11 weeks to test for down’s syndrome or other genetic or chromosomal abnormalities. A fine tube is passed into the uterus to remove some cells from the tissue that surrounds the baby. the cell are then tested and the results known within a couple of weeks. The advantage of  CVS is that if there is a problem, a termination can be done early in pregnancy. there is a slightly higher risk of miscarriage with CVS than with amniocentesis.

3.Nuchal Translucency Measurement. This test for down’s syndrome is carried out at 10-14 weeks. Using ultrasound, the fluid space at the back of the fetus’ neck is measured. By combining this measurement with the mother’s age and hormone level in her blood, the risk of down’s syndrome can be  calculated. A positive result is followed by a diagnostic test such as CVS or amniocentesis.


4.Cordocentesis. This test is done to confirm diagnosis of chromosomal abnormalities and diseases such as rubella and toxoplasmosis. A hollow needle is inserted through the abdomen into the umbilical vein, close to the placenta, and a sample of the baby’s blood is withdrawn. It is only performed after 18 weeks when the blood vessels are large enough.

Genetic Counselling

If you are worried about your children inheriting a disease or handicap, you can talk to the genetic counsellor. Counselling is based on details of diseases that run in the family or a chromosome analysis from a blood sample.  The counsellor will be able to explain the likehood of future children being affected by the disorder and also about any tests that can be carried out. It is a good idea to have this discussion before attempting to get pregnant so that you know what is involved.


Conception, From Conception To Delivery
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