Birth Defects Surveillance System Research Articles

Descriptive epidemiology of holoprosencephaly and arhinencephaly in metropolitan Atlanta, 1968-1992.

We report the descriptive epidemiology of holoprosencephaly and arhinencephaly using data from the Metropolitan Atlanta Congenital Defects Program, a population-based birth defects surveillance system with multiple sources of ascertainment. From 1968-1992, we ascertained 63 cases of holoprosencephaly and arhinencephaly from approximately 734,000 births, for a birth prevalence of 0.86 per 10,000. Thirteen case infants with holoprosencephaly and four case infants with arhinencephaly were categorized as having syndromes. Of the case infants with non-syndromic holoprosencephaly, 55% had malformations not attributable to the underlying brain defect. The rate of holoprosencephaly and arhinencephaly increased from 0.58 per 10,000 during 1968-1972 to 1.2 per 10,000 during 1988-1992 (P for trend = 0.016). Rates were higher for females than for males (risk ratio = 1.45, 95% C.I. 0.88-2.41) and higher for nonwhites than for whites (risk ratio = 1.74, 95% C.I. 1.06-2.86). There was a U-shaped distribution of risk associated with maternal age with a slightly increased risk for younger women (risk ratio for maternal age < 20 years, compared with age 25-29 years = 1.68, 95% C.I. 0.77-3.62) and older women (risk ratio for maternal age > 34 years, compared with age 25-29 years = 2.30, 95% C.I. 0.93-5.7), but this was not statistically significant. The increased risk in the older age group could be largely explained by the presence of cases with autosomal trisomies. Neonatal mortality was higher for infants with malformations that were not attributable to the underlying brain defect and for infants with syndromes than for infants with isolated holoprosencephaly. This analysis is the first population-based study with long-term data on this rare defect. Further epidemiologic studies will be necessary to assess the risk factors for holo-prosencephaly and arhinencephaly.

Trends and Outcomes After Prenatal Diagnosis of Congenital Cardiac Malformations by Fetal Echocardiography in a Well Defined Birth Population, Atlanta, Georgia, 1990–1994

In this study we used a population-based approach to assess the impact of fetal echocardiography on a well defined birth population with nearly complete ascertainment of cardiac defects. Although fetal echocardiography is being used more frequently in the prenatal diagnosis of congenital cardiac malformations, its impact on the diagnosis and surveillance of cardiac defects has not been described in defined populations. All stillborn and live-born infants with diagnosed cardiac defects and whose mothers resided in the metropolitan Atlanta area from January 1990 through December 1994 were ascertained through an established birth defects surveillance system. All fetuses with cardiac defects diagnosed prenatally by a pediatric of cardiac defects, diagnostic trends and adverse fetal outcomes were described. We identified 1,589 infants with congenital cardiac malformations, for a live-birth prevalence rate of 8.1/1,000 (95% confidence interval [CI] 7.8 to 8.6). Overall, 97 (6.1%) of these cases of cardiac malformations were diagnosed prenatally. The proportion of cardiac defects diagnosed prenatally rose from 2.6% in 1990 to 12.7% in 1994, a nearly fivefold increase. The proportion of cardiac defects diagnosed prenatally during the study varied by the type of defect, from a low of 4.7% for atrial septal defects to a high of 28% for hypoplastic left heart syndrome. Prenatally diagnosed cardiac malformations were associated with a high incidence of infant mortality (30.9%, 95% CI 2.4 to 5.4) and fetal wastage (17.5%, 95% CI 6.2 to 11.3). These data show that fetal echocardiography is being used increasingly in the prenatal diagnosis of congenital cardiac malformations in metropolitan Atlanta. Few pregnancy terminations were reported as a result of such diagnoses. However, the study had limited power (10%) to detect a meaningful decrease in birth prevalence rates for congenital heart disease. In addition, survival of infants was not improved after prenatal diagnosis with fetal echocardiography.

