The surveillance of birth defects: the usefulness of the revised US standard birth certificate

Risk factors for antepartum and intrapartum stillbirth: a population-based study

To examine disparities in risk factors for stillbirths and its occurrence in the antepartum versus intrapartum periods. A population-based, cross-sectional study using data on women that delivered singleton births between 20 and 43 weeks in Missouri (1989-1997) was conducted (n = 626,883). Hazard ratios and 95% confidence intervals were derived from regression models and population attributable fractions were estimated to examine the impact of risk factors on stillbirth. Among African Americans, risks of antepartum and intrapartum stillbirth were 5.6 and 1.1 per 1,000 singleton births, respectively; risks among whites were 3.4 and 0.5 per 1,000 births, respectively. Maternal age > or = 35 years, lack of prenatal care, prepregnancy body mass index (BMI) > or = 30 kg/m2, and prior preterm or small-for-gestational age birth were significantly associated with increased risk for antepartum stillbirth among whites, but not African Americans. BMI < or = 18.5 kg/m2 was associated with antepartum and intrapartum stillbirth among African Americans, but not whites. The presence of any congenital anomaly, abruption, and cord complications were associated with antepartum stillbirth in both races. Premature rupture of membranes was associated with intrapartum stillbirth among whites and African Americans, but intrapartum fever was associated with intrapartum stillbirth among African Americans. These risk factors were implicated in 54.9% and 19.7% of antepartum and intrapartum stillbirths, respectively, among African American women, and in a respective 46.6% and 11.9% among white women. Considerable heterogeneity in risk factors between antepartum and intrapartum stillbirths is evident. Knowledge on timing of stillbirth specific risk factors may help clinicians in decreasing antepartum and intrapartum stillbirth risks through monitoring and timely intervention.

Measuring the quality of inpatient obstetrical care

Obstetric admissions are the leading cause of hospitalization for women in the United States, accounting for over 4 million hospital discharges each year. Measuring the quality of inpatient obstetrical care provided to these women is becoming increasingly important to patients, providers, and insurers. While numerous quality measures have been proposed, there is no agreement as to which measures should be used. An ideal quality measure for inpatient obstetrics would encompass 5 major characteristics: 1) association with meaningful maternal and neonatal outcomes, 2) relation to outcomes that are influenced by physician/health system behaviors, 3) affordability for application on a large scale basis, 4) acceptability to practicing obstetricians as a meaningful marker of quality, and 5) reliability/reproducibility. Traditional quality measurement tools such as maternal mortality, neonatal mortality and cesarean delivery rate are flawed measures. New measurements such as risk-adjusted primary cesarean rates, the nulliparous term singleton vertex cesarean birth (NTSV) rate, and the Adverse Outcomes Index (AOI) are currently being studied but these measures require further validation before widespread adoption.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to summarize that quality measures of inpatient obstetrical care are numerous, explain that no one agrees on which measures should be used, and state that newer measures, once validated, should be considered.

Accuracy of birth certificate and hospital discharge data: a certified nurse-midwife and physician comparison

OBJECTIVES

Birth certificate and hospital discharge data are relied upon heavily for national surveillance and research on maternal health. Despite the great importance of these data sources, the recording accuracy in these datasets, comparing birth attendant type, has not been evaluated. The study objective was to assess the variation in chart documentation accuracy between certified nurse-midwives (CNMs) and physicians (MDs) for selected maternal variables using birth certificate and hospital discharge data.

METHODS

Data was obtained on women delivering in 10 Washington State hospitals that had both CNM and MD-attended births in 2000 (n = 2699). Using the hospital medical record as the gold standard of accuracy, the true positive rate (TPR) for selected maternal medical conditions, pregnancy complications, and intrapartum and postpartum events was calculated for CNMs and MDs using birth certificate data, hospital discharge data, and both data sources combined.

RESULTS

The magnitude of TPRs for most recorded maternal medical conditions, pregnancy complications, and intrapatum and postpartum events was higher for CNMs than for MDs. TPRs were significantly higher in birth certificate records for pregnancy-induced hypertension, premature rupture of membranes, labor augmentation, induction of labor, and vaginal birth after cesarean (VBAC) for CNM-attended births relative to MDs. Among combined data sources, CNM TPRs were significantly higher for pregnancy-induced hypertension and premature rupture of membranes.

CONCLUSIONS

CNMs had consistently higher accuracy of recorded maternal medical conditions, pregnancy complications, and intrapartum and postpartum events when compared to MDs for all data sources, with several being statistically significant. Our findings highlight discrepancies between CNM and MD hospital chart documentation, and suggest that epidemiologic researchers consider the issue of measurement error and birth attendant type.

