Case ascertainment for state-based birth defects registries: characteristics of unreported infants ascertained through birth certificates and their impact on registry statistics in New York state

Maternal Chlamydia Infection During Pregnancy and Risk of Cyanotic Congenital Heart Defects in the Offspring

OBJECTIVES

Genital Chlamydia is a common bacterial sexually-transmitted infection among reproductive aged women, particularly younger populations. Cyanotic congenital heart defects (CCHDs) constitute about one quarter of all cardiac malformations at birth, and are associated with high rate of morbidity and mortality. Epidemiological research on the association between maternal Chlamydia during pregnancy and CCHDs in the offspring is lacking.

METHODS

Using data from the 2012 United States birth certificates, we examined the association between CCHDs and prenatal exposure to Chlamydia among live singleton births with CCHDs (n = 2487) and unaffected singleton births (n = 3,334,424). We estimated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) using unconditional logistic regression analysis for all CCHDs combined, and isolated CCHDs (without other major congenital malformations).

RESULTS

Overall 1.7% of case and 1.7% of control women reported having Chlamydia during their pregnancies. After controlling for potential confounders, we found a weak positive association between maternal Chlamydia during pregnancy and all CCHDs combined (aOR = 1.39; 95% CI 1.02-1.90). The positive association persisted for isolated CCHD cases, but with marginal significance (aOR = 1.34; 95% CI 0.96-1.74). Subgroup analyses for younger women showed an increased risk for CCHDs; however, the associations were not statistically significant.

CONCLUSIONS

Maternal exposure to Chlamydia during pregnancy was weakly associated with a higher risk of CCHDs in the offspring. The finding should be interpreted with caution due to limitations of birth certificate data. Future studies using more robust data sources are warranted to further study the association between maternal Chlamydia during pregnancy and CCHDs in the offspring.

The influence of misclassification bias on the reported rates of congenital anomalies on the birth certificates for West Virginia--a consequence of an open-ended query

BACKGROUND

Passive surveillance for congenital anomalies using birth certificates are generally considered to have biased reporting, though the sources of those biases are not well-known nor controlled for. We have analyzed the congenital anomaly reporting data for 418,385 live births in West Virginia (1990-2009) from the 1989 US standard birth certificate and have newly identified a particular source of bias.

METHODS

Congenital anomaly prevalence rates per 100 live births have been determined for both specified birth defects and for other congenital anomalies by county, by hospital, and by year. Extreme outliers were identified by z score. Text strings for "other congenital anomaly" reports recorded for 1998-2009 were assessed for information on congenital anomalies.

RESULTS

While rates for specified birth defects reported in checked-box format showed little variation, rates for "other congenital anomaly" collected in open-ended format showed much variation. Nearly half of the "other congenital anomaly" reports were for neonatal conditions rather than for major structural congenital anomalies. This misclassification alone had elevated the state-wide congenital anomaly reporting rate from 1.1 to 1.8% of live births. Geographic clustering and a temporal bulge in congenital anomaly reports disappeared after misclassified data were removed.

CONCLUSIONS

Data collected in checked-box format on specified birth defects showed consistent patterns over time and space, while data collected in open-ended format on "other congenital anomalies" showed an epidemiological pattern reflecting neonatal conditions rather than birth defects. The 2003 US standard birth certificate wisely limits data collection to specified birth defects using the checked-box format.

Hirschsprung's disease and variants in genes that regulate enteric neural crest cell proliferation, migration and differentiation

Hirschsprung's disease (HSCR) results from failed colonization of the embryonic gut by enteric neural crest cells (ENCCs); colonization requires RET proto-oncogene (RET) signaling. We sequenced RET to identify coding and splice-site variants in a population-based case group and we tested for associations between HSCR and common variants in RET and candidate genes (ASCL1, homeobox B5 (HOXB5), L1 cell adhesion molecule (L1CAM), paired-like homeobox 2b (PHOX2B), PROK1 and PROKR1) chosen because they are involved in ENCC proliferation, migration and differentiation in animal models. We conducted a nested case-control study of 304 HSCR cases and 1215 controls. Among 38 (12.5%) cases with 34 RET coding and splice-site variants, 18 variants were previously unreported. We confirmed associations with common variants in HOXB5 and PHOX2B but the associations with variants in ASCL1, L1CAM and PROK1 were not significant after multiple comparisons adjustment. RET variants were strongly associated with HSCR (P-values between 10(-3) and 10(-31)) but this differed by race/ethnicity: associations were absent in African-Americans. Our population-based study not only identified novel RET variants in HSCR cases, it showed that common RET variants may not contribute to HSCR in all race/ethnic groups. The findings for HOXB5 and PHOX2B provide supportive evidence that genes regulating ENCC proliferation, migration and differentiation could be risk factors for HSCR.

