Antenatal Screening

Antenatal screening is the way of finding out if the foetus had developed any anomalies or whether it will be developing any, in the course of pregnancy. Screening lets the doctors know how the abnormal conditions will develop in the unborn baby.

The mother should be subjected to pre-natal test if the risk of developing the anomalies is found to be very high. Some of the tests that may be administered to the mother are chronic villus sampling (CVS) and amniocentesis.

Need for antenatal screening

Antenatal screening helps in identifying a various number of genetic diseases that might affect the unborn baby such as:

• Sickle cell anemia
• Down’s Syndrome
• Spina bifida
• thalassaemia
• HIV
• Syphilis
• Hepatitis B
• Rubella

When should the screening be done

The screening tests are usually done during the early stages of pregnancy.

Blood tests are done during 11-20 weeks, to measure the protein as well as hormonal level, so that conditions such as Down’s syndrome or Spina Bifida could be detected.

Fetal anatomy test, carried out during 18-20 weeks of pregnancy, using ultrasound scan , helps in identifying if any heart problems exist, which could be treated as soon as the baby is born..

For the identification of Sickle cell as well as thalassaemia, screening must be done routinely.

Tests must be done on the mother for ruling out the chances of existence of the following:

• Anemia
• HIV
• Diabetes mellitus
• Thrombophilia
• Hepatitis B
• Urinary Tract Infections
• High blood pressure
  And
• Syphilis

Some of these conditions can cause too much of complications in the baby as well as mother. The infection in the urinary tract caused by bacteria known as Bacteriuria, results in the baby born prematurely or with under – weight.

Some of these tests are administered during the first antenatal appointment of the mother with the doctor. But some of the tests need to be undergone, only if the condition is really critical.

Use of antenatal screening

Antenatal tests usually provide the doctors with the knowledge on any anomalies the baby seems to develop. A diagnostic test is usually given to the mother, if it found out that the risk of the bay developing the anomaly is high. This prenatal diagnosis informs you about the anomalies the bay is likely to develop.

The mother is then convinced to take up the tests to rule out the risks. But there are cases where screening goes wrong. So the diagnostic tests help to confirm the existence of the anomalies.

Results

Screening tests are not diagnostic in nature. Its result is either positive or negative in nature. For example, if a screen test result is negative, it means there is no high risk involved, but that does not imply that problems can be ruled out.

The reliability of the test is done by comparing false-positive rate, (unaffected pregnancies wrongly identified having high risk) with detection rate (affected pregnancies identified rightly having high risk). Then if results are indicating chances of high risk, diagnostic tests must be taken.