No Evidence of Increase in Birth Defects and Health Problems among Children Born to Persian Gulf War Veterans in Mississippi

The Department of Veterans' Affairs, Jackson, Mississippi, and the Mississippi State Department of Health conducted a collaborative investigation of an apparent increase in the numbers of birth defects and other health problems among children born to veterans of two Mississippi National Guard units who had served in the Persian Gulf War. The medical records of all children conceived by and born to veterans of the two units after deployment were reviewed; observed numbers of birth defects and other health problems were compared with expected numbers using rates from birth defect surveillance systems and previous surveys. The total number of all types of birth defects was not greater than expected, but whether the number of specific birth defects was greater than expected could not be determined. The frequency of premature birth, low birth weight, and other health problems appeared similar to that in the general population.

Early Childhood Surveillance of Developmental Disorders by a Birth Defects Surveillance System

The prevalence of developmental disabilities in early childhood is not well documented. An established birth defects registry extended surveillance to identify cases of developmental disorders in early childhood by adding all known sources of diagnosis and service to case-finding methods. Residents of a northwest Arkansas region born during 1985 to 1987 and diagnosed with either a birth defect or a developmental disorder by the 4th birthday comprised the studied cohort. Case records were linked with death certificates to examine the influence of mortality on prevalence ratios. Prevalence ratios estimated were 64.5/1000 resident live births (60.9/1000 among survivors to age 4 years) for either birth defect or developmental disorder, 33.4/1000 for developmental disorder, 37.0/1000 for birth defect, and 9.5/1000 for both developmental disorder and birth defect. Prevalence ratios of specific developmental disorders and the role of mortality in decreasing population prevalence are reported. The most common diagnostic categories in this age group were developmental delay, seizures, and failure to thrive. Overlap of birth defect categories with a diagnosed developmental disability was examined; 68.8% of children diagnosed with neural tube defects and 45.5% of those with chromosomal abnormalities who survived to age 4 years had clinically diagnosed developmental disorders. An anticipated high degree of overlap (77%) for other central nervous system defects was found. For other birth defect categories, developmental disorder diagnosis was present in 20 to 30% of the study group. Death before age 4 years occurred most often when the diagnosis was newborn seizures (17.1%) or "conditions of the brain" (13.6%); the mortality rate was 6 to 8% for epilepsy or seizure disorders, mental retardation, and vision loss. The large number of developmental diagnoses among this cohort indicates that surveillance of these disorders in early childhood, even with tentative diagnoses, is feasible. Data obtained indicate that many birth defects are associated with developmental disorders; potentially, this association can contribute to earlier identification of developmental disorders in childhood.

Deaths associated with renal agenesis: A population‐based study of birth prevalence, case ascertainment, and etiologic heterogeneity

We report on deaths associated with renal agenesis among 211,704 consecutive births. Sources included birth and death certificates and an active birth defects surveillance system. Medical review and classification of cases were performed for 1985-1990 events. Sixty-one cases of renal agenesis were identified, and review of records was possible for 59 of the 61 cases. Of these 59 cases, 36 (61%) were confirmed, 5 (8%) were questionable, and 18 (31%) were incorrectly coded. The prevalence of confirmed cases is thus estimated at 17/100,000 births (14.2/100,000 births, excluding elective terminations and fetal deaths). Records incorrectly coded were most often those with multicystic dysplasia. Approximately one-third of cases was found by the birth defects surveillance system alone, confirming the utility of this data source for prevalence estimates. Isolated renal agenesis accounted for 44% of confirmed cases; other diagnoses included VATER association (19%), unrecognized multiple malformation syndromes (17%), exstrophy of the cloaca sequence (14%), and chromosome disorders (6%). Based on these data, prevalence rates for ICD code 753.0 and death include overascertainment of cases from erroneous coding of multicystic dysplasia and underascertainment of cases with unilateral renal agenesis associated with other malformations. Population-based ascertainment of cases by active surveillance methods and rigorous diagnostic coding standards are required to improve the accuracy of these rates. Targeted investigations of distinct subclassifications will be necessary to identify specific etiologic factors.

Descriptive epidemiology of small intestinal atresia, Atlanta, Georgia.

