Role of geographic information systems in birth defects surveillance and research

BACKGROUND: With the significant advancement of geographic information systems (GIS), mapping and evaluating the spatial distribution of health events has become easier. We examine the role of GIS in birth defects surveillance and research. METHODS: We briefly describe the geocoding process and potential problems in accuracy of the obtained geocodes, and some of the capabilities and limitations of GIS. We illustrate how GIS has been applied using the Metropolitan Atlanta Congenital Defects Program geocoded dataset. We provide some comments on potential data quality and confidentiality issues with birth defects in relation to GIS. RESULTS: It is desirable to geocode addresses using a multistrategy approach to achieve a high-quality and accurate GIS dataset. Beyond the basic but important function of mapping, sophisticated statistical approaches and software are available to analyze the spatial or spatial-temporal occurrence of birth defects, alone or in association with environmental hazards, and to present this information without compromising the confidentiality of the subjects. CONCLUSIONS: We recommend a broad and systematic use of GIS in birth defects spatial surveillance and research.     

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.     

Epidemiological surveillance of birth defects compatible with thalidomide embryopathy in Brazil

The thalidomide tragedy of the 1960s resulted in thousands of children being born with severe limb reduction defects (LRD), among other malformations. In Brazil, there are still babies born with thalidomide embryopathy (TE) because of leprosy prevalence, availability of thalidomide, and deficiencies in the control of drug dispensation. Our objective was to implement a system of proactive surveillance to identify birth defects compatible with TE. Along one year, newborns with LRD were assessed in the Brazilian hospitals participating in the Latin-American Collaborative Study of Congenital Malformations (ECLAMC). A phenotype of LRD called thalidomide embryopathy phenotype (TEP) was established for surveillance. Children with TEP born between the years 2000-2008 were monitored, and during the 2007-2008 period we clinically investigated in greater detail all cases with TEP (proactive period). The period from 1982 to 1999 was defined as the baseline period for the cumulative sum statistics. The frequency of TEP during the surveillance period, at 3.10/10,000 births (CI 95%: 2.50-3.70), was significantly higher than that observed in the baseline period (1.92/10,000 births; CI 95%: 1.60-2.20), and not uniformly distributed across different Brazilian regions. During the proactive surveillance (2007-2008), two cases of suspected TE were identified, although the two mothers had denied the use of the drug during pregnancy. Our results suggest that TEP has probably increased in recent years, which coincides with the period of greater thalidomide availability. Our proactive surveillance identified two newborns with suspected TE, proving to be a sensitive tool to detect TE. The high frequency of leprosy and the large use of thalidomide reinforce the need for a continuous monitoring of TEP across Brazil.     

Pilot test of prenatal surveillance for birth defects in South Texas

BACKGROUND: The Texas Birth Defects Registry (TBDR) does not access prenatal diagnostic facilities to ascertain cases. Objectives of the study were to determine how many cases may be missing from the registry as a result, and to assess the feasibility and utility of prenatal surveillance for birth defects, through a pilot test in one region of Texas. METHODS: A trained abstractor reviewed medical records of all patients with abnormal ultrasound findings during 2004 in all prenatal diagnostic facilities in Texas Health Region 11 (n = 6 facilities). When birth defects were prenatally detected, demographic and diagnostic data were abstracted. Prenatal abstractions were matched to cases in the TBDR. Those that did not match to registry cases were matched to vital records to determine where and when the pregnancy ended; delivery hospital medical records were reviewed for these cases. RESULTS: Approximately 760 patient charts were reviewed at prenatal diagnostic facilities and 365 were abstracted. Of these, 165 (45%) matched to cases in the TBDR. Delivery medical records were located and reviewed for 177 prenatal abstractions, with 170 (47%) indicating at delivery no defects monitored by the registry. Delivery records for one (0.3%) prenatal abstraction were not found by the hospital. Date and place of delivery were unknown for 22 (6%) prenatal abstractions. Only eight additional infants and fetuses (one twin pair) eligible for the registry were identified. CONCLUSIONS: For Texas Health Service Region 11, it is not necessary to conduct surveillance in prenatal diagnostic facilities, and to do so would be very labor-intensive.     

Sex differences in the prevalence of human birth defects: a population-based study.

BACKGROUND: Sex differences in the prevalence of several human birth defects have often been reported in the literature, but the extent of sex differences for most birth defects is unknown. To determine the full extent of sex differences in birth defects in a population, we examined population-based data from the Metropolitan Atlanta Congenital Defects Program (MACDP). METHODS: MACDP records were analyzed for 1968 through 1995. We determined the sex-specific prevalence of all major birth defects, using the total number of live births by sex during these years as the denominator. For each specific defect, we calculated a relative risk with regard to sex on the basis of the ratio of prevalence among males to prevalence among females. Male-female relative risks were also determined for total major birth defects and for several broad categories of defects. RESULTS: The overall prevalence of major defects at birth was 3.9% among males and 2.8% among females. All but two of the major categories of birth defects (nervous system defects and endocrine system defects) had a higher prevalence among males. Defects of the sex organs were eight and one-half times more prevalent among males and accounted for about half of the increased risk of birth defects among males relative to females. Urinary tract defects were 62% more prevalent among males, and gastrointestinal tract defects were 55% more prevalent among males. Among specific defect types, twofold or greater differences in prevalence by sex were common. CONCLUSIONS: Our data indicate that sex differences in the prevalence of specific human birth defects are common, and male infants are at greater risk for birth defects than female infants. Several mechanisms have been proposed to account for these differences.     

The use of dysmorphology in birth defects epidemiology.

Most human teratogens have been identified by the clinical recognition of characteristic patterns of congenital anomalies among children whose mothers were exposed to a particular agent during pregnancy. Although this dysmorphologic method has been valuable, it is criticized because it is not easily amenable to statistical evaluation. Conventional birth defects epidemiological studies are designed to permit rigorous statistical assessment, but such investigations usually classify congenital anomalies without adequate consideration of their known etiological heterogeneity. It is possible to combine the best aspects of these two approaches to identifying human teratogens in a "dysmorphologic case/control study." Instead of including all available cases with a given defect, only individuals having the anomaly in the context of a multiple congenital anomaly pattern without a recognizable cause would be selected for inclusion among the case group. The frequency of exposure to the putative teratogen would be determined among these selected cases and among appropriately chosen controls; conventional statistical analysis would then be performed. Although this design reduces the size of the case group compared to a conventional case/control study, the statistical power is unchanged or increased. In addition, biological plausibility is increased by concentrating upon a group of cases that is more likely to have a teratogenic cause.     

Archeological dendrochronology in the southwestern united states

Dendrochronology, the science of tree‐ring dating, is the most accurate and precise nondocumentary dating method available to researchers studying the recent past. Tree‐ring dates are accurate and precise to the year and sometimes the season, and have no associated statistical uncertainty or standard error. Other prominent archeological dating techniques that use natural materials (for example, radiocarbon and archeomagnetism) have been calibrated using dendrochronological samples. 1 It is this precision and accuracy that has allowed archeologists working in the southwestern United States to construct the most detailed chronologies in the world, and to explore a plethora of environmental, social, and behavioral questions regarding past human adaptation to the region.