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
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 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 1 in Canfield1).
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) and five of the defects are equal to or higher than the lower 95 percent confidence interval (CI) (boxed prevalences). The prevalences are generally higher for New York State excluding New York City than for New York City (18 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 (NTD), anophthalmia/microphthalmia and trisomy 18 is most likely due to the lack of reports on terminations as termination rates for these conditions are high. The lower prevalence for cleft lip with/without cleft palate is more difficult to explain. There has been little variation in the prevalence since 1983 and it is an easily identified condition. There is also a wide variation within New York State itself from 5.4 in New York City to 13.0 in another region. The lower rates in limb reduction are also more difficult to explain as these are also easily recognizable defects. We have noted that the rate has been declining over several years, especially for lower limbs and plan to examine defect trends in a future report.
None of the 11 registries had all 21 defect prevalences fall within the 95 percent confidence intervals. 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 defec