To describe the epidemiology of small intestinal atresia (SIA) in Atlanta, Georgia, from 1968 through 1989, we used the Metropolitan Atlanta Congenital Defects Program, an active, population-based surveillance system for birth defects diagnosed during the first year of life. We identified 176 infants with SIA, a prevalence of 2.8 per 10,000 livebirths. Among black infants, the prevalence was 3.7 per 10,000 livebirths, significantly higher than the prevalence of 2.4 per 10,000 among white infants [relative risk (RR) = 1.6, 95% confidence interval (CI) = 1.1,2.1]. Nine infants were each one member of a unique pair of twins. The prevalence among twin infants was 7.3 per 10,000, significantly higher than the prevalence of 2.8 per 10,000 among singletons (RR = 2.7, 95% CI = 1.4,5.2). Forty-nine percent of the infants had duodenal atresia, 36% had jejunal atresia, and 14% had ileal atresia. Two infants (1%) had atresia at an unspecified site in the small intestine. We grouped the infants by anatomic location of SIA into four categories: isolated SIA (53%), SIA with multiple unrelated defects (21%), sequences (16%), and syndromes (10%). We then compared the isolated and multiple unrelated defects groups by gender, race, maternal age, birth weight and one-year mortality for each location of SIA. Among black infants the prevalence of isolated jejunal atresia was 1.4 per 10,000, significantly higher than the prevalence of 0.2 per 10,000 among white infants (RR = 6.3, 95% CI = 2.9, 13.5). The increased prevalence of these defects among twins was a particularly interesting finding.

Interaction between epidemiology and laboratory sciences in the study of birth defects: design of birth defects risk factor surveillance in metropolitan Atlanta.

Despite years of research, the etiology of most birth defects remains largely unknown. Interview instruments have been the major tools in the search for environmental causes of birth defects. Because of respondents' problems with recognition and recall, interviews are limited in their capacity to measure certain exposures. Laboratory scientists can have a major impact on defining markers of environmental exposure and genetic susceptibility. The Centers for Disease Control is starting a case-control study of serious birth defects on the basis of a population-based surveillance system for birth defects diagnosed during the first year of life in metropolitan Atlanta. Each year, 300 infants with selected birth defects (case subjects) and 100 population-based control subjects (infants without birth defects) will be enrolled in an ongoing study that will supplement surveillance. In addition to conducting extensive maternal interviews, we will collect blood and urine specimens from case and control subjects and their mothers for laboratory testing. Eventually, some environmental sampling may be incorporated. Particular areas of emphasis are (1) nutritional factors, specifically measuring maternal folic acid levels and other micronutrients (e.g., zinc) to explore their role in the etiology of neural tube defects, (2) substance use, specifically measuring cocaine metabolites in the blood and urine to explore their role for specific vascular disruption defects, and (3) environmental factors such as pesticides and aflatoxins, to explore their potential relationships with specific defects. In addition, a DNA bank will be maintained to evaluate the role of specific candidate genes in the etiology of birth defects. The development and testing of these methods could be useful to assess the interaction between environmental exposures and genetic susceptibility in the etiology of birth defects.

Improved ascertainment of cardiovascular malformations in infants with Down's syndrome, Atlanta, 1968 through 1989. Implications for the interpretation of increasing rates of cardiovascular malformations in surveillance systems.

Several birth defects surveillance systems have shown an upward trend in the birth prevalence of several congenital cardiovascular malformations. Improvements in clinical ascertainment have been suggested as an explanation for this increase. For several decades, 40-50% of infants with Down's syndrome have been reported to have cardiac defects associated with the unbalanced genotype. Therefore, secular changes in the frequency of ascertained cardiovascular malformations among infants with Down's syndrome in surveillance systems could shed light on improvements in the ascertainment of these defects. The authors examined changes in the frequency of ascertained cardiovascular malformations among 532 cases of Down's syndrome recorded in the Metropolitan Atlanta Congenital Defects Program from 1968 through 1989. Overall, 33% of the cases have reported cardiovascular malformations. However, the frequency of these defects in Down's syndrome infants increased dramatically from about 20% in the early 1970s to more than 50% in the late 1980s (p = 0.0001). This upward trend was seen for all major categories of cardiac defects and persisted after the cases were stratified by race, sex, maternal age, hospital of birth, birth weight, and gestational age. These results show improvement in the ascertainment of cardiovascular malformations among Down's syndrome infants in a surveillance population. They are also consistent with the hypothesis that the increasing rates of cardiac defects are related, at least in part, to improved ascertainment of these defects in the population.

