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Why are tests done?

Here's all you want to know about tests during pregnancy

CARING Periodical monitoring

Sunanda is excited and a bit apprehensive. Her home pregnancy test has confirmed what her husband and she were hoping would be true. She is finally pregnant! She has scheduled an appointment with her obstetrician. She has been calling all her friends to find out what she will be facing at her appointment. She has been told that she will be undergoing a physical examination and then will have some tests done.

Tests during pregnancy

During pregnancy, certain lab tests are done on all women. These tests can help the gynaecologist spot possible problems during the pregnancy. Some tests are to see how the baby is faring. Other specific tests may be done depending on the medical history and family background.

Initial lab tests

A number of lab tests are recommended for all women in pregnancy. Some of these are done to diagnose certain problems during the pregnancy. Others do not diagnose problems — they are done to see if the mother or the baby is at risk of certain problems or birth defects. These are called screening tests.

Urine test

The urine will be tested at each prenatal visit. This test checks the levels of sugar and protein. Often, sugar in the urine is normal in pregnancy. High levels of sugar could be a sign of diabetes. Protein in the urine may be a sign of urinary tract infection, kidney disease, or high blood pressure that occurs in late pregnancy. If these problems occur, they can be treated.

Blood tests

Blood group and antibody screen — the blood group could be A, B, AB, or O. It can be Rh positive or Rh negative. If the blood is Rh negative, an antibody screen will be done periodically during the pregnancy. It is important to know if the blood is Rh negative because if the mother is Rh negative and the baby is Rh positive, a special immunoglobulin injection has to be given to the mother after the delivery to prevent problems in the next pregnancy.

Haemoglobin and haematocrit levels in the blood are measured to check for anaemia.

Syphilis is a sexually transmitted disease and it is mandatory to test for it because it can be passed on to the baby if not treated. Hepatitis B virus infects the liver and can persist in the blood for many years.

This virus can be transmitted to the baby during delivery. If present in the mother's blood, the baby will be given an immunoglobulin injection and a vaccine at birth to prevent it from getting the infection. Human immunodeficiency virus (HIV) is the virus that causes AIDS (acquired immunodeficiency syndrome). Pregnant women are tested even if they do not have special risk factors. If the test comes back as positive, certain steps have to be taken to reduce the risk of transmission to the baby.

Glucose screening is a test for diabetes in pregnancy. The patient drinks a special glucose drink and an hour later, a blood sample is drawn to measure the level of glucose in the blood. This is usually done between 24 and 28 weeks of pregnancy.

Ultrasound

An ultrasound exam is a test that creates an image of the foetus using sound waves. An ultrasound exam may be done to know the age of the foetus, follow the growth of the foetus and to look for physical abnormalities. The first exam is usually done in the third month. The scan done between the fifth and sixth month is very important because it can pick up physical abnormalities. Further scans may be done at the discretion of the obstetrician.

Screening for Down's syndrome

Down's syndrome is the commonest cause of mental retardation in children. This can occur in women of any age though the risk increases after the age of 35. The two tests for Down's syndrome are first trimester screening, done at 11-14 weeks or triple screening, done at 15-21 weeks.

The first trimester screening combines the baby's nuchal translucency (measured by ultrasound) with blood tests in the mother for human chorionic gonadotropin (HCG) and PAPP-A. Triple screening measures the levels of the hormones estriol, HCG, and alphafetoprotein (AFP), in the mother's blood. The results come back in 1-2 weeks. The result will tell us if there is a risk of the baby having Down's syndrome. If the screening test for Down's syndrome comes back as positive, further tests will be done to confirm whether the foetus really has Down's syndrome. Amniocentesis (testing the fluid from around the foetus) is the usual test done to confirm or rule out if the foetus has Down's syndrome.

GITA ARJUN

(The author is a Chennai-based obstetrician and gynaecologist with a special interest in women's health issues)

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