As medical science has advanced, it is now possible to know a number of things about your baby even before they are born. A series of prenatal tests are carried out during specific periods in pregnancy for screenings of various types. These tests are aimed at discovering if everything is normal with your baby. The result is that you can make informed decision about the future and prepare yourself for it. However, there are a number of ethical and social issues involved in it and there are some arguments that prenatal tests should be kept to a minimum.

Every mother is concerned whether the baby she is carrying is healthy or not. In older times mothers had to wait till the baby was born to find out if they were healthy or not. However, with the advancement of medical science, a series of non invasive prenatal tests have been developed to find out whether the baby is healthy and the pregnancy is progressing normally.

Importance of prenatal tests

Prenatal tests serve a number of purposes. These are as follows:

  • You will know whether your baby is healthy or not and whether the child growth is satisfactory. Anxiety and mood swings are common in pregnancy. Positive results of such tests can help you cope with your pregnancy better.
  • If you or your partner have a family history of some genetic disorder, prenatal testing can help you determine whether your child is going to inherit the condition as well. This can help you prepare better for the future.
  • Finally, certain maternal conditions make prenatal tests compulsory. For example, if the mother is a known carrier of HIV, prenatal tests are absolutely indispensible.

Some considerations before prenatal tests

Though prenatal tests are largely noninvasive, you are still going to undergo considerable poking and prodding. You have to understand what the purposes of these prenatal tests are and whether you really need them.
Here are some considerations:

  • Would the tests prepare you to be better parents?
  • Are you intellectually and emotionally capable of making informed and rational decision about your baby?
  • If the test results turn out something negative, are you ready to face the consequences and take some wrenching decisions?
  • Are you willing to take the risk that one of the test results may be wrong?
  • Is it worth it to take the risks like pain or possibility of miscarriage to carry out the tests?
  • Is it feasible for you to bear the expense of the tests? Bear in mind that coming of a baby is accompanied with a host of expenses and you have to decide which ones you can afford.

Prenatal testing should not be done merely to satisfy an idle curiosity. They are medical tools and should be used with care. Moreover, there are social and ethical arguments against these types of testing. It is said that those who have economic power will get all the tests done and will be able to eliminate any fetus with likelihood of future problems. On the other hand, poorer section of society will not be able to afford these tests and will have a larger proportion of babies with inherited problems.

Common prenatal tests

There are two broad categories of prenatal tests. These are as follows:

  • Screening tests are those which are used to identify if your baby is more likely to have certain conditions. However, they offer a probability in diagnosis; not a certainty. They pose no danger to the mother or the baby.
  • Diagnostic tests are those which are carried out if one of the screening tests suggests high likelihood of a problem. If the screening tests combined with your medical history suggest a problem, a diagnostic test is carried out to confirm it. Some of these tests may carry health risks or a risk of abortion.

The most common prenatal tests are:

  1. Tests are done to check the levels of HCG (human chronic gonadotropin) hormone. High levels of this hormone may suggest multiple fetuses. It may also indicate that the fetus has a probability of developing Down's syndrome.
  2. Alpha-fetoprotein or AFP screening is a standard prenatal test. This test is done to detect if the fetus has defects in the neural tube spina bifida where the spine is deformed or anencephaly or part of the brain may not be formed.
  3. AFP and HCG are tested along with estriol in triple screening while inhibin is added in the quad marker test to increase the accuracy. Both the triple screening and the Quad marker test try to find out about neural defects and possibilities of Down's syndrome. If the mother has low levels of AFP and estriol combined with high levels of HCG and inhibin, her fetus is at greater danger of developing Down's syndrome and diagnostic tests are indicated.
  4. Ultrasounds are highly effective in visually assessing if the baby has any deformity. The sex can also be determined.
  5. Glucose screening is a must in all pregnant women because 3% to 5% of women develop gestational diabetes.
  6. Amniocentesis is another prenatal test. If the expectant mother is above the age of 35 and her screening tests indicates that her fetus has a greater likelihood of birth defects, she has to undergo this test. A small amount of amniotic fluid is removed for testing.
  7. Chronic Villus sampling or CVS serves the same purpose but it can be done earlier so that pregnancy can be terminated earlier if needed. It is also done if there is not enough amniotic fluid for amniocentesis.
  8. Cordocentesis or fetus blood sampling is a test where sample of blood is collected from the umbilical cord. It helps to detect if the fetus has developed anemia and whether the immune system of the mother is reacting unfavorably towards the fetus.

The different prenatal tests are carried out at different times of your pregnancy. These are as follows:

First trimester
  1. Blood tests
  2. Urine tests
  3. Chronic villus sampling
  4. Ultrasound
Second trimester
  1. Maternal serum Alpha-fetoprotein and multiple marker screening
  2. Ultrasound
  3. Glucose screening
  4. Amniocentesis (optional)
  5. Cordocentesis (optional)
  6. Fetal Doppler ultrasound
  7. Fetoscopy (rare)
Third trimester
  1. Group B streptococcus screening
  2. Electoral fetal heart monitoring
  3. Nonstress test (for high risk pregnancies and overdue babies)
  4. Contraction stress test (high risk pregnancies)

Brief descriptions of the above tests are:

  1. Blood tests
    The blood type and Rh factor is determined. These tests are also used to check for rubella, hepatitis B, syphilis, HIV and other sexually transmitted diseases. Risks foe sickle cell anemia and exposure to varicella are determined.
  2. Urine tests
    This is the basic test to detect pregnancy. Once it is confirmed, urine tests may be done to check your kidney function, diabetes or albumin. The presence of the last indicates high blood pressure induced by pregnancy.
  3. Chronic villus sampling (CVS)
    This is an optional invasive test generally done if the mother is above 35 years and there is family history of defects like Down's syndrome, cystic fibrosis, hemophilia or muscular dystrophy.
  4. Maternal serum alpha-fetoprotein (MSAFP) or multiple marker test
    It is used to detect the possibility of existence of Down's syndrome or neural tube defects.
  5. Triple test and quad test
    The triple test is that where human chronic gonadotropin (HCG), maternal serum alpha-fetoprotein (MSAFP) and estriol hormone are checked together. When inhibin is added, it is quad marker test. These tests detect 75% of neural defects and 75% to 90% of Down's syndrome. 3% to 5% of women have abnormal reading but many are false positives.
  6. Ultrasounds
    These are used for various purposes ranging from assessing the due date, detecting abnormalities like a cleft palate, low lying placenta etc.
  7. Glucose screening
    If you develop gestational diabetes, it can give rise to your health problems as well as other complications like too large baby and difficult delivery. Blood sugar level is tested an hour after drinking a special soda.
  8. Group B streptococcus screening
    The Group B strep is leading cause of life threatening infections in infants, hearing problems, mental defects etc. so, the mother is tested. 30% of healthy women carry Group B streptococcus. They are given antibiotics.
  9. Electric fetal heart rate monitoring
    This is done during labor and delivery. It indicates if delivery is going on schedule or if the baby is in trouble.
  10. Nonstress test
    Fetal monitor is strapped across the abdomen of the mother to measure the heart rate of the baby as it moves. It is carried out in multiple fetuses and high risk pregnancies.
  11. Contraction stress test
    If labor is induced by oxytocin or nipple stimulation, this test is done to determine whether these measures are affecting the baby and whether she can cope with the stress of labor.