Thoughts about Prenatal Screening Tests

[Jayla]

it seems that prenatal screening (triple screen, ultrasound) often cause unecessary anxiety in expecting parents. what are some experiences and thoughts regarding this issue?

obstetrical sonography:

the best way to terrify a pregnant woman

roy a. filly, m.d.

i have just reached the 30th anniversary of the first obstetrical sonogram i performed. even having witnessed each of the technological advancements in sonography over those three decades, it is still difficult to comprehend the enormous improvements in image quality that have occurred. these improvements have brought sonography from a "promising" diagnostic tool to a mainstay of modern imaging. however, nowhere in medicine has this technique had a more profound impact than in the field of obstetrics. thirty years ago there was essentially no such thing as obstetrical imaging and prenatal diagnosis was in its infancy.

during this time obstetrical sonography went from a medical oddity to a test of such great value that several european countries perform at least two obstetrical sonograms in every pregnant woman and 70% of modern american mothers have had a sonogram during their pregnancy (1,2). obstetrical sonograms provide a wealth of useful information to the primary care giver. some of these benefits are easily measured: accuracy of estimating menstrual age, accuracy of predicting twins, etc. others are more difficult to measure but we all agree are nonetheless of great benefit. one of the most important of these is providing "reassurance" to the expectant mother. in our obstetrical department the phrase "for size and dates and general reassurance" seems to be pasted on nearly all sonogram request forms. personally, the opportunity to say, "everything looks fine" to an expectant mother was one of the perks of my job. i can see the wave of relief wash across her face. it's always a touching moment followed by "thank you, doctor".

today, i no longer feel that way. there are a growing number of patients where i dread having to speak to her. i have reviewed the sonographer's scans and they disclose a finding that will send the mother into a tailspin of confusion and worry. i'm not talking about holoprosencephaly or bilateral renal agenesis. i have a great deal of experience discussing such devastating diagnoses with pregnant women. and while the news is sad, i always feel that i am providing the family with a great service. nothing can change the fact that her fetus has a mortal anomaly. there will necessarily be a grieving period and tears will undoubtedly flow, but beginning that grieving period at the earliest possible date in her pregnancy is "good medicine".

tomorrow when i return to work the odds are i will have to speak to a mother-to-be about an "abnormality" that i see on her sonogram and i won't know what to tell her. i am talking about "abnormal" findings on her sonogram which loosely fit under the general heading of "down syndrome markers" (some are actually better as markers of other trisomy syndromes). i am not referring to atrio-ventricular canal or duodenal atresia. these are strong indicators that the down syndrome may be present. but down syndrome or not, the fetus still has a serious anomaly and the detection of that anomaly is a benefit. what i am afraid to encounter tomorrow is an "abnormality" which is not really abnormal: choroid plexus cysts (3-31), echogenic intracardiac foci (32-36), mild pyelectasis (37-41), and echogenic bowel (42-45) . if her fetus has one of these "abnormalities" but doesn't have the down syndrome, then her fetus is normal. excuse me, i'm certain i will be criticized if i don't tell the mother-to-be that in the absence of the down syndrome and the presence of echogenic bowel she must worry about her fetus having cystic fibrosis, developing intrauterine growth restriction, having a premature birth, a fetus with a cytomegalovirus infection, or a fetus who may die in her womb (46-49). alternatively, if her fetus has mild pyelectasis and a normal karyotype her newborn child is at risk for urinary tract problems, must take antibiotics after birth, get an extensive and uncomfortable work-up for vesico-ureteral reflux and must be followed-up for many months to ensure normalcy (50).

the sheer numbers of papers written on the subject only add credibility to their importance (3-49). certainly, some authors disagree as to the importance of one or the other of these findings (51,52). unfortunately, the physician performing a routine sonogram and finding one of these "markers" is hard pressed to make a determination regarding which expert to believe. inevitably they choose the "safest" path; at least, "safest" from a medico-legal perspective. the mother is simply going to have to deal with the possibility that her fetus may have the down syndrome or worse.

these down syndrome markers are common findings in normal fetuses, particularly the echogenic intracardiac focus (eif). eif occurs in approximately 5% (it is probably closer to 10%) of fetuses (53). the choroid plexus cyst occurs in 1-2% of fetuses (3), echogenic bowel occurs in approximately 1% of all second-trimester fetuses (44) (many more if high frequency transducers are employed) and mild pyelectasis in 3% of normal fetuses (54). if you have a busy sonographic practice seeing 10-20 pregnant woman daily, you will most likely see one or the other of these "abnormalities" every day.

