Congenital Malformations Registry - Summary Report

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

Introduction

The CMR relies on reports from hospitals and physicians for case ascertainment. Underreporting is an obvious concern, and the CMR over the years has developed methods to improve case ascertainment and monitor hospital reporting (Appendix 3). In this section, CMR live birth prevalences are compared with the national prevalence estimates for 21 selected defects developed by the Centers for Disease Control and Prevention (CDC) and the National Birth Defects Prevention Network (NBDPN).1 The 21 defects were selected as they are generally diagnosed soon after birth and the accuracy of diagnosis should be similar across sites1.These estimates were based on 11 registries which use active case-finding. Active case-finding uses data collection specialists who go to hospitals to identify and abstract records of children with malformations. The active case-finding systems were chosen as they have similar methodology and prevalence estimates are usually higher in systems using active case finding, although variation was observed even among the 11 active case finding systems (See Figure 2 in Parker1).

As can be seen from Table 1, the CMR prevalences are equal to or higher than the lower boundary of the actual range of the 11 registries for 16 of the 21 defects (bold prevalences). The prevalences are generally higher for New York State excluding New York City than for New York City (17 defect prevalences are equal to or higher than the lower boundary of the actual range of the 11 registries compared to 12 for New York City).

The interpretation of differences among registry prevalences is difficult. The lower prevalences of the CMR for neural tube defects (spina bifida with anencephalus), and trisomy 18 is most likely due to the lack of reports on terminations as termination rates for these conditions are high. The lower rates in limb reduction and gastroschisis are also more difficult to explain as these are also easily recognizable defects. We have noted that the rate for lower limb reduction deformity has been declining over several years and plan to examine defect trends in a future report.

Several registries would have the highest prevalence for one defect and the lowest prevalence for others. Variation among the registries in the rates of specific defects could reflect demographic differences in the populations as there are racial and ethnic differences in the rates of specific birth defects1. 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. However, the source(s) of much of the variation is unclear and there may 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.2

CMR staff will continue their efforts to improve reporting (see Appendix 3) and will track our progress using the NBDPN national prevalence estimates.

Section V - Table 1: Prevalence* of Selected Major Birth Defects in New York State
(Birth years: 2004-2006)
Birth Defect Category New York City Upstate New York New York State NBDPB 2004-2006
Anencephalus 0.4 0.6 0.5 2.2
Spina bifida without anencephalus 2.1 2.2 2.2 3.7
Encephalocele 0.5 0.5 0.5 0.8
Anophthalmia/ microphthalmia 0.9 1.5 1.3 2.1
Common truncus 0.9 0.7 0.8 0.7
Transposition of great arteries 4.0 4.7 4.4 3.0
Tetralogy of Fallot 4.9 4.9 4.9 4.1
Endocardial cushion defect 2.7 3.0 2.9 4.7
Hypoplastic left heart syndrome 2.2 2.9 2.5 2.3
Cleft palate without cleft lip 5.1 6.6 5.9 6.5
Cleft lip with and without cleft palate 6.1 8.7 7.4 10.9
Esophageal atresia/ tracheosophageal fistula 2.5 2.4 2.4 2.1
Rectal and large intestinal atresia/stenosis 4.1 4.3 4.2 4.9
Reduction deformity, upper limbs 1.4 2.2 1.8 3.6
Reduction deformity, lower limbs 0.8 0.9 0.8 1.7
Gastroschisis 1.5 3.1 2.3 4.7
Omphalocele 1.2 1.6 1.4 1.9
Diaphragmatic hernia 2.0 3.4 2.7 2.6
Trisomy 13 1.1 1.0 1.0 1.2
Down syndrome(trisomy 21) 11.4 13.3 12.4 13.5
Trisomy 18 1.0 1.1 1.0 2.6

*Prevalence (number of defects per 10,000 live births)

References

  1. Parker SE, Mai CT, Canfield MA, Rickard R, Wang Y, Meyer RE, Anderson P, Mason CA, Collins JS, Kirby RS and Correa A Updated national birth prevalence estimates for selected birth defects in the United States, 2004–2006. Birth Defects Research Part A: Clinical and Molecular Teratology, n/a. doi: 10.1002/bdra.20735
  2. 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.