Fruit of the Womb
Fruit of the Womb

Amniocentesis Q & A

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Yesterday, I addressed the issue of ‘risk’ related to amniocentesis. I thought I should clarify that there are many different reasons we do an amniocentesis, and there are many different times during a pregnancy when it might be indicated that this be done. 'Risk' varies somewhat by time in the pregnancy and indication, and the outcome of a ‘complication’ can be quite different, depending on the gestational age. In the post yesterday, I was specifically addressing the issue of a ‘genetic amniocentesis’, most commonly done between 15 and 22 weeks to determine the fetal karyotype (chromosomes) and to look for evidence of a known or suspected genetic abnormality (inborn error of metabolism). The ‘risk’ addressed in the FASTER trial cited in the post from yesterday is only the risk of losing a baby (prior to viability) after a genetic amniocentesis has been done in midtrimester.

Whenever a woman is considering a genetic amniocentesis during pregnancy, usually one or more of the questions below are among those on her mind. Although the answer to these will vary by provider, let me give you my typical responses:

· “Do you have to stick the baby?” – No, we try to avoid that by looking with the ultrasound while we are doing the procedure. We are actually going to take some of the fluid (about 2/3 oz) from around the baby. The fluid is mostly fetal urine (“baby pee”) at this point in the pregnancy and it contains cells from the baby that we can then grow in the laboratory to determine the baby’s chromosomes. After we get done, the fluid around the baby will look no different to you and the baby will quickly replace the small amount we have removed.

· “Does it hurt? (usually phrased as “My friend told me this REALLY hurts!?!”)” - Usually it is SO painful that we have to have several large nurses sit on you while I do the procedure! No, seriously, we use a very thin needle, thinner than the one they use to draw blood or start an IV. You will probably not feel it much at all as I go through the skin and you will probably feel a cramp, like a menstrual cramp, when I go into the uterus. I will warn you when I am going to do that. You can have someone hold your hand while I am doing the procedure if you would like. Most folks say when it's over that "it wasn't as bad as I thought it was going to be."

· “Are you going to numb me up?” – I can if you would like, although I usually do not and hardly ever have since we started using these thin needles about 20 years ago. The numbing medicine usually hurts more than the needle stick and I can’t numb the uterus to stop the cramp I told you about. Also, if the baby moves, then I might have to stick you 3 or 4 times rather than just once.

· “What are the risks of the procedure? (usually phrased as “My baby moves a lot, what will happen if he/she gets stuck with the needle?”)” – The risk of losing the baby as a result of the procedure is less than 1 in 1000. Other risks include the possibility of breaking the bag of waters, that may or may not lead to delivery or other complications (which I usually do not discuss unless the patients asks at this point), the risk of introducing infection into the uterus, although this is so rare that we do not use any antibiotics to do this procedure and, to help prevent that, we clean your abdomen off first with an antiseptic solution (cold, wet, and scratchy, runs all over the place - the worst part of the procedure) and use sterile drapes (so please do not try to help me with this procedure), and the risk of bleeding either from the placenta if we have to insert the needle through that to get to the fluid, or from the baby, either because of hitting a fetal-placental blood vessel or the baby’s umbilical cord. Again, we try to avoid the latter events by watching with the ultrasound while we do the procedure; even if we do get some bleeding, which is not uncommon when we go across the placenta, it usually stops very quickly and we will watch it until it does. If you are Rh-negative, we will give you Rh-immune globulin after the procedure to help prevent ‘sensitization’ unless you know the baby’s father is Rh-negative too. (I usually do not discuss the possibility of isoimmunization in general unless the mother is Rh-negative or there is substantial bleeding afterwards). I will also be trying to avoid hitting the baby and plan, intentionally, to place the needle away from the baby’s head, but if the baby does move and hit the needle, I will tell you what part of the baby got hit so that we can follow up after the baby is born. Usually there are no long term consequences of this.

· “If I do this test, will it tell me that I am going to have a normal baby?” – That is not an easy question to answer. Chances are, if the chromosomal studies are normal, and we don’t see any abnormalities of the baby, the odds are in your favor the baby will be ‘normal.’ There are rare circumstances when the baby will have a chromosomal problem that is not picked up by the studies or a genetic problem that we did not know about so that we could look, specifically, for it. Other things can also happen during the pregnancy, unrelated to the amniocentesis that could cause the baby not to be ‘normal’ as well.

· “How long does it take to do? (usually phrased as “How long is that needle going to be in me!?!”)” – It usually takes me longer to clean and drape your abdomen than it does for me to do the procedure. Once the needle is in the uterus, it takes about 30 seconds to draw off the fluid because the needle is so thin.

· “How long before I get the results back (usually phrased as “You mean I am NOT going to find out today if my baby’s alright!?!”)” – If we see nothing wrong with the baby, or if you do not have a risk for a specific chromosomal abnormality, such as Down syndrome or trisomy 18 based on other studies, it usually takes 10 to 14 days to get the final results. We can do a rapid screen called FISH (fluorescent in situ hybridization) for a limited number of specific chromosomal abnormalities if one of these is suspected. The results of FISH are usually back within 72 hours, but it does not screen for all chromosomal abnormalities, so routine cultures are also done and you will still have to wait 10-14 days to be completely reassured. The FISH test is also expensive and may not be covered by your insurance carrier because they look at it as a ‘preliminary test’ result.

· “How many days will I have to stay at bed rest? (usually phrased as “Can you give me a note for work for the next week?”)” – Unless there is a complication of the procedure, you will not have to go home to bed rest. We do recommend that you avoid heavy lifting and other exertional activities today and drink some extra fluids. If you think today will be a problem at work, we will give you a note.

· “What do I look for to suggest a problem” – Leakage of fluid, cramping, pain, bleeding, fever – It is not unusual to have a little cramping over the first 24-48 hours after the procedure and you can take Tylenol, or even a few doses of over-the-counter strength ibuprofen, for this, but if it continues longer than that, or if you develop any of the other problems, you need to let your doctor know.

· “When can we have sex again? (usually this one comes from the partner, and the woman is usually grateful when I jokingly answer “NEVER”)” – I usually recommend that you avoid intercourse for 48-72 hours – wait at least 24 hours after the cramping has gone away.

· “How will I get the results” – We will call you as soon as they come back from the laboratory. Do you want to know for sure if the baby is a boy or a girl?

After we have finished the procedure, I usually ask if there are any more questions, wish them the best on the outcome, and tell them that, hopefully, they won’t need to come back to see me again during the pregnancy!
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About the Author

Dr. Trofatter is an expert on maternal-fetal medicine.

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