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ABSTRACT

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Objective

First-trimester aneuploidy screening has high detection rates and low false-positive rates. Their use as well as the implementation of non-invasive prenatal testing may affect specialty training in prenatal diagnosis procedures.

Study design

Descriptive study of first-trimester aneuploidy screening and amniocentesis in an obstetric training program. Screening methods were tracked from their introduction in 2004 through 2011. The volume of amniocentesis procedures from 2000 to 2011 was evaluated.

Results

First-trimester screening tests increased from 283 to 1225 between 2005 and 2011, whereas genetic amniocenteses declined from 460 to 168 during the same period. The percent of older women who chose a first-trimester screen test rose from 12.7% to 44.2%

Conclusion

First-trimester screening options reduce genetic amniocenteses available for training. Fetal medicine and general obstetrics training programs need to evaluate their clinical experience and determine whether simulation training methods are needed for education. © 2013 John Wiley & Sons, Ltd.


INTRODUCTION

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

First-trimester screening options for the detection of fetal aneuploidy are well established in the United States. Tests using first and second-trimester serum analyte markers combined with nuchal translucency measurement are superior to second-trimester quad screening with detection rates up to 90% and false positive rates as low as 1–2% in the second trimester of pregnancy.[1, 2] These improvements in non-invasive screening have led to decreases in the number of screen-positive results and, therefore, in the number of women offered amniocentesis for detection of chromosomal aneuploidy.

Recently, the use of non-invasive prenatal testing has been validated for the detection of the most common aneuploidy syndromes in high-risk women.[3-6] Now, with the potential integration of non-invasive prenatal testing into the screening algorithm, the number of patients offered prenatal diagnosis procedures is likely to decrease even further.

A significant decline in prenatal diagnosis procedures has significant implications for the training in obstetrics. This report describes how the implementation of first-trimester screening options has affected amniocentesis rates in a population where integrated screening is the preferred screening test for women of all ages.

METHODS

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

This is a descriptive study of the implementation of first-trimester screening options and invasive genetic testing from the three tertiary care training centers where University of Utah trainees have access to invasive procedures. Data from 2000 to 2011 were evaluated, which includes the time prior to implementation of first-trimester screening options in our system in 2004. All genetic amniocenteses, chorionic villus sampling procedures, and screening tests utilizing nuchal translucency measurements with first-trimester serum analytes were evaluated. Second-trimester maternal serum triple-screening and quadruple-screening tests were not included in the analysis.

Screening data were obtained from the regional laboratory that is responsible for all of the genetic screening and testing in our health systems. Patients at these three sites would be unlikely to have screening performed elsewhere because patients must see a genetic counselor for either screening or invasive procedures; genetic counselors are only available at these sites for these two health systems. To quantitate the number of procedures available for training, all procedures are reported, regardless of whether they were performed by trainees. Descriptive statistics were calculated, and the data were plotted for ease of analysis. Data regarding women 35 years and older were also evaluated separately, to demonstrate this group's acceptance rate of screening.

The study was approved by the institutional review boards of the University of Utah School of Medicine and Intermountain Healthcare. Both institutions considered them exempt from institutional review board reporting because of the de-identified data analyzed; therefore, it was not reviewed by an ethics committee.

RESULTS

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Following their introduction in our healthcare systems in the fall of 2004, utilization of non-invasive early screening methods increased from 283 patients in 2005 to 1225 patients in 2011. Over the same period, the annual number of genetic amniocentesis procedures declined from 460 to 168 (Figure 1).

image

Figure 1. First-trimester screening and amniocentesis rates: 2000–2011

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The decline in the number of amniocenteses is not completely explained by a shift to other invasive diagnostic procedures. Although the number of chorionic villus sampling procedures increased by 40.6% between 2004 and 2011, the absolute increase during that time was only 24 procedures per year (Figure 1). Also, the decreased number of amniocenteses is not explained by a smaller population base. Between 2004 and 2011, the combined number of deliveries in our three tertiary centers increased by 46%, from 7708 to 10867.