Surveillance of birth defects: Brazil and the US

The impacts of birth defects in the society have substantially increased over the last decades in countries where the reduction of infant mortality by other causes has occurred. Birth defects surveillance represents an important source of information for planning X health policies and resource allocation. In this article, we discuss the potential utilizations, methodology options, limitations, and policy issues related to birth defects surveillance. Also, the birth defects surveillance programs from US and Brazil are described and compared as an illustration of the development of surveillance systems in two countries with clearly dissimilar health systems and resource allocation for birth defects programs. Finally, we propose measures for the improvement of the existing systems in both countries focusing at the utilization of preexisting resources.

Reproductive outcomes among former Love Canal residents, Niagara Falls, New York

Love Canal, located in Niagara Falls, NY, and among the earliest and most significant hazardous waste sites in the United States, first came to public attention in 1978. In this study, researchers evaluated 1,799 live births from 1960 through 1996 to 980 women who formerly lived in the Love Canal Emergency Declaration Area and were of reproductive age sometime during that time period. Using Upstate New York and Niagara County as external comparison populations, standardized incidence ratios with 95% confidence intervals were calculated for low birth weight, preterm birth, small for gestational age, and congenital malformations, and unadjusted proportions of male to female births were calculated. Internal comparisons among the infants were also performed according to several measures of potential exposure using generalized estimating equations. The results indicated a statistically significant elevated risk of preterm birth among children born on the Love Canal prior to the time of evacuation and relocation of residents from the Emergency Declaration Area, using Upstate New York as the standard population (standardized incidence ratio=1.40; 95% confidence interval: 1.01, 1.90). Additionally, the ratio of male to female births was lower for children conceived in the Emergency Declaration Area (sex ratio=0.94 versus sex ratio=1.05 in the standard population) and the frequency of congenital malformations was greater than expected among Love Canal boys born from 1983 to 1996 (standardized incidence ratio=1.50 when compared to Upstate New York), although in both cases the 95% confidence interval included the null value. Finally, increased risk for low birth weight infants among mothers who lived closest to the Canal as children was found (odds ratio=4.68; 95% confidence interval: 1.24, 17.66), but this estimate was limited due to small numbers (n=4). The study adds to the knowledge of the possible reproductive effects from exposure to chemicals arising from hazardous waste; however, given the small number of some events, the qualitative nature of the exposure assessment, and possibility of spurious associations due to multiple comparisons, the findings should be interpreted cautiously.

Quality of reporting on birth defects in birth certificates: case study from a Brazilian reference hospital

The aim of this study was to evaluate the coverage, validity and reliability of Brazil's Information System on Live Births (SINASC) for birth defects in a hospital in the city of Campinas (São Paulo State). The study population consisted of 2,823 newborn infants delivered in 2004 at the Women's Integrated Health Care Center (CAISM). A birth defect registry (ECLAMC) was used as the gold-standard. All birth defect cases reported at CAISM in 2004 (92 cases) were selected from SINASC data files. All 168 birth defect cases from the same city and year registered at ECLAMC were also retrieved. An underreporting of 46.8% was observed for all birth defects, and 36.4% when considering only the major birth defects. The ascertained sensitivity and specificity were, respectively, 54.2% and 99.8%. The reliability of three and four-digit ICD-10 coding for birth defects was 0.77 and 0.55 respectively (kappa statistic). These results suggest that information provided by birth certificates in Campinas still presents limitations when seeking to ascertain accurate estimates of the prevalence of birth defects, hence indicating the need for improvements in the SINASC database to enable it to portray birth defect prevalence at birth in this city.

The relationship between congenital malformations and preterm birth

AIMS

To investigate how congenital malformations (CM) are associated with preterm (PT) births.

METHODS

A population cohort study analyzed data from the New York State Congenital Malformations Registry to look at live births from the Lower Hudson Valley Region from 2000-2003. ICD9 codes identified all cases and types of CM in addition to cases with multiple malformations. Subjects were categorized into one of three gestational age (GA) groups. Only cases with a known GA at birth were included. Poisson regression analysis established a risk ratio for children born with a CM of being born preterm.

RESULTS

The PT birth rate was 11.2% and the CM rate 3%. Children with a CM were more likely to be born PT (RR: 2.20; CI: 2.01-2.40), moderately preterm (RR: 1.95; CI: 1.76-2.15), and very preterm (RR: 3.45; CI: 2.95-4.04) than term. This relationship was maintained for most organ systems and malformation types evaluated when checked individually. Being born with more than one CM increased the likelihood of being born PT (OR: 1.72; CI: 1.37-2.15).