Reduction in orofacial clefts following folic acid fortification of the U.S. grain supply

BACKGROUND

Folic acid fortification in the United States became mandatory January 1, 1998, to reduce the occurrence of neural tube defects (NTDs). We evaluated the impact of folic acid fortification on orofacial clefts using United States birth certificate data for 45 states and the District of Columbia.

METHODS

Prevalence ratios (PRs) were calculated comparing orofacial cleft prevalence among births prefortification (1/1990-12/1996) and postfortification (10/1998-12/2002), based on fortification status at conception. The JoinPoint Regression Program and exponentially weighted moving average charts (EWMA) were used to assess the timing of any statistically significant changes in prevalence. Data were stratified by maternal race/ethnicity, age, smoking, and timing of prenatal care.

RESULTS

Orofacial clefts declined following folic acid fortification (PR=0.94; 95% CI: 0.92-0.96). The EWMA chart flagged a significant decrease in the fourth quarter of 1998. The JoinPoint graph had one change in slope, with a significant quarterly percent change (-0.34) between 1996 and 2002. The decline in orofacial clefts occurred in non-Hispanic Whites but not other racial/ethnic groups, nonsmokers but not women who reported smoking during pregnancy, and women who received prenatal care in the first trimester but not women who began receiving care later in pregnancy.

CONCLUSION

Folic acid fortification in the United States was associated with a small decrease in orofacial cleft prevalence, with the timing of the decline consistent with the introduction of fortification. The decline is much smaller than that observed for NTDs, but nonetheless suggests an additional benefit of this public health intervention.

Back to the future? A critical commentary on the 2003 U.S. National standard certificate of live birth

Vital statistics documents for the United States have been revised approximately decennially throughout the past century. In this commentary we review the contents of the 2003 revision of the national standard certificate of live birth, focusing on changes from the certificates in use nationally since 1989, and identifying strengths and weaknesses of key data elements. Additional federal-state partnership funding is imperative to support the transition to the new standard certificates, and to ensure a focus on data quality at the state and national levels.

Impact of anomalous triplets on morbidity outcomes of normal in utero siblings

OBJECTIVE

To evaluate the impact of number of anomalous fetuses on the prevalence of very preterm births (< 32 weeks), very low birth weight (< 1,500 g), and small for gestational age (SGA) infants among their normal cotriplets.

METHODS

Cross-sectional study of United States triplet births from 1995 to 2000 using Matched Multiple Birth Files, comparing outcomes for triplet sets with no anomalous, 1 anomalous, and 2 anomalous fetuses. Chi-square test for trend and multiple logistic regression analyses, applying generalized estimating equations to account for correlation among cotriplets, were implemented.

RESULTS

Of 34,881 matched triplets, 34,104 (97.8%) were nonanomalous (2.2% prevalence of fetal anomaly). Prevalence of very preterm birth (P < .001) and very low birth weight (P < .001), but not SGA (P = .52), among nonanomalous births increased significantly with number of anomalous cotriplets. The prevalence of very preterm birth was 44.1%, 54.8%, and 68.8%, respectively, as number of anomalous triplets per set increased from none to two. The prevalence of very low birth weight was 32.3%, 39.6%, and 62.0%, respectively. These trends remained unchanged after adjustment for correlation and potential confounding.

CONCLUSION

Prevalence of triplet births with gestation less than 32 weeks and birth weight less than 1,500 g, but not SGA, among nonanomalous triplets increase linearly with number of anomalous members within triplet sets.

LEVEL OF EVIDENCE

III.

Validade das informações das declarações de nascidos vivos com base em estudo de caso-controle

A pesquisa Mortalidade Perinatal na Região Sul do Município de São Paulo: Um Estudo Caso-controle de Base Populacional possibilitou a comparação das informações das declarações de nascido vivo (DN) com as obtidas em entrevistas com as mães e o registro nos prontuários hospitalares, e permitiu avaliar diferenças de registro nos nascimentos que resultaram em óbitos neonatais precoces (casos) e sobreviventes (controles). Para avaliar a confiabilidade e validade das informações das DN foram utilizadas medidas de concordância, sensibilidade, especificidade, prevalências real e estimada. A paridade materna e presença de anomalias congênitas mostraram elevada ausência de registro. O peso ao nascer e o tipo de parto são bem identificadas pela DN, em casos e controles. A DN mostrou alta sensibilidade e especificidade para captar os nascimentos de pré-termo nos casos, contudo, subestima o número de nascimentos de pré-termo: 30,8% nos controles e 2,9% nos casos. O SINASC superestima em cerca de duas vezes a presença de nascimentos de mães de baixa escolaridade. Verificou-se que as DNs dos controles têm informações mais completas, porém a informação registrada para os casos apresenta melhor qualidade.

