Should I have an amniocentesis?

By Elizabeth Stein, CNM

Question
I am 35 years old and pregnant with my first child. My doctor suggested I have an amniocentesis but I am confused and scared. What should I do?

Answer
Amniocentesis is a procedure done during the early part of the second trimester of pregnancy (usually between 16 and 18 weeks). The pregnant woman lies down with her abdomen exposed. Ultrasound (sonogram) is used to show the doctor where the baby and placenta are located and where to safely insert the needle. The needle is inserted through the abdomen and the uterus into the amniotic fluid that surrounds the fetus. A small amount of the fluid is withdrawn -- approximately one ounce (30cc). This amniotic fluid contains cells from the fetus that can be tested. These cells have the same genetic makeup as the fetus. The patient may feel pressure but very little pain with amniocentesis, but it may cause a lot of anxiety.

Who should have one?
Any pregnant woman who:

• Will be 35 years or older at time of delivery (chromosomal abnormalities increase with a woman's age)
• Has a history of a previous fetus or child with a birth defect
• Has a family history of certain birth defects
• Has an abnormal genetic test (such as MSAFP) or abnormal sonographic results from this pregnancy

But is the information obtained from the procedure worth the risk? What will you do with this information?

A few scenarios may help clarify the decision-making process:

1. A woman states that she accepts whatever baby God gave her and would never terminate. This woman may not want to take the risk that amniocentesis entails, since she will continue her pregnancy, no matter what the results are.
2. The same woman lives in an isolated area far from a high-risk/tertiary care hospital. She might consider amniocentesis so that if an abnormality were diagnosed, she could arrange to deliver her special-needs baby at a high-risk/tertiary care hospital. Although this might involve a scheduled induction or cesarean delivery, the pediatric specialists would be on-call or present to care for her newborn. The information obtained from amniocentesis would also give her time to prepare herself for parenting a newborn with special needs. She may need to consider physical, psychological, emotional, and financial issues, and locate a pediatrician or surgeon qualified to care for her newborn. She'll need to coordinate help at home and plan for special care and education in the future.
3. Woman states she only wants a normal baby, would terminate the pregnancy if the baby has a chromosomal abnormality, such as Down syndrome. This woman will probably accept the risk inherent in amniocentesis, since her need to know that her fetus is normal is very great. The information obtained by amniocentesis would be a great part of any decision-making process. These choices are time sensitive. Because amniocentesis is usually done at 16 to 18 weeks, and the results take two to three weeks, abnormal results need to be discussed and choices and options reviewed. She might need to consult with others such as pediatric or surgical specialist or genetic counselor. Termination is legal up to the 24th week of pregnancy, but in many institutions the limit is less than 24 weeks; earlier termination carries less risk for the woman.
4. A woman has a sonogram that reveals an abnormality (i.e., omphacele, nuchal thickening) that may be isolated, or that may be associated with other abnormalities. This woman might need more information in order to make a decision, and an amniocentesis would provide that information.
5. A woman simply can't decide what to do! A woman who can't decide could consider worst-case scenarios: Which would be worse for you to live with? To deliver and have to care for a baby with an abnormality that you didn't expect, or to lose a normal pregnancy?

What are the benefits of amniocentesis?
The "need to know" question is answered.

The results obtained from amniocentesis are diagnostic. Although it takes two to three weeks to get the results, hearing that your baby is "chromosomally normal" is a great relief. It answers the question: Does my baby have Down syndrome or other chromosomal, genetic, or neural tube defects? It does not test for every known abnormality, including a structural abnormality such as cleft palate. Testing for specific conditions should be addressed with your midwife, doctor, or genetic counselor.

If the results do identify an abnormality, this information can be used to help you make important decisions. You'll want to

Consider where to deliver your newborn (a baby with certain known conditions should be delivered in a high-risk/tertiary care hospital that is prepared to care for your newborn's special needs; otherwise your baby might need to be transferred to another hospital while you are still postpartum!)

Consider being referred to a pediatric or surgical specialist to discuss what future issues and choices you may have to face -- even whether you want to continue your pregnancy or terminate it.

What are the risks of amniocentesis?
Basically, the greatest risk is loss of the pregnancy. The chance of this happening is statistically 1:200, meaning one woman out of every 200 who have the procedure will have leakage of amniotic fluid that cannot be stopped or develop an infection and lose the pregnancy, which could have been a normal fetus. This risk is per fetus -- each fetal sac entered with twins or triplets carries its own risk. Loss of one fetus usually causes the loss of all fetuses. If an infection develops, the pregnancy will have to be terminated since infection would risk the mother's life.

Diagnosing an abnormal baby versus losing a very much wanted pregnancy (abnormal or normal) is like comparing apples to oranges. How can a woman decide what to do, when 199 out of 200 procedures are uneventful, but her own loss would be a 100 percent disaster to her?

The good news
The vast majority of amniocentesis procedures are uneventful and the results indicate a normal fetus.

Thoughtful consideration of possible abnormal findings and the issues and choices that would have to be made place amniocentesis in a unique position. Deciding whether to have an amniocentesis is one of the most difficult decisions some women must make during pregnancy. Some women can make this choice easily, while for others it is very difficult. There is no right choice. Whatever the woman's decision is, it must be supported. She and her family have to live with the decision and outcome.

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