CONCLUSIONS

Congenital malformations in children have a significant impact upon the likelihood of being born PT, and contribute significantly to the degree of prematurity.

Descriptive epidemiology of selected birth defects, areas of Lombardy, Italy, 1999

BACKGROUND

Birth defects are a leading cause of neonatal and infant mortality in Italy, however little is known of the etiology of most defects. Improvements in diagnosis have revealed increasing numbers of clinically insignificant defects, while improvements in treatment have increased the survival of those with more serious and complex defects. For etiological studies, prevention, and management, it is important to have population-based monitoring which provides reliable data on the prevalence at birth of such defects.

METHODS

We recently initiated population-based birth defect monitoring in the Provinces of Mantova, Sondrio and Varese of the Region of Lombardy, northern Italy, and report data for the first year of operation (1999). The registry uses all-electronic source files (hospital discharge files, death certificates, regional health files, and pathology reports) and a proven case-generation methodology, which is described. The data were checked manually by consulting clinical records in hospitals. Completeness was checked against birth certificates by capture-recapture. Data on cases were coded according to the four-digit malformation codes of the International Classification of Diseases, Ninth Revision (ICD-9). We present data only on selected defects.

RESULTS

We found 246 selected birth defects in 12,008 live births in 1999, 148 among boys and 98 among girls. Congenital heart defects (particularly septal defects) were the most common (90.8/10,000), followed by defects of the genitourinary tract (34.1/10, 000) (particularly hypospadias in boys), digestive system (23.3/10,000) and central nervous system (14.9/10,000), orofacial clefts (10.8/10,000) and Down syndrome (8.3/10,000). Completeness was satisfactory: analysis of birth certificates resulted in the addition of two birth defect cases to the registry.

CONCLUSION

This is the first population-based analysis on selected major birth defects in the Region. The high birth prevalences for septal heart defect and hypospadias are probably due to the inclusion of minor defects and lack of coding standardization; the latter problem also seems important for other defects. However the data produced are useful for estimating the demands made on the health system by babies with birth defects.

Maternal and perinatal characteristics in relation to neuroblastoma

BACKGROUND

Neuroblastoma is the most common malignancy among infants, but risk factors remain poorly understood. Because most patients present in the first few years of life, it has been hypothesized that prenatal and perinatal exposures may contribute to the pathogenesis of neuroblastoma.

METHODS

A population-based case-control study was conducted by using linked birth and cancer registry records from 1980 to 2004 in Washington State. Maternal and infant characteristics from birth and hospital discharge records for 240 cases of neuroblastoma and 2400 controls were compared.

RESULTS

Neuroblastoma was associated with the presence of major congenital abnormalities (odds ratio [OR], 6.86; [95% CI], 2.92-16.08), particularly with cardiac abnormalities (OR, 5.84; 95% CI, 1.93-17.66), even after excluding abnormalities near the primary tumor. A borderline association was observed with maternal gestational diabetes (OR, 1.84; 95% CI, 0.98-3.47). The magnitude of both associations was greater when the analysis was limited to children who were diagnosed at age <1 year.

CONCLUSIONS

The findings from this population-based study supported prior case-control studies that identified an etiologic link between neuroblastoma and congenital abnormalities. However, to the authors' knowledge, the association between neuroblastoma and maternal diabetes has not been reported previously and requires further study.

The reliability and validity of birth certificates

OBJECTIVES

To summarize the reliability and validity of birth certificate variables and encourage nurses to spearhead data improvement.

DATA SOURCES

A Medline key word search of reliability and validity of birth certificate, and a reference review of more than 60 articles were done.

STUDY SELECTION

Twenty-four primary research studies of U.S. birth certificates that involved validity or reliability assessment.

DATA EXTRACTION

Studies were reviewed, critiqued, and organized as either a reliability or a validity study and then grouped by birth certificate variable.

DATA SYNTHESIS

The reliability and validity of birth certificate data vary considerably by item. Insurance, birthweight, Apgar score, and delivery method are more reliable than prenatal visits, care, and maternal complications. Tobacco and alcohol use, obstetric procedures, and delivery events are unreliable. Birth certificates are not valid sources of information on tobacco and alcohol use, prenatal care, maternal risk, pregnancy complications, labor, and delivery.