Survival of infants with neural tube defects in the presence of folic acid fortification

OBJECTIVE

Neural tube defects (NTDs) are preventable through preconceptional and periconceptional folic acid intake. Although decreases in the prevalence of NTDs have been reported since folic acid fortification of United States grain products began, it is not known whether folic acid plays a role in reducing the severity of occurring NTDs. Our aim was to determine whether survival among infants born with spina bifida and encephalocele has improved since folic acid fortification and to measure the effects of selected maternal, pregnancy, and birth characteristics on first-year (infant) survival rates.

METHODS

A retrospective cohort study was conducted and included 2841 infants with spina bifida and 638 infants with encephalocele who were born between 1995 and 2001 and were registered in any of 16 participating birth defects monitoring programs in the United States. First-year survival rates for both spina bifida and encephalocele cohorts were measured with Kaplan-Meier estimation; factors associated with improved chances of first-year survival, including birth before or during folic acid fortification, were measured with Cox proportional-hazards regression analysis.

RESULTS

Infants with spina bifida experienced a significantly improved first-year survival rate of 92.1% (adjusted hazard ratio: 0.68; 95% confidence interval: 0.50-0.91) during the period of mandatory folic acid fortification, compared with a 90.3% survival rate for those born before fortification. Infants with encephalocele had a statistically nonsignificant increase in survival rates, ie, 79.1% (adjusted hazard ratio: 0.76; 95% confidence interval: 0.51-1.13) with folic acid fortification, compared with 75.7% for earlier births.

CONCLUSIONS

Folic acid may play a role in reducing the severity of NTDs in addition to preventing the occurrence of NTDs. This phenomenon contributes to our understanding of the efficacy of folic acid. Additionally, as survival of NTD-affected infants improves, health care, education, and family support must expand to meet their needs.

Evaluation of the Texas Birth Defects Registry: An active surveillance system

BACKGROUND

Evaluations of surveillance systems are necessary to determine if the goals of the system are being met, how efficiently the surveillance is being implemented, and if resources are being used appropriately. An evaluation of the Texas Birth Defects Registry was conducted to assess the overall quality of data collection and to examine variations across regions of the state.

METHODS

The registry was evaluated by using published guidelines for evaluating public health surveillance systems; the evaluation included staff interviews, process observation, and secondary data analysis.

RESULTS

The registry monitors >370,000 births/year through active surveillance, with considerable disparities in workload across regions of the state. Because of the geographic size and substantial population of Texas, data collection is complex. However, the estimated sensitivity of the system appears sufficient, and rates for selected defects are highly comparable with other U.S. active birth-defect surveillance systems. Registry staff continually monitor the quality of data collection and provide additional training. Amid unstable funding, the registry staff have demonstrated optimal foresight and flexibility to adapt and continue quality data collection. Timeliness needs to be improved and more consistent quality assurance is needed across regions of the state. Retaining staff and increasing visibility are essential to providing more stability.

CONCLUSIONS

Active surveillance for birth defects is labor-intensive but provides invaluable data for its stakeholders. The Texas Birth Defects Registry has proven to be a quality surveillance system and a beneficial resource for Texas.

Feasibility of using the national hospital discharge survey to estimate the prevalence of selected birth defects

BACKGROUND

Nationally representative data on the prevalence of certain birth defects are largely unavailable. We evaluated the feasibility of using data from the National Hospital Discharge Survey (NHDS) to describe the prevalence of selected birth defects.

METHODS

All live births recorded in the NHDS during 1999-2001 were included. The prevalence for selected birth defects was calculated using weighted ratio estimators. Prevalence ratios comparing the NHDS estimates to published national estimates from the National Birth Defects Prevention Network (NBDPN) were calculated.

RESULTS

With the exception of common truncus, the NHDS prevalence for the selected defects was consistently lower than the NBDPN estimates. The prevalence ratios ranged from 0.38 for trisomy 18 and anopthalmia/micropthalmia to 1.16 for common truncus. The NHDS prevalence estimates for spina bifida without anencephaly (PR 0.89, 95% CI: 0.57-1.22) and gastroschisis/omphalocele (PR 0.94, 95% CF: 0.48-1.40) most closely approximated the NBDPN estimates.