Spina Bifida Incidence at Birth—United States

Spina bifida, a birth defect of the spinal column that can cause varying degrees of paralysis, is a major contributor to serious developmental disabilities in the United States. To determine the incidence and descriptive epidemiology of spina bifida, CDC analyzed reports from 16 states with population-based birth defects surveillance systems (Table 1). This report summarizes findings from this analysis for 1983-1990.(ABSTRACT TRUNCATED AT 250 WORDS)

The Changing Epidemiology of Neural Tube Defects

To describe the recent trends and epidemiologic characteristics of neural tube defects in the United States. Ongoing surveillance data. Two birth defect surveillance systems: the nationwide Birth Defects Monitoring Program and the Metropolitan Atlanta (Ga) Congenital Defects Program for 1970 through 1989 and 1968 through 1989, respectively. Between 1970 and 1989, using discharge diagnoses of approximately 1 million live-born and stillborn infants per year, the Birth Defects Monitoring Program identified 15,503 cases of spina bifida and anencephaly. Between 1968 and 1989, using discharge diagnoses and clinical records until age 1 year of 38,000 infants per year, the Metropolitan Atlanta Congenital Defects Program identified 800 cases of spina bifida and anencephaly. None. Nationwide, neural tube defect rates have declined from 1.3 per 1000 births in 1970 to 0.6 per 1000 births in 1989. In Atlanta, neural tube defect rates have declined from 2.0 per 1000 births in 1968 to 0.6 per 1000 births in 1989. Several changes in the epidemiologic characteristics of neural tube defects were observed: (1) the proportion of spina bifida cases has increased; (2) the proportion of neural tube defect cases compared with the proportion of other unrelated defects has increased; (3) the race ratio of whites to other races for isolated neural tube defect cases has declined in Atlanta; and (4) the rate of isolated neural tube defects in females has also decreased. The declining rates of neural tube defects can be partially explained by increased widespread prenatal diagnostic techniques, strongly suggesting the role of environmental factors in neural tube defects. In particular, the use of multivitamins and folic acid to prevent the occurrence of neural tube defects needs further evaluation. Nevertheless, the changing clinical and epidemiologic characteristics of cases over time points to the etiologic heterogeneity of these conditions.

Patterns and trends of multiple congenital anomalies in birth defects surveillance systems

Infants with multiple congenital anomalies (MCA) can provide important clues in the detection of teratogenic agents. Definition, classification, and ascertainment of MCA vary, however. We present comparative epidemiologic data on MCA from two U.S. surveillance systems: the Metropolitan Atlanta Congenital Defects Program, which ascertains major birth defects during the first year of life, and the Birth Defects Monitoring Program, a nationwide system that relies on newborn hospital-discharge diagnoses. This system has two components: the Commission on Public Hospitals Activities (CPHA) and the McDonnell Douglas Health Information System (MDHIS). Our analyses were based on over 600,000 births occurring in Atlanta, and over 5 million births occurring nationwide. Infants were classified as having MCA if they had two or more major defects from different categories (central nervous system, eye, orofacial, gastrointestinal, cardiovascular, genitourinary, and musculoskeletal). Additional analyses were also done on infants with three or more defects. Compared with the nationwide system, Atlanta showed 1) a much higher rate of MCA (16.2 per 10,000 births vs. 4.9 and 3.8 per 10,000 births in CPHA and MDHIS, respectively) and 2) a higher rate of MCA with chromosomal syndromes (2.0 per 10,000 births vs. 0.6 and 0.3 per 10,000 births in CPHA and MDHIS, respectively). Moreover, in Atlanta, the proportion of MCA with recorded chromosomal syndromes increased substantially during 20 years. These data point to differences in the ascertainment of MCAs in birth defects surveillance systems. More effort is needed to improve the ascertainment and comparability of MCA in surveillance systems, an important step toward better detection of human teratogens.