CONCLUSIONS

Birth certificates are a key data source for identifying causes of increasing U.S. infant mortality but have serious reliability and validity problems. Nurses are with mothers and infants at birth, so they are in a unique position to improve data quality and spread the word about the importance of reliable and valid data. Recommendations to improve data are presented.

Problems in using birth certificate files in the capture-recapture model to estimate the completeness of case ascertainment in a population-based birth defects registry in New York State

BACKGROUND

The limitations and underlying assumptions of the capture-recapture methods have hindered their application in epidemiological settings, especially in evaluating the completeness of birth defects registries. This study explored the possibility of using birth certificates as the secondary data source in a simple two-source capture-recapture model to estimate the completeness of case ascertainment of the Congenital Malformations Registry (CMR) for selected major birth defects.

METHODS

The CMR and the birth certificates were used as the primary and secondary sources, respectively. Children who were born in 1996-2001 and had selected major birth defects were identified from the two sources. The accuracy of the diagnoses was examined by comparing the individual birth defect categories of the children from the two sources.

RESULTS

Discrepancies in birth defect categories in the two data sources and false positives in the birth certificates were the major problems encountered in estimating the completeness of the CMR using the simple two-source capture-recapture method. The estimated completeness for selected major birth defects was only about 71%. Stratified analyses resulted in relatively high estimated completeness for oral clefts (90%) and Down syndrome (88%). CONCLUSIONS Although the birth certificate data was not a good source for estimating the completeness of case ascertainment of the CMR using capture-recapture methods, the analyses provided reasonable estimates for some conditions that were relatively easy to identify and diagnose at birth, such as oral clefts and Down syndrome.

The epidemiology of extrahepatic biliary atresia in New York State, 1983-98

The aetiology of biliary atresia, the leading cause of neonatal extrahepatic jaundice and the main indication for liver transplantation in children, is unknown. Recent research has focused on an infectious aetiology and the development of viral models in animals. The few published epidemiological studies report conflicting results for seasonal, geographical, and racial variations in incidence. In this study, New York State (NYS) Congenital Malformations Registry data from 1983 to 1998 were compared with resident live birth certificate data. County of residence, birth date, gestational age, birthweight, gender, maternal race and maternal age were extracted from the birth certificate data. Isolated and sequence cases were combined for analysis. Observed and expected numbers of cases were calculated by NYS region. Overall, 369 biliary atresia cases were reported in the 16-year study period, a rate of 0.85 [95% CI 0.76, 0.93] per 10,000 live births. Of these, 249 isolated/sequence cases were ascertained, a rate of 0.57 [95% CI 0.50, 0.64] per 10,000 live births. The rate ratio of biliary atresia in New York City (NYC) compared with other NYS was 2.19 [95% CI 1.69, 2.84]. Seasonal patterns varied by region with spring births at highest risk in NYC and September to November births at highest risk in other NYS. The rate ratio in black vs. white mothers was 1.94 [95% CI 1.48, 2.54]. Birthweight and gestational age were associated with biliary atresia with preterm low-birthweight infants at highest risk [RR 3.24, 95% CI 2.20, 4.76]. The association of isolated/sequence biliary atresia with season, preterm birth, and low birthweight in our study supports an infectious disease hypothesis.

Birth certificate methods in five hospitals

This study evaluated the methods of data collection of birth certificate information by five high-delivery hospitals in northern Texas. Research purposes were to identify sources and methods of birth certificate data collection and identify the most-reliable methods. This descriptive study involved interviews of each hospital's data collectors and review of 1999 Texas birth certificate data. Medical record clerks, whose training varied, but usually consisted of orientation by another medical record clerk, collected birth certificate data within 24 hours of birth. There was no standard method for training, nor was there a minimum level of education required. In four of the five hospitals studied, a birth certificate clerk collected most of the information with limited input from other medical sources. The information obtained on birth certificates therefore varied according to the collector and the priority placed upon the accuracy of information. Birth certificate data contain questionable reliability, which undermines data use in research, funding, and policy decisions.

Maternal smoking and birth defects: validity of birth certificate data for effect estimation

OBJECTIVES

The authors sought to assess the validity of birth certificate data for estimating the association between maternal smoking and birth defects. The US standard birth certificate includes check boxes for maternal smoking and for 21 congenital anomalies. The sensitivity and specificity of birth certificate data have been studied, but previous studies have not addressed the validity of these data for estimating the association between birth defects and maternal smoking or other risk factors.

METHODS

US public-use natality data (1997-1998) were used to calculate the prevalence ratio (adjusted for maternal age, race/ethnicity, and education) for the association between maternal smoking and 13 defects/defect categories. All analyses were restricted to 45 states, New York City, and the District of Columbia because they collect both maternal smoking and birth defect data.

