Trisomy 18 (Edwards Syndrome)
Alaska, 2007-2021
Background
Edwards syndrome, or Trisomy 18, is a condition in which an infant is born with an extra chromosome. Chromosomes are small packages of genetic material responsible for inherited traits. They determine how an infant’s body forms and grows during pregnancy and how it will function after birth. Typically, an infant has 23 pairs of chromosomes, half from each parent. An infant with Edwards syndrome has an extra copy of chromosome 18, which is why this condition is often referred to as Trisomy 18 (i.e. three copies of chromosome 18).[1] This extra copy of chromosome 18 changes how the infant’s body and brain develops, causing delayed fetal growth, low birth weight, and problems with cognitive development. Edwards syndrome often results in abnormalities of vital organs, including the heart and lungs. Physical features of the condition may include a small, head, a small mouth and jaw, and misshapen hands. Due to the severity of these medical problems only 5-10% of babies with this condition live past their first year of life and those that do have severe intellectual and physical disability.[2] The majority of Edwards syndrome cases are often identified in the first trimester of pregnancy by prenatal screening.[3]
Most cases of Edwards syndrome are “spontaneous”; they occur when the mother’s eggs or father’s sperm cells are developing for no obvious reason. Studies suggest that there is an underlying genetic component that causes Edwards syndrome, and mothers who are over 35 may be more likely to have a child with Edwards syndrome.[4]
Epidemiology
Alaska Birth Defects Registry (ABDR) registers birth defects as reported from health care providers using International Classification of Disease (ICD) billing codes. The use of these ICD codes can lead to misclassification of diagnosed conditions. Prior to this report, all prevalence estimates were based on the number of unique children reported to ABDR with an ICD code representing a specified condition regardless of case confirmation status.
The estimates in this report were derived by conducting medical record review and case confirmation of a random sample of cases of the condition reported to ABDR. The confirmation probability from the sample was used to develop informed estimates of the actual diagnosed defect prevalence. See Defect prevalence calculation.
For explanations of table columns see Column descriptions.
Prevalence
Edwards syndrome is the second most common Trisomy occurring in about 3.02 (95% CI 2.86–3.18) out of every 10,000 live births in the United States.This results in about 1,100 babies diagnosed with Edwards syndrome nationally each year.[5], [6]
In Alaska, during 2007-2021, the prevalence of Edwards syndrome was 1.1 per 10,000 live births.| Reports | Defects | Births | Prevalence (95% CI) |
|---|---|---|---|
| 30 | 17.5 | 162989 | 1.1 (0.7, 1.7) |
| Notes: 95% CI = 95% Confidence Interval | |||
Trend
Prevalence per 10,000 births of Edwards syndrome during 2007-2021 by five-year moving averages, with 95% confidence interval band and Poisson estimated fitted line.| Estimate | Std. Error | t value | Pr(>|t|) |
|---|---|---|---|
| -0.08657 | 0.03286 | -2.63486 | 0.02714 |
| Notes: 95% CI = 95% Confidence Interval | |||
Regional Distribution
Distribution of Edwards syndrome in Alaska by Public Health Region of maternal residence at the time of birth. A description of regional breakdowns can be found here. Data suppressed for # of reports < 6.Demographics
Some subgroups may be more at risk for having a baby with Edwards syndrome. This section provides the descriptive epidemiology of specified maternal, birth, and child characteristics identified from the birth certificate.
Accompanying Diagnoses
The ten diagnoses most commonalty associated with Edwards syndrome.
Technical notes
Column descriptions
# Reports: Unless otherwise noted, the number of unique reports of the defect received by ABDR during the specified birth year(s). Each report represents a unique child with the specified defect.
# Defects: The estimated true number of reports that are diagnosed defects based on medical record review and case confirmation.
# Births: The number of live births among Alaskan residents that occurred in Alaska during the specified birth year(s).
Prevalence (95% CI): The estimated diagnosed prevalence of the condition and corresponding 95% Confidence Interval. (For information on how the defect prevalence was estimated see below).
Defect prevalence calculation
The estimated defect prevalence was calculated using a Bayesian approach based on the reported prevalence, PPV and 1-NPV (see formula below).
Through medical records review and case confirmation of a random sample of reported cases, the defect prevalence is calculated as:
\[PPV (Positive Predictive Value) = p(defect|report)\] \[NPV (Negative Predictive Value) = p(\overline{defect}|\overline{report})\]
\[p(defect) \approx [p(report)\cdot PPV]+[p(\overline{report})\cdot (1-NPV)]\]
Defect prevalence estimates are a more accurate estimation of the actual diagnosed prevalance of birth defects compared to the reported prevalance estimates in Alaska. ABDR obtains reports from medical providers using International Classification of Disease (ICD) codes that are extracted from individual systems which when aggregated may not reflect true diagnostics. Caution should be used when interpreting and comparing the reported prevalence estimates with national estimates.
See Data analysis methods for more information.
P-value estimate
To evaluate the trend over time and account for under/over-dispersion we constructed a quasi-Poisson regression model. This model assumes the variance is a linear function of the mean and models the estimated number of annual defects by year with a natural log (ln) offset of the annual births. P-values < 0.05 are considered significant, which indicates that the predicted slope is significantly different from a slope of zero.
Data suppression
For region and demographic data tables, values are suppressed based on the number of reports received during the observation period. Counts less than 6 are suppressed (as indicated by ‘-’ in the table). For regions or demographics with only one cell count suppressed a second is suppressed to eliminate the ability to back-calculate the estimate.
References
[1] NIH U.S. National Library of Medicine. Genetics Home Reference: Trisomy 18, https:// ghr.nlm.nih.gov/condition/trisomy-18.pdf; 2017 [accessed 02.27.2017]
[2] Cereda A, Carey JC. The trisomy 18 syndrome. Orphanet Journal of Rare Diseases. 2012;7(81)
[3] Witters I, Van Robays J, Willekes C et al. Trisomy 12,18, 21, Triploidy and Turner syndrome: the 5T’s. Look at the hands. Facts, Views & Vision in ObGyn 2011; 3(1): 15-21.
[4] Loane M, Morris J et al. Twenty-year trends in the prevalence of Down syndrome and other trisomies in Europe: impact of maternal age and prenatal screening. European Journal of Human Genetics. 2013; 21: 27-33
[5] Centers for Disease Control and Prevention, Birth Defects Data and Statistics, https://www.cdc.gov/ncbddd/birthdefects/data.html; 2016 [accessed 02.27.2017]
[6] Mai CT, Isenburg JL, Canfield MA, Meyer RE, Correa A, Alverson CJ, Lupo PJ, Riehle‐Colarusso T, Cho SJ, Aggarwal D, Kirby RS. National population‐based estimates for major birth defects, 2010–2014. Birth Defects Research. 2019; 111(18): 1420-1435
Resources
Trisomy 18 Foundation
International
Trisomy 13/18 Alliance: Preparing for your baby’s arrival
National Birth Defects
Prevention Network
Suggested Citation
State of Alaska Department of Health and Social Services, Division of Public Health, Section of Women’s, Children’s, and Family Health. Alaska Birth Defects Registry Condition Report: Trisomy 18, Alaska, 2007-2021. Updated April 11, 2024. Available at: http://rpubs.com/AK_ABDR/Trisomy18.
Contact
Alaska Birth Defects Registry (ABDR)
3601 C Street, Suite 358
Anchorage, AK 99503
(907) 269-3400 phone
(907) 754-3529 fax
hssbirthdefreg@alaska.gov
Updated: April 11, 2024
Code source:
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