Congenital Malformations Registry - Summary Report

Section V
Comparison of Selected Malformation Prevalence
with Other Birth Defects Registries

Introduction to Table

The CMR relies on reports from hospitals and physicians for case ascertainment. Underreporting is an obvious concern, and the CMR monitors hospital reporting and follows up if there appears to be underreporting. In this section, CMR live birth prevalence are compared with the prevalences of two other registries, the Metropolitan Atlanta Congenital Defects Program (MACDP) and the Texas Birth Defects Monitoring Division (TBDMD).1 These two registries send data collection specialists to hospitals to identify and abstract records of children with malformations. To help evaluate possible underreporting, CMR prevalences of selected malformations, defined using BPA codes, were compared with prevalence from these two registries. (See Appendix 4 for further information on these BPA codes.) With the exception of Fetal Alcohol Syndrome (FAS) which is followed up to six years in Texas, these programs follow children through one year of age. The CMR follows children through two years; however, more than 95% of cases are reported in the first year. Most of the malformations in this table are recognized at birth. The exceptions are fetal alcohol syndrome and some cardiac malformations.

Several malformations, including tetralogy of fallot, esopheal atresia/tracheoesophageal fistula, pyloric stenosis, and cleft palate without cleft lip have similar prevalence rates among the registries indicating that the CMR's surveillance system is effective in case ascertainment for these defects.

There are, however, apparent differences among the registries in the prevalence of some malformations. Caution should be used when comparing rates from different surveillance systems. Some differences are more likely due to differences in surveillance practices. Factors that may influence prevalence rates include case ascertainment methods, sources, and case inclusion criteria. For example, the low prevalence of anencephaly in New York State when compared to the other registries is probably due to the inclusion of stillborn infants in the MACDP and TBDMD. The CMR includes only live born children (see Section VI, Current Topics).

Variation among the registries in the rates of specific defects may also reflect demographic differences in the populations. The prevalence of Down syndrome, trisomy 18 and trisomy 13 is highly dependent upon the maternal age distribution, age-specific pregnancy rates and women's use of prenatal diagnosis and pregnancy termination. The lower live birth prevalence rates of these chromosomal abnormalities in the CMR may be partially attributable to one or more of these factors.

There are also racial and ethnic differences in the rates of specific birth defects. A report from the California Birth Defects Monitoring Program (CBDMP) for the years 1983-1990 showed that whites had the highest pyloric stenosis rate, hispanics the highest rates of neural tube defects and blacks had a higher rate of heart defects than the other races 2. There may also be true geographic differences. A comparison of birth defect prevalences between the MACDP and CBDMP for the years 1983-1988 that adjusted for race, sex and maternal age showed regional differences in arm, hand and limb reduction defects 3.

Although there are differences in the rates of some specific defects presented in Table 5, these differences are not substantive.

Section V
Comparison of Selected Malformation Prevalence
With Two Other Birth Defects Registries
Malformations CMR
Anencephalus 0.4 3.4 3.0
Spina bifida without anencephalus 2.3 3.6 4.0
Hydrocephalus without spina bifida 7.2 8.2 7.4
Encephalocele 0.7 1.4 1.0
Microcephalus 4.6 7.9 6.5
Anophthalmia/microphthalmia 0.7 2.8 2.8
Common truncus 0.6 0.8 0.8
Transposition of great arteries 3.6 5.4 4.9
Tetralogy of Fallot 4.2 3.7 3.1
Ventricular septal defect 34.6 39.8 42.3
Hypoplastic left heart syndrome 1.8 3.1 2.0
Coarctation of aorta 3.8 5.5 4.4
Choanal atresia 1.5 1.5 1.2
Cleft palate without cleft lip 5.8 7.1 6.1
Cleft lip with and without cleft palate 7.1 8.4 11.1
Esophageal atresia/tracheoesophageal fistula 2.2 2.4 2.1
Rectal/large intestine atresia/stenosis 3.9 4.0 4.8
Pyloric stenosis 17.1 13.4 19.3
Hirschsprung's disease (congenital megacolon) galmmmegacolon 2.0 2.3 1.2
Biliary atresia 0.9 0.8 0.7
Renal agenesis/hypoplasia 2.9 4.4 5.2
Bladder exstrophy 0.2 0.1 0.2
Hypospadias and epispadias 33.1 32.7 27.8
Reduct deform of upper limb 1.7 4.0 4.2
Reduct deform of lower limb 1.2 1.7 1.9
Diaphragmatic hernia 1.2 2.3 2.5
Omphalocele 1.1 2.5 2.3
Gastroschisis 1.2 2.2 4.0
Down syndrome 10.6 13.0 12.2
Trisomy 13 0.8 1.4 1.2
Trisomy 18 0.2 2.6 2.3
Fetal alcohol syndrome 1.1 1.4 0.2
Amniotic bands 0.2 1.5 0.8


  1. Birth defects surveillance data from selected states, A report from the National Birth Defects Prevention Network. Birth Defects Research (Part A): Clinical and Molecular Teratology 2004; 70: 609-676.
  2. Stierman L, Birth Defects in California: 1983-1990, California Birth Defects Monitoring Program Report Series, December, 1994.
  3. Schulman J, Edmonds LD, McClern AB, et al. Surveillance for and comparison of birth defect prevelences in two geographic areas - United States 1983-1988. In: CDC Surveillance Summaries; March 19, 1993. Morbidity and Mortality Weekly Report 1993; 42(No. SS-1):1-7.