RESULTS

Maternal smoking was associated with an increased prevalence of hydrocephaly (adjusted prevalence ratio [PR] = 1.24; 95% confidence interval [CI] = 1.08, 1.43), microcephaly (PR 1.47; 95% CI 1.15, 1.88), omphalocele/gastroschisis (PR 1.37; 95% CI 1.22, 1.53), cleft lip/palate (PR 1.35; 95% CI 1.25, 1.45), clubfoot (PR 1.62; 95% CI 1.49, 1.75), and polydactyly/syndactyly/adactyly (PR 1.33; 95% CI 1.23, 1.43 ). Previous studies have indicated an association between maternal smoking and gastroschisis, oral clefts, and clubfoot with effect estimates of similar magnitude to this study.

CONCLUSIONS

These findings suggest that birth certificate data may be useful for exploratory or corroborative studies estimating the association between birth defects and some risk factors recorded on birth certificates.

Data quality and the spatial analysis of disease rates: congenital malformations in New York State

Spatial analyses of disease rates are increasing as the hardware and software used in disease surveillance and cluster investigations become more accessible and easier to use. The results of these analyses should be interpreted with caution since inconsistencies in health outcome reporting and population estimates may lead to erroneous conclusions. In this report we provide an example, using data on congenital malformations in New York State, to show how under-reporting of malformations by some New York City hospitals can lead to apparent clusters of malformations in other areas of the state where reporting is more complete. We illustrate how spatial analysis techniques can be used to locate under-reporting problems and determine the extent to which the problem exists.

Birth defects surveillance: assessing the "gold standard"

OBJECTIVES

This study assessed the sensitivity of the Metropolitan Atlanta Congenital Defects Program (MACDP) by capitalizing on the delayed receipt of a data source.

METHODS

In 1997, we reviewed the medical records of potential cases from the 1995 birth certificates that had not previously been identified by the MACDP. Capture-recapture methods produced an estimate of total cases.

RESULTS

We identified 1149 infants with defects, including 20 exclusively from birth certificates. The estimated sensitivity of the MACDP when data from birth certificates were included was 86.9% (95% confidence interval [CI] = 80.6%, 91.9%) at 1 year after birth, increasing to 94.8% (95% CI = 90.3%, 97.8%) at 2 years after birth.

CONCLUSIONS

The MACDP underestimates defects by 13% at 1 year after birth and by 5% at 2 years after birth.

Epidemiology of holoprosencephaly and phenotypic characteristics of affected children: New York State, 1984-1989

Holoprosencephaly is a congenital defect of the median structures of the brain and face. The epidemiology is poorly known due to the paucity of population-based studies. This study describes the epidemiology of holoprosencephaly in a large population, using cases identified through the New York State Congenital Malformations Registry, and born in 1984-1989. We describe the craniofacial abnormalities present, their frequency, and their cooccurrence, and we examine the correspondence between the severity of craniofacial abnormalities, chromosomal abnormalities, and severity of the brain defect. Liveborn cases totaled 78, yielding a prevalence of 4.8 per 100,000 live births. Prevalence among girls was nearly double that in boys, and was 4.2 times higher among infants of mothers under age 18 compared to infants of older mothers. Only 9.8% of all cases had no craniofacial abnormalities other than the brain defect. Eye malformations were present in 76.8%, nose malformations in 69.5%, ear malformations in 50%, and oral clefts in 41.5%. These malformations arise at different times during gestation. The variability in patterns of cooccurrence suggests variability in the developmental pathways and/or timing of developmental derangements which result in holoprosencephaly. This, in turn, is consistent with a model of multiple causes. Children with alobar holoprosencephaly tended to have the most severe craniofacial anomalies, but the correspondence was not 100%. Craniofacial phenotype does not consistently discriminate between cytogenetically normal and abnormal cases.

First year-of-life mortality among infants with oral clefts: New York State, 1983-1990

This study examined the mortality experience of children with oral clefts using the New York State Congenital Malformations Registry. Infants born in the years 1983 to 1990 to New York residents, diagnosed with an oral cleft and matched to their birth certificate were included in the analysis. Children with oral clefts were compared to a sample of live births from the years 1983 to 1990 without malformations. Children with cleft palate without additional malformations had a statistically nonsignificant adjusted risk of 1.2 when compared to children with no malformations. Children with cleft lip with or without cleft palate had a 1.1 adjusted risk. However, 35% of children with oral clefts had associated malformations and experienced much higher mortality. Children with oral clefts should be carefully evaluated for additional malformations; if none are found, their mortality appears not to be elevated.