Pregnancy is a very complicated process. Like any complicated process, there is always the chance something can go wrong; tests are available for detection of some of these problems. The presence of an abnormal number of chromosomes can occur such as trisomy 21 (Down’s Syndrome), trisomy 13, and trisomy 18 being the most common chromosomal anomalies in pregnancy. Fortunately these are rare but the risk increases with the mother’s age. Genetic conditions, such as cystic fibrosis, may also occur. Testing for these and other conditions is available if you wish.

 NUCHAL FOLD TEST:

  • Purpose: Screens for chromosomal abnormalities such as Down’s syndrome that can cause mental retardation and birth defects
  • What: Combination of an ultrasound and blood work
  • When: Between 11 and 13 weeks gestation.
  • Results: Recalculates the risk level for the baby having a chromosomal anomaly. Does not give a YES or NO answer but recalculates the risk level. For example, each woman has an underlying risk for her child having Down’s syndrome depending on her age or family history. The risk increases with age. For instance, a woman at age 20 has a 1 in a 1000 risk verses a women at 35 has a 1 in 250 risk for having a baby with Down’s Syndrome. The Nuchal Fold Test gives a new risk level that may be anywhere from 1 in 5 to 1 in 10,000.
  • Risks: None

QUAD SCREEN:

  • Purpose: Screens for chromosomal abnormalities and for neurotube defects. The Quad Screen recalculates the chance for chromosomal abnormality similar to the Nuchal Fold test. It also recalculates the risk for neurotube defects. Neurotube defects include spina bifida (incomplete fusion of the spinal cord) and anencephaly (incomplete development of the brain). A woman’s underlying risk for this, without a family history, is less than 1 in 1000.
  • What: Simple blood test
  • When: Between 15 and 17 weeks gestation
  • Results: Recalculates risk level for the baby having a chromosomal anomaly or a neurotube defect. Again, it does not give a YES or NO answer.
  • Risks: None

AMNIOCENTESIS:

  • Purpose: Many indications depending on when in pregnancy it is performed. Obtains fetal cells for chromosomal analysis to detect chromosomal or genetic anomalies. This is a diagnostic test.
  • What: Invasive procedure where a needle is introduced into the sac around the baby to obtain amniotic fluid and fetal cells.
  • When: Anytime after 14 weeks gestation through to the end of pregnancy
  • Results: Concerning chromosomal issues it is typically performed around 16 weeks gestation. This test will provide a YES or NO answer to chromosomal or genetic concerns. 
  • Risks: Unlike the screening tests above it does have a risk of causing a pregnancy loss of 1 in a 100 to 1 in 500 times.

CHORIONIC VILLUS SAMPLING:

  • Purpose: Obtain chorionic villi for chromosomal analysis to diagnose chromosomal or genetic abnormalities. This is a diagnostic test.
  • What: Sampling of placental tissue to obtain fetal cell.
  • When: Late first trimester
  • Results: Provides YES or NO answer to the presence of chromosomal or genetic concerns. 
  • Risks: This test has a 1 in a 100 chance of causing a pregnancy loss.

                       

 

       

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