the researchers that originally described these findings did so in women at high risk to have a fetus with the down syndrome (55-65). these were pregnant women older than 35 years or who had a positive "triple marker" screening test for the down syndrome. in this group of women the application of these findings increases the probability of finding down syndrome fetuses and they perform admirably in this regard. however, these women have already been counseled that amniocentesis is appropriate in their case. they are having a sonogram in order to downgrade their risk to a level where they may appropriately forego amniocentesis (66-76). when examining a mother-to-be in this circumstance i fully recognize the value of identifying these "abnormalities" and can counsel these women appropriately that their already substantial risk is further increased if i find one or more of these features. more importantly to her, if no markers for the down syndrome are found her level of risk may be significantly reduced (67, 72, 73).

but then investigators (with the best of intentions, i am certain) appear to have taken a misstep. these findings when seen in a woman with a low risk of having a down syndrome fetus were used to upgrade her risk (40, 77). the consumers of this information, the physicians in the trenches, read these scientific papers and then identify these "abnormalities" during a routine sonogram. what are they to tell the patient? this woman hasn't already been counseled. she is having a sonogram for "reassurance" (forget that now). her husband, children and parents are with her. there is a party atmosphere. the videotape is rolling. soon the giggling and finger pointing at the screen will cease. the questions will change abruptly from "is that the heartbeat?" or "is that the member there?" to "are you saying that my child is going to be mentally retarded?"

without doubt you have now added cost to the management of that pregnancy. the patient may choose to undergo amniocentesis. she may be referred to a prenatal diagnostic center for a detailed fetal sonogram and genetic counseling. the innumerable hours of counseling by primary care givers and general sonologists to explain the "meaning" of this finding are not counted in these additional costs (78). nor are the heartaches of the parents-to-be counted in this cost analysis. if they forego the amniocentesis (clearly the correct choice, in my opinion) then they must live with residual doubt for the remainder of the pregnancy. does my fetus have the down syndrome? maybe i should have had the amniocentesis. the enjoyment of the anticipation of the birth of their son or daughter is now replaced with anxiety.

well you say, look at all the good these findings have accomplished. some bad must go along with all that good. possibly i am the exception (i doubt it), but i don't see "all the good". i am a simple-minded physician. i like it when a sonographic finding passes the "thank god test". the thank god test is passed when i say to myself "thank god" for that finding. if i hadn't seen it i would have completely missed this devastating abnormality. i have no instance in my recollection where one or the other of these abnormalities was the sole reason i was able to recognize a fetus with the down syndrome in a low risk patient. (this presumes, of course, that a reasonably careful sonogram following the aium guidelines has been performed.) obviously someone has had such an experience: just not me. from my vantage point the identification of these "abnormalities" in low risk women has crossed the line of "more harm than good".

what are we trying to accomplish with the sonographic observation of "down syndrome markers" in low risk women? twenty percent of down syndrome fetuses are born to mothers 35 years or older. we have known for many years that we must be suspicious in this group. maternal serum screening programs for the so-called "triple markers" in women

so then, what should i do tomorrow? should i have the courage of my convictions and simply ignore these features? i wish i had that courage, but i don't. even with my considerable "clout" in the world of obstetrical sonography, i cannot unilaterally ignore the sonographic medical literature. that is not how american medicine works.

i am confident that i am not alone in my concerns regarding this issue. i further believe that the authors who did this excellent research in the "high risk" population are becoming aware that these features are not proving as beneficial in the "low risk" population as they had hoped. it is time for the american institute of ultrasound in medicine or the american college of obstetrics and gynecology to convene a panel of experts to analyze the data on this issue and publish a position paper on the practicality of employing down syndrome "markers" in low risk women at the soonest possible date.

[fergus51]

After having worked NICU for a while I believe that parents have every right to these tests, and they are a particularly good idea for high risk women. Parents who are prepared have a much easier time than parents who get shocked with a surprise diagnosis. Plus, on the practical side it helps to know where they should deliver.

[SmilingBluEyes]

I think ANY parent, when considering such tests had best ask him/herself this question:

"what will I do with the results of such tests?" (whether they turn out favorably or not)

I have always advised my family members the same way....consider risks versus benefits. Example, I became pregnant after 35 (having had a previous baby with a birth defect). They offered me amnio at about 17 weeks. I deferred---over what I daresay was a strong protest by the geneticist to whom I was referred for counseling. It was not worth it to me----I did not want to risk miscarriage---and believe it or not, that risk was greater than my chance of having a Down's -affected baby (or another child with my son's birth defect).

