Amniocentesis During Pregnancy

Testing for Birth Defects or Abnormalities

The choice to have an amniocentesis - which is a test for birth defects or abnormalities - during pregnancy is a big decision that shouldn't be taken lightly.

What is Amniocentesis?

Amniocentesis is a test performed on a pregnant woman to determine if her unborn child has any birth defects or abnormalities. Generally the test is performed on women older than 35 as the older a woman is during pregnancy, the higher the risk of genetic abnormalities to the fetus.

Just recently, studies have suggested that this age limit be moved to 40 and the test be performed earlier only if other screening methods suggest amniocentesis would be beneficial. Amniocentesis can also be performed on a woman no matter her age if she is a carrier of, or has a family history of, genetic abnormalities such as cystic fibrosis or Huntington's disease.

Amniocentesis is performed after the 14th week of pregnancy. Prior to that, the test is not as accurate and carries a higher risk of miscarriage. Results of the test take 1 to 3 weeks.

How is Amniocentesis Performed?

An ultrasound shows where the baby is inside the amniotic sac. A long thin needle is inserted through the mother's abdomen and into the uterus where a small amount of the amniotic fluid surrounding the baby is withdrawn for testing. The amniotic fluid contains cells that the fetus has shed. These cells contain the genetic makeup of the baby, giving a clear picture of any genetic abnormalities.

What Can an Amniocentesis Tell You?

Amniocentesis can determine if the fetus has any of more than 100 birth defects including Down Syndrome, spina bifida or anencephaly. Amniocentesis can also detect the Rh compatibility of mother and child. Amniocentesis does not detect all abnormalities. For example, the test will not show if the developing baby has a cleft palate. An amniocentesis can also determine if the baby's lungs are developed enough should delivery need to occur before the baby is full term.

Why Have an Amniocentesis?

A woman may choose to end her pregnancy after amniocentesis shows the fetus is severely disabled or unhealthy. Some women choose to have the test in order to prepare themselves for any challenges their child may be born with. Results indicating abnormalities can help decide any medical intervention that could occur in utero or immediately after birth. And many women willingly choose not to have the test at all despite any increased chances of delivering a child with birth defects.

Risks of Amniocentesis

Amniocentesis does carry some risks to the unborn child. There is a 1 in 200 chance of miscarriage (some information suggests this is as low as 1 in 400). There is a risk of infection to the amniotic sac. The mother may experience vaginal bleeding, cramping or discomfort after the procedure. If the mother 's blood is Rh negative and her fetus is Rh positive there is risk of Rh sensitization. There is very little risk of the needle used during the procedure actually hurting the fetus.

Amniocentesis is a personal choice. Ask yourself how you would feel knowing your unborn child has a birth defect. Think about how you would feel if it was a surprise at delivery. How will you cope with the news either way? Would you continue the pregnancy? What would change for you in the last trimester knowing that your child will be born with a birth defect? Speak to your doctor or midwife about amniocentesis and get as much information as you need to feel comfortable with your decision.

For more in depth reading see Amniocentesis.