After introduction of first-trimester testing options, the percentage of screening patients who were aged 35 years or older increased from 12.7% to 44.2%, indicating that more older women chose non-invasive screening in a cohort traditionally considered to be at increased risk because of advanced maternal age (Figure 2).

image

Figure 2. Advanced maternal age and rates of first-trimester screening options: 2000–2011

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Review of the number of amniocentesis procedures performed in the 4 years prior to introduction of early genetic screening found that a decline in utilization was already underway. Between 2000 and 2003, the number of amniocenteses performed in our system dropped by 15.6%, from 749 in 2000 to 632 in 2003 (Figure 1). Dividing the time period 2000–2011 into three four-year epochs, we found that the decline in genetic amniocentesis procedures is striking, decreasing from an average of 673 per year in 2000–2003 to an average of 270 per year in 2008–2011 (Figure 3).

image

Figure 3. Average annual volume of genetic amniocenteses: 2000–2011

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DISCUSSION

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

In 1994, Haddow et al.[7] measured the serum markers alpha fetoprotein, human chorionic gonadotropin, and unconjugated estriol in 5385 women prior to amniocentesis for advanced maternal age. The study estimated the theoretical decrease in procedures that could be achieved with the use of second-trimester triple analyte screening. Using a screening cutoff of 1:200 for fetal Down syndrome, they calculated that about 75% of the procedures could be avoided because of a negative triple screen result.

Integrated screening techniques have dramatically improved the detection and false positive rates for the most common trisomies. As a result, the utilization of early screening for aneuploidy has substantially increased in our population since its introduction, including the group of women 35 years and older. This has contributed to a 65.1% decrease in genetic amniocentesis procedures being performed in our centers since 2004. This decline is likely to continue as non-invasive prenatal testing in maternal blood becomes more available and accepted. Although microarray analysis adds more genetic information than conventional karyotype for prenatal diagnosis and may increase prenatal diagnostic procedures,[8] the application of microarray analysis through non-invasive prenatal testing is likely to continue the trend to accessing the fetal genome through non-invasive means.

Currently, as invasive testing for aneuploidy has decreased, other methods of fetal assessment and treatment have replaced amniocentesis for non-genetic indications. Measurement of blood velocity in the middle cerebral artery has replaced serial amniocenteses with amniotic fluid bilirubin measurement for assessment of the fetus at risk for anemia. In the treatment of twin–twin transfusion syndrome, serial reduction amniocentesis has largely been replaced by endoscopic laser therapy. Finally, restriction of elective labor inductions before 39 weeks may have led to fewer amniocenteses being performed for pulmonary maturity testing prior to delivery.[9] All of these factors mean that there are fewer second and third-trimester amniocentesis procedures available for training obstetrics and gynecology residents, and advanced fetal medicine trainees.

Although the loss rate from invasive procedures is difficult to accurately determine, amniocentesis has become a safer procedure over the last 40 years, as ultrasound has improved and smaller needle diameters have been adopted. In the early 1980s, when 20-gauge needles were commonly used and ultrasound guidance was not as refined as today, procedure-associated loss rates of around 1% were reported.[10] More recently, Odibo et al. reported on their single-institution, 16-year experience with amniocentesis. Their overall fetal loss rate was 0.13%, or 1 for every 769 procedures.[11] Most recently, no increase in the pregnancy loss rate was seen in women who underwent an amniocentesis as part of the FASTER trial of integrated screening, compared with those who did not.[12]

As the number of patient procedures available for direct training declines, the use of simulation models may be essential for developing technical competence. In 1998, Smith et al. reported the first amniocentesis simulation model, noting that program requirements for residents included training in genetic amniocentesis.[13] They described a model in which a gelatin mold is made with a submurged balloon filled with opaque liquid to simulate an amnion. Zubair et al. described an amniocentesis simulator using a formalin-preserved gravid pig placed in a plastic bag of ultrasound gel.[14] Other programs have also reported simulation training.[15] Today, several reusable amniocentesis simulation models are available on the commercial market.

Our experience indicates that amniocentesis procedures available for postgraduate training are decreasing. Performing fewer procedures can affect the competence of trainees and therefore may affect unfavorably the complication rate. For prenatal diagnosis to continue to be a safe and effective procedure, obstetric education programs will need regularly to evaluate the number of amniocentesis procedures that are available for training and to determine how many individuals can be adequately trained in the technique. To make up for the shortfall in patient procedures, training programs will also need to consider the routine addition of simulation models as part of their education programs.

