Objective
Our objective was to determine the impact of disclosure of echogenic intracardiac focus (EIF) on the rate of amniocentesis in women who have undergone sequential testing.
Study Design
This was a retrospective study of women who had sequential testing for Down syndrome from 2009 through 2011. The Down syndrome risk was doubled in pregnancies with EIF, consistent with counseling provided to patients. In the control group Down syndrome risk was based on sequential testing. Within risk categories (1 in <250, 251-1000, 1001-5000, >5000) rates of amniocentesis with and without documented EIF were compared using Fisher exact test.
Results
In all, 4429 women at a median maternal age were included, including 229 with EIF (5.2%). In those at highest Down syndrome risk (1 in <250), rates of amniocentesis were similar between the 2 groups. In those at lower levels of risk, the rate of amniocentesis was significantly higher following disclosure of EIF compared to pregnancies without EIF at similar levels of risk.
Conclusion
Except for those at highest risk, rates of invasive testing were significantly higher in pregnancies with isolated EIF vs those at comparable risk.
Second-trimester sonographic findings associated with Down syndrome can be used to adjust Down syndrome risk in individual patients. While this can provide accurate risk assessment, many women having second-trimester ultrasound have undergone risk assessment with nuchal translucency and biochemistry. Those who have declined invasive testing are likely to have very low a priori risk. In these patients, adjusted risk will remain low even in the presence of a sonographic marker of Down syndrome.
The most prevalent ultrasound finding associated with Down syndrome is the echogenic intracardiac focus (EIF). EIFs are thought to represent calcifications of the papillary muscle. They are commonly seen in the left ventricle, with a reported prevalence of up to 5%. Unlike other markers, such as pyelectasis or echogenic bowel, which may reflect other structural or genetic abnormalities, there is no known clinical significance to EIFs other than an increased Down syndrome risk. EIFs in isolation are associated with an increased risk of Down syndrome, with likelihood ratios (LRs) generally ranging from 1.5–5.0 in published studies. Our objective was to determine the impact of identifying EIFs on the rate of amniocentesis in women who have undergone first- and second-trimester risk assessment for Down syndrome.
Materials and Methods
This was a retrospective study of women with singleton pregnancies who had sequential testing for Down syndrome from 2009 through 2011 and subsequently underwent second-trimester ultrasound in our department. In sequential testing, Down syndrome risk was calculated based on maternal age adjusted by nuchal translucency and pregnancy-associated plasma protein A at 11-14 weeks, and free-β-human chorionic gonadotropin, estriol, alpha-fetoprotein, and inhibin-A at 15-20 weeks.
After sequential testing, all women are given the option of amniocentesis, regardless of maternal age or level of risk. After ultrasound findings associated with chromosomal abnormalities are identified, women who have not undergone invasive testing are counseled about the findings, and risk is adjusted by applying relevant LRs. Women are again informed about the option of amniocentesis.
In pregnancies with isolated EIF, the risk of Down syndrome used clinically and for this study was doubled from the sequential testing risk by applying LR for isolated EIF of 2.0. This LR was consistently applied throughout the study period. Patients were informed about the finding and adjusted risk by maternal-fetal medicine physicians at the time of ultrasound and were counseled about the option of amniocentesis including a procedure-related pregnancy loss rate of <1 in 300-500. In pregnancies without EIF, the risk used in this study was based on sequential testing, as the absence of any ultrasound findings was not used to reduce risk in patients who had decided to forego amniocentesis after sequential testing.
We compared the rate of amniocentesis in pregnancies with and without EIF. Risk was stratified into 4 categories: 1 in <250, 1 in 251-1000, 1 in 1001-5000, and 1 in >5000. Pregnancies with additional sonographic markers of Down syndrome or major structural abnormalities were excluded. Pregnancies in which the main indication for amniocentesis was for reasons other than assessing fetal karyotype were excluded. Fisher exact test, Mann-Whitney U , and logistic regression were used for statistical analysis. Institutional review board approval was obtained to review medical records.
Results
There were 4429 women at a median maternal age of 33 years (interquartile range, 31–36) who were included. EIF was identified in 229 pregnancies (5.2%), and median maternal age was less in these pregnancies than in pregnancies without EIF, 32 years (interquartile range, 30–34) vs 33 years (interquartile range, 31–36) ( P = .002). EIF was significantly more common in those of Asian descent compared to non-Asians (7.1% vs 4.9%; P = .04). In the entire group, median Down syndrome risk based on sequential testing was 1 in 14,794 (interquartile range, 3893–58,412), and those with EIF had higher median risk compared to the remaining pregnancies, 1 in 6091 (interquartile range, 2158–10,112) vs 1 in 15,831 (interquartile range, 4070–61,810) ( P < .001). In pregnancies with EIF, risk based on sequential testing was <1 in 1000 in 83.4% of cases, and <1 in 5000 in 55.5%.
The overall rate of amniocentesis was 5.5%. The rate of amniocentesis was strongly correlated with adjusted risk, and ranged from 49.3% in the highest-risk category of 1 in <250, to 2.5% in the lowest-risk category of 1 in >5000.
The rate of amniocentesis was significantly higher in pregnancies with EIF (19.7% vs 4.7%; P < .001) compared to those without EIF. In those at highest Down syndrome risk (1 in <250), rates of amniocentesis were similar between the 2 groups. In those at lower levels of risk, however, the rate of amniocentesis was significantly higher following disclosure of EIF compared to pregnancies without EIF at similar levels of risk ( Table 1 ). Logistic regression was used to adjust for age in each risk category. The presence of EIF was found to be independently associated with amniocentesis in the 3 lower risk categories ( Table 2 ).
| Down syndrome risk | Amniocentesis rate (overall) | EIF | No EIF | P value a |
|---|---|---|---|---|
| 1 in <250 | 72/146 (49.3%) | 12/24 (50%) | 60/122 (49.2%) | 1.0 |
| 1 in 251-1000 | 41/279 (14.7%) | 11/30 (36.7%) | 30/249 (12.0%) | .001 |
| 1 in 1001-5000 | 53/968 (5.5%) | 17/121 (14.0%) | 36/847 (4.3%) | < .001 |
| 1 in >5000 | 76/3036 (2.5%) | 5/54 (9.3%) | 71/2982 (2.4%) | .01 |
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