Background

Omphalocele, like gastroschisis, is a birth defect in the abdominal wall that causes an infant’s intestines and sometimes other organs (e.g. stomach and liver) to protrude outside of their body, usually through a hole next to the belly button. Unlike gastroschisis, the organs that are pushed outside the body are covered in a thin, transparent sac or membrane that hardly ever opens. This condition occurs early on in pregnancy when the intestines, which are pushed into the umbilical cord, do not go back into the belly as they should. When this happens, the intestines (and sometimes other organs) develop outside the abdomen.[1] Sometimes the part of the infant’s body that is supposed to hold these organs will not grow to its normal size because the organs are outside the body. In addition, if the sac around the organs breaks, an infection can ensue. Surgery is necessary after birth to put the exposed organs back inside the body. However, even after repair, infants may still have problems with feeding, digestion of food, and absorption of nutrients.[2]

The specific causes of omphalocele are unknown and most likely a combination of genetics and the environment. However, certain risk factors, including young maternal age, obesity, and alcohol and tobacco use during pregnancy, have been shown to increase the chances of having a child with omphalocele.[3,4,5]

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

Omphalocele occurs in 1.9 out of every 10,000 live births in the United States. This results in about 775 babies diagnosed with omphalocele nationally each year.[6]

In Alaska, during 2007-2015, the prevalence of omphalocele was 2.8 per 10,000 live births.
Reports Defects Births Prevalence (95% CI)
Total 152 28.5 101978 2.8 (1.9, 4.0)
Notes: 95% CI = 95% Confidence Interval

Trend

Prevalence per 10,000 births of omphalocele during 2007-2015 by three-year moving averages, with 95% confidence interval band and Poisson estimated fitted line.
Reports Defects Births Prevalence (95% CI) Predicted Prevalence†
2007-2009 16.7 3.1 11261.7 2.8 (0.8, 7.3) 2.3
2008-2010 13.3 2.5 11404.0 2.2 (0.5, 6.3) 2.4
2009-2011 14.0 2.6 11404.7 2.3 (0.7, 6.8) 2.4
2010-2012 14.7 2.7 11354.0 2.4 (0.7, 6.8) 2.5
2011-2013 14.7 2.7 11349.0 2.4 (0.7, 6.8) 2.6
2012-2014 15.0 2.8 11334.7 2.5 (0.7, 6.8) 2.7
2013-2015 19.3 3.6 11377.0 3.2 (1.2, 8.1) 2.7
Notes: Each row is based on three-year moving averages; Prevalence reported per 10,000 live births; 95% CI=95% Confidence Interval

† Estimated rate based on Poisson model
The p-value test for trend detected no significant increase or decrease in the number of live births with omphalocele during 2007-2015. See p-value estimate
Estimate Std. Error t value Pr(>|t|)
0.02829 0.02453 1.15311 0.30099

Regional Distribution

Distribution of omphalocele 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.
Reports Defects Births Prevalence (95% CI)
Anchorage 73 13.7 41815 3.3 (1.8, 5.3)
Gulf Coast 9 1.7 6313 2.7 (0.4, 8.8)
Interior 11 2.1 18534 1.1 (0.3, 3.9)
Mat-Su 16 3.0 12081 2.5 (0.9, 7.3)
Northern 16 3.0 7114 4.2 (0.9, 10.2)
Southeast 8 1.5 6375 2.4 (0.4, 8.7)
Southwest 19 3.6 9746 3.6 (1.1, 9)
Notes:Prevalence reported per 10,000 live births; Data suppressed for # of reports < 6; 95% CI = 95% Confidence Interval

Demographics

Some subgroups may be more at risk for having a baby with omphalocele. This section provides the descriptive epidemiology of specified maternal, birth, and child characteristics identified from the birth certificate.

Reports Defects Births Prevalence (95% CI)
Sex
  Female 70 13.1 49462 2.6 (1.6, 4.5)
  Male 82 15.4 52516 2.9 (1.7, 4.7)
Birth weight (grams)
  <2500 57 10.6 5925 17.9 (9.3, 31.0)
  2500+ 95 17.9 95890 1.9 (1.1, 2.8)
Maternal age
  12-19 19 3.5 8043 4.4 (1.4, 10.9)
  20-24 54 10.1 28015 3.6 (2.0, 6.6)
  25-29 34 6.4 30852 2.1 (0.9, 4.2)
  30-34 34 6.4 22480 2.8 (1.2, 5.8)
  35-39 - - 10015 1.3 (0.2, 5.6)
  40+ - - 2543 -
Maternal race
  Alaska Native/American Indian 56 10.5 25801 4.1 (2.1, 7.1)
  Asian/Pacific Islander 16 3.0 9399 3.2 (0.7, 7.7)
  Black 9 1.7 4134 4.1 (0.6, 13.5)
  White 68 12.8 61287 2.1 (1.1, 3.4)
Maternal education (years)
  <12 21 3.9 9778 4.0 (1.1, 9.0)
  12 56 10.5 36724 2.9 (1.5, 5.0)
  12+ 73 13.7 52380 2.6 (1.5, 4.2)
Marital status
  Married 71 13.4 64510 2.1 (1.2, 3.5)
  Unmarried 81 15.1 37078 4.1 (2.5, 6.7)
Maternal smoking use
  Reported smoking 35 6.5 14467 4.5 (2.0, 9.0)
  Reported not smoking 116 21.8 85927 2.5 (1.6, 3.7)
Medicaid (mother or child)
  Medicaid 112 20.9 51554 4.1 (2.5, 6.0)
  non-Medicaid 39 7.4 50311 1.5 (0.7, 2.9)
Father on birth certificate
  None 6 1.1 5559 2.0 (0.4, 10.0)
  Present 146 27.4 96419 2.8 (1.9, 4.1)
Notes: Prevalence reported per 10,000 live births; Data suppressed for # of reports < 6; 95% CI = 95% Confidence Interval

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. MedlinePlus: Omphalocele, https://medlineplus.gov/ency/article/000994.htm; 2015 [accessed 02.28.2017]

[2]Centers for Disease Control and Prevention. Facts about Omphalocele, https://www.cdc.gov/ncbddd/birthdefects/omphalocele.html; 2015 [accessed 02.28.2017]

[3] Kallen, B. Abdominal Wall Defects. Epidemiology of Human Congenital Malformations 2013; 137-141

[4] Mac Bird T, Robbins JM, Druschel C, Cleves MA, Yang S, Hobbs CA. Demographic and environmental risk factors for gastroschisis and omphalocele in the National Birth Defects Prevention Study. Journal of Pediatric Surgery 2009; 44(8):1546-51

[5] Waller DK, Shaw GM, Rasmussen SA, Hobbs CA, Canfield MA, Siega-Riz AM, Gallaway MS, Correa A. Prepregnancy obesity as a risk factor for structural birth defects. Arch Pediatr Adolesc Med, 2007;161(8):745-50.

[6] Centers for Disease Control and Prevention, Birth Defects Data and Statistics, https://www.cdc.gov/ncbddd/birthdefects/data.html; 2016 [accessed 02.23.2017]

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: Omphalocele, Alaska, 2007-2015. Updated January 1, 2020. Available at: http://rpubs.com/AK_ABDR/Omphalocele07_15.

Contact

Alaska Birth Defects Registry (ABDR)
3601 C Street, Suite 358
Anchorage, AK 99503
(907) 269-3400 phone
(907) 754-3529 fax

Updated: January 1, 2020
Code source: R:\ABDR\Analysis_New\ABDR_CASECONF\cond_reports\Published_reports\Omphalocele07_15.Rmd