Etiologic heterogeneity of neural tube defects: clues from epidemiology.

The epidemiology of neural tube defects was reviewed, using data from two birth defects surveillance systems: the nationwide Birth Defects Monitoring Program and the Metropolitan Atlanta Congenital Defects Program, for 1970-1978 and 1968-1979, respectively. After excluding cases with recognized causes, neural tube defects were divided into two major groups: "singles" and "multiples," depending on the presence of associated major defects. Only singles, which accounted for the majority of cases, were shown to have the well-known epidemiologic characteristics of neural tube defects: marked predominance of females and whites, geographic variation with an east-to-west gradient, and decreasing rates over time. On the other hand, multiples had no excess of females and occurred less predominantly in whites; moreover, their rates showed no geographic variation and little or no downward trends over time. The presence of associated defects indicates that neural tube defects are epidemiologically and probably etiologically heterogeneous. It is suggested that analytic studies of neural tube defects may be more rewarding if they try to identify different risk factors associated with various subgroups. This approach to the study of birth defects may provide better clues to their etiology and pathogenesis.

Congenital malformations surveillance: two American systems.

As part of its epidemiologic studies of congenital malformations, the Centers for Disease Control (CDC) conducts two birth defects surveillance systems in the United States. The Metropolitan Atlanta Congenital Defects Programme (MACDP) is an intensive surveillance system using several methods to identify infants born with birth defects in the Atlanta area. The Birth Defects Monitoring Programme (BDMP) is a nationwide surveillance system that monitors 1 million births per year, about a third of all births in the U.S. It relies on diagnoses from newborn discharge summaries to ascertain affected infants. The systems were originally designed to detect potential 'epidemics' of birth defects that could occur following the widespread dissemination of new teratogens similar to thalidomide. In addition to monitoring, they have also proved to be useful resources for a variety of studies of the epidemiology of birth defects.

IS THERE AN EPIDEMIC OF VENTRICULAR SEPTAL DEFECTS IN THE U.S.A.?

In the past 10 yr the reported incidence of ventricular septal defect (VSD) has increased more than two-fold in two American birth-defects surveillance systems—the Metropolitan Atlanta Congenital Defects Program and the nationwide Birth Defects Monitoring Program. To test the hypothesis that this increase was caused by improved clinical diagnosis, resulting in the diagnosis of minor VSDs, we conducted a follow-up investigation of infants with VSD in the Atlanta area. We compared the rate of spontaneous closure by 1 yr of age of VSDs diagnosed during 1970-72 with the closure rate during 1975-76. If the recently increased incidence was caused entirely by better diagnosis of minor defects that are likely to close spontaneously, we would have expected a much higher rate of spontaneous closure in the later period. In fact, the rate of spontaneous closure by 1 yr was almost identical for both periods (23·8% and 23·9%). The considerable recent increase in the reported incidence of VSD cannot be simply due to better diagnosis.

Birth defects surveillance system of five Japanese Red Cross Lying-in Hospitals in Tokyo

Birth defects surveillance system of five Japanese Red Cross Lying-in Hospitals in Tokyo

An epidemiological study of congenital reduction deformities of the limbs.

A retrospective study that was undertaken to determine why more infants had been born with congenital reduction deformities of the limbs is reported. The increase was detected by the Congenital Anomaly Surveillance System in 1969. Ninety-three infants born in Alberta and British Columbia in 1969-71 with congenital reduction deformities were matched with 93 normal infants and 93 infants with congenital malformations of a different type. The mothers of all infants were interviewed to obtain information on factors thought relevant to the establishment of a causal relationship. Although there were some significant differences between cases and normaland/or abnormal controls, this number of differences might have been expected by chance. No single causal relationship was established.