It may be prudent to consider standardization of a model to validate competence for amniocentesis procedures. Also, if our data are borne out on a national level, the diminished need for amniocentesis suggests that fewer providers will be needed in the future, and training could be limited to a smaller number of trainees.

Finally, obstetric educational programs should evaluate its curriculum to be certain that physicians are trained and skilled in counseling for early aneuploidy screening and that adequate training and experience with prenatal counseling, screening, and diagnostic procedures are available

WHAT'S ALREADY KNOWN ABOUT THIS TOPIC?

  • It is known that increasing efficiency with all forms of screening decreases the need for definitive prenatal diagnosis procedures. As non-invasive prenatal testing improves and has increased utilization, it is likely that the volume of prenatal diagnosis procedures will continue to decrease.

WHAT DOES THIS STUDY ADD?

  • Because we have essentially 100% ascertainment of all samples in our region, we can actually define how few amniocenteses are available for obstetric training and experience. This manuscript attempts to demonstrate with data the decline in procedures to perhaps begin a dialog on changing how we train fellows for procedures.

REFERENCES

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES
  • 1
    Malone FD, Canick JA, Ball RH, et al. First-trimester or second-trimester screening, or both, for Down's syndrome. N Engl J Med 2005;353:200111.
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    Wald NJ, Watt HC, Hackshaw AK. Integrated screening for Down's syndrome on the basis of tests performed during the first and second trimesters. N Engl J Med 1999;341:4617.
  • 3
    Palomaki GE, Kloza EM Lambert-Messerlian GM, et al. DNA sequencing of maternal plasma to detect Down syndrome: an international clinical validation study. Genet Med 2011:91320.
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    Enrich M, Decia C, Zwiefelhofer T, et al. Non invasive detection of fetal trisomy 21 by sequencing of DNA in maternal blood: a study in a clinical setting. Am J Obstet Gynecol 2011;204:205.e111.
  • 5
    Bianchi DW, Platt LD, Goldberg JD, et al. Genome-wide fetal aneuploidy detection by maternal plasma DNA sequencing. Obstet Gynecol 2012;119:890901.
  • 6
    Norton ME, Brar H, Weiss J, et al. Non-invasive Chromosomal Evaluation (NICE) Study: results of a multicenter prospective cohort study for detection of fetal trisomy 21 and trisomy 18. Am J Obstet Gynecol 2012;207(2):137.e1–8.
  • 7
    Haddow JE, Palomaki GE, Knight GJ, et al. Reducing the need for amniocentesis in women 35 years of age or older with serum markers for screening. NEJM 1994;330:11148.
  • 8
    Wapner RJ, Martin CL, Levy B, et al. Chromosomal microarray versus karyotyping for prenatal diagnosis. NEJM 2012;367:217584.
  • 9
    American Congress of Obstetricians and Gynecologists. ACOG Practice Bulletin #107: induction of labor. Obstet Gynecol 2009;114:38697.
  • 10
    Tabor A, Philip J, Madsen M, et al. Randomised controlled trial of genetic amniocentesis in 4606 low-risk women. Lancet 1986;1(8493):1287.
  • 11
    Odibo AO, Gray DL, Dicke JM, et al. Revisiting the fetal loss rate after genetic amniocentesis. Obstet Gynecol 2008;111:58995.
  • 12
    Eddleman KA, Malone FD, Sullivan L, et al. Pregnancy loss rates after amniocentesis. Obstet Gynecol 2006;108:106772.
  • 13
    Smith JF, Bergmann M, Gildersleeve R, Alle R. A simple model for learning sterotactic skills in ultrasound-guided amniocentesis. Obstet Gynecol 1998;92:3035.
  • 14
    Zubair I, Marcotte MP, Weinstein L, Brost B. A novel amniocentesis model for learning stereotactic skills. Am J Obstet Gynecol 2006;194:8468.
  • 15
    Pittini R, Oepkess d, Macrury K, Reznick R, Beyene J, Windrim R. Teaching invasive perinatal procedures: assessment of a high fidelity simulator based curriculum. Ult Obstet Gynecol 2002;19:47883.
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