It was not that I may not have wanted to know about chromosomal problems-----but it would not have changed my outcome in my case. I would NEVER have aborted the baby and I would have taken what I had gotten and dealt with it step by step, as I had with my son. My dh and I had agreed ahead of time to refuse amniocentesis. So there is an example of opting-out when one knows such testing would not benefit her or her baby.

There are others who would WANT to know, for what I would think are obvious and valid reasons. Perhaps to be prepared for special-needs child. Perhaps, as in my case, there was a previous birth defect in another child. Perhaps to be able to change the outcome of the pregnancy---esp if the problem is incompatible with any extrauterine life. To be sure, it's a very emotional and private issue for families to face ---- Each must decide what is best for his/her family situation.

Anyhow, I believe: If one can answer that question honestly and clearly, then he/she will know best how to proceed. He or she may not choose to take risks by submitting to various prenatal testing----or maybe they will. But it should be the parent's choice always to opt out or go forward with any prenatal testing offered, after being educated as to how such tests can be beneficial/and the risks that may be involved.

[Jayla]

very interesting points. i guess what concerns me with certain screening tests are the high rates of false positives causing unecessary stress. what i though was interesting about this article was the idea that in any office doing high numbers of sonograms on low risk women, chances are they will be discussing the "possibility" of abnormal results with at least one woman per day.

[color=#4b0082]if you have a busy sonographic practice seeing 10-20 pregnant woman daily, you will most likely see one or the other of these "abnormalities" every day.

in addition, this is more of a concern for the uninsured woman paying out-of-pocket for procedures like a f/u amnio.

[SmilingBluEyes]

There were no obvious abnormalities at all with my son in 3 separate OB u/s scans........yet was born with synostosis of the skull. (for which he later had to have craniotomy)

There were definite "short femur" measurements w/my daughter (can be linked to Down's Syndrome in some cases). She was born free of any problems whatsoever.

go figure....you are right, no test is 100%.......so....

Like I said, you better know what you plan to do with the results of any testing before you go in----or you can always defer. Lord forbid ANYONE take personal responsibility for her own prenatal care, hummm? We always have the option to ask, ask and ask more questions, or read up. There is more info available than ever now. (certainly more than even when my son was born).

Anyhow, good points, Jayla.

[Jolie, BSN]

SBE stated very well the importance of risk vs benefits in deciding which prenatal tests to persue, although I must admit that I've never considered an U/S to be one of the tests that I would potentially decline due to the high incidence of false positives. Triple screens have long been problemmatic for this reason, and amnios are concerning due to the potential risk of losing the pregnancy, but I have always considered U/S to be pretty innocuous. I guess this may change my way of thinking.

[Spidey's mom, ADN, BSN, RN]

Weighing in here as a so-called high risk mom, having had a baby at 44. Actually I'm taking care of a mom today, G8P7 who is 44.

My OB ended up scaring the heck out of me, all for nothing. My AFP came back indicating I was carrying a Down's Syndrome baby - not being very familiar with this test, I did some research (after a diagnostic ultrasound and amnio) and found that the ONLY reason was my "advanced" age - NO blood markers at all were found for Down's.

Having been through that experience, I have to say that I agree with the doc in the article that you have a real quandry with low-risk families . . . .

There are so many reasons for the so-called "false positives" that turn out to be nothing. I have to agree that technology may be giving us too much information based on fear only.

We wouldn't have aborted even if the amnio came back positive for birth defects . . . so why did I have one? I think the combo of the surprise of being pregnant in my 40's and the fear my OB instilled in me as a "high risk" pregnancy overcame my logic. It is an emotional time when you are pregnant . ... . .making decisions like this are difficult. I'm grateful nothing bad happened after the amnio - but I would not do it again. Calmer mind now of course.

Good article -lots to think about.

steph

[wannabeL&D73]

As stated above, I think that the pts. need to be very clear about what they would do with the results. Many pts. are not given truly informed consent, for example they are given the AFP without even knowing what is being screened for. Also, I think that women should be aware that in many places, if the test results are abnormal, they will be placed under an extreme amount of pressure to terminate. For example with a diagnosis of Down syndrome, a great number of drs. are giving inaccurate, out-of-date information on the reality of raising a child with Ds. Often the appt. has been made to terminate even prior to the test results being discussed. The new screening test which is non-invasive and done in the first trimester is predicted to result in an approximate 80% reduction in the number of babies born with Ds.

For many people a pre-natal diagnosis allows them to go through the grieving process prior to birth, so that when the baby is born they are able to fully celebrate and embrace the baby. Personally, I was glad not to have known that my son had Trisomy 21 (we refused testing) and he is now the light of our lives (along with his sister), and just started walking in time for his 2nd birthday!

Shannon