Pregnancy Diagnostic Tests

Pregnancy is a period of anxiety – especially for the mother-to-be. Though a vast number of pregnancies are normal, the average rise in maternal age and lifestyle changes do pose a new set of challenges for today’s mothers.

But on the bright side, medical technology has advanced significantly and it is now possible to detect potentially serious problems in a developing fetus. Diagnostic tests during pregnancy can determine if a baby has, or will develop, a particular problem after birth.

When Do You Need Diagnostic Testing?

Doctors usually take many risk factors into consideration before advising a pregnant woman to undergo additional testing in pregnancy. These factors are:

  • Maternal age is in the mid-30s or older
  • A family history of a serious medical condition
  • Parents are “carriers” of a faulty gene
  • Having a previous child with a serious problem in growth, development or health
  • Exposure to chemicals or other environmental agents

But the decision to undergo diagnostic testing is a purely personal one. No one should be pushed into taking a diagnostic test as the results could have a considerable impact on the pregnancy. Before consenting to any procedure, make sure all your questions have been satisfactorily answered and the risk and benefit of each test has been thoroughly explained.

Common Diagnostic Tests In Pregnancy

Ultrasound
An ultrasound or sonogram test is recommended twice, in a normal pregnancy. The first ultrasound is usually done at 8-10 weeks to check for multiple pregnancies and to ascertain the due date. At 8 weeks, a detailed scan is performed to check for a range of physical problems.

One of the least-invasive forms of diagnostic testing, an ultrasound exam uses high-frequency sound waves to create a visual image of the fetus. During the scan, a special gel is applied to the woman’s abdomen and a transducer is placed on the belly to conduct the sound waves directly into the uterus. Pictures of the developing fetus can be printed or video recorded and given to the parents. Ultrasounds are very useful in detecting abnormalities such as Down’s Syndrome. When a problem is detected in an ultrasound, Doctors usually follow it up with other diagnostic tests.

Amniocentesis
A procedure in which amniotic fluid is taken from the uterus using a long needle inserted through the abdominal wall. Usually performed between the 16th and 18th week of pregnancy, this test is used to screen for genetic and chromosomal disorders.

An ultrasound exam is done before this procedure to determine the baby’s position and the location of pockets of amniotic fluid. Once the amniotic fluid is obtained, the cells are cultured and stimulated to grow for one to two weeks – when the cell chromosomes are examined and test results determined. Amniocentesis is usually prescribed for pregnant women aged 35 and older as they have an increased risk of having a baby with Down’s syndrome. It does carry a slight risk of miscarriage – so consider the risk/ benefit ratio before consenting to this procedure.

Chorionic Villus Sampling (CVS)
An alternative to amniocentesis, CVS helps detect genetic or chromosomal abnormalities. It can be performed earlier in the pregnancy (usually between the 9th and 13th week). CVS involves the sampling of chorionic cells (obtained either by placing a catheter through the cervix or through the abdominal wall) that can provide a complete picture of the genetic make-up of the developing fetus.

Non-stress Test (NST)
The fetal heart rate is observed through a fetal monitor and evidence of accelerations in the heart rate in relation to fetal movement is studied. This test is recommended when a woman notices a decrease in fetal movement or when the due date has passed.

Oxytocin Challenge Test (OCT)
Usually performed when results of the non-stress test are questionable, this test is very similar to the non-stress test, except that the woman is given a small amount of medication to induce uterine contractions. The purpose of OCT is to see how the fetus will respond to the normal stress of labour.

Bio-physiological profile
This involves an ultrasound examination of the fetus to determine the type of fetal movement and muscle tone that is present, along with the amount of amniotic fluid – to check for fetal well being.

Fetoscopy
An invasive test that involves inserting a lighted instrument through the abdomen and uterus into the amniotic sac, to observe and photograph the fetus. The risk of fetal loss is high and so, the test is indicated only for women who will benefit from having a fetal disorder identified and possibly treated during pregnancy.

Percutaneous umbilical cord blood sampling (PUBS)
This involves the removal of blood from the umbilical cord for further study. Performed under ultrasound guidance, PUBS makes it possible to detect several blood diseases not detectable by amniocentesis.

When a diagnostic test is recommended during pregnancy, it is important not to panic. Ask your Doctor to explain the reasons for testing, and getting all the facts right will actually help you overcome the anxiety.

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