CONCLUSIONS

NHDS data underestimate the prevalence of most birth defects. Additional research is needed to determine whether NHDS estimates may be useful for evaluating trends in certain conditions. Surveillance systems employing active case-finding continue to provide more accurate estimates of birth defects prevalence.

Validity of hospital discharge data for identifying infants with cardiac defects

OBJECTIVE

To examine validity of the International Classification of Diseases, 9th Edition, Clinical Modification (ICD-9-CM) codes in discharge data for identifying infants with cardiac defects according to surveillance guidelines.

STUDY DESIGN

Retrospective medical record review of infants born in 2001 at one hospital in Minneapolis, Minnesota. Infants were identified using ICD-9-CM codes from hospital discharge data, and keywords in medical records.

RESULTS

Of 2,697 children, ICD-9-CM codes identified 66 infants coded with cardiac defects; physician review confirmed 24 had cardiac defects. Only 35 of 85 (41.2%) ICD-9-CM codes accurately reflected the cardiac defect diagnoses. Additional case finding located four infants with five cardiac defects. Sensitivity of ICD-9-CM codes for identifying these infants was 0.857, predictive value positive was 0.364.

CONCLUSIONS

ICD-9-CM codes from hospital discharge data identified most infants with cardiac defects, but many were false positives. ICD-9-CM codes were inaccurate for specific cardiac defects.

Clustering of U.S. women receiving no prenatal care: differences in pregnancy outcomes and implications for targeting interventions

OBJECTIVES

Prenatal care is an established mechanism for identifying and managing risk factors impacting pregnancy outcomes. Despite aggressive efforts in the United States (US) to assure that all women begin care in the first trimester, every year about 70,000 women in the US receive no care prior to delivery. We hypothesized that US women receiving no prenatal care comprise clusters (subgroups) with distinctive behavioral, socio-demographic, and medical risks and that birth outcomes differ among the clusters.

METHODS

White, Black, and Hispanic women (n = 126,220) receiving no prenatal care and delivering a live, singleton infant were identified from linked birth and death certificates for years 1995 through 1997. Cluster analysis was used to group women with similar characteristics, and cluster assignment was evaluated using discriminant analysis. Birth outcomes for any care and no-care women were then examined using logistic regression.

RESULTS

Six replicable clusters of women with no care were identified. Birth outcomes varied significantly among clusters and were two to four times worse for no-care clusters compared to outcomes for women receiving any care.

CONCLUSIONS

Cluster analysis is an effective alternative for grouping individuals for use in public health education, intervention, and outreach programming. Women receiving no prenatal care were characteristically different from women receiving any care in this study, but they did not represent a homogenous group. Findings suggest that interventions should target reducing the proportion of women receiving no care and should be tailored to specific no-care clusters.

Fetal deaths in the United States, 1997 vs 1991

OBJECTIVE

The purpose of this study was to examine the temporal change in fetal death risk in the US from 1991 to 1997, and to assess the extent to which changes in registration practices and labor induction have contributed to that change.

STUDY DESIGN

This was a cohort study of all singleton pregnancies 20 to 43 weeks of gestation in 1991 and 1997 in the US.

RESULTS

From 1991 to 1997, the overall fetal death rate fell from 77.6 to 67.8 per 10,000 total births. However, fetal deaths at 20 to 22 weeks as a proportion of total births increased from 14.5 to 16.9 per 10,000. In a Cox regression analysis, the crude period effect (1997 vs 1991) at 40 to 43 weeks was 0.87 (95% CI 0.80-0.94), and remained virtually unchanged (HR 0.88, 95% CI 0.81-0.96) after adjustment for maternal sociodemographic, medical, and lifestyle risk factors. In ecologic (Poisson regression) analysis based on states as the unit of analysis, the crude period effect in non-Hispanic whites (RR 0.79, 95% CI 0.74-0.84) disappeared (RR 0.98, 95% CI 0.82-1.16) after adjusting for induction of labor. The effect of induction in blacks was limited to 42 to 43 weeks in those at high risk.

CONCLUSION

Increased registration is probably responsible for an increase in fetal death risk at 20 to 22 weeks of gestation, whereas the increasing trend toward routine labor induction at and after term appears to have reduced the risk of fetal death, especially among whites.

Reliability of Indiana birth certificate data compared to medical records

PURPOSE

The purpose of this study was to measure the reliability of data reported on Indiana electronic birth certificates. Knowing the accuracy of birth certificate data is crucial when identifying community health needs and evaluating birth outcomes interventions.

METHODS

This study compared 1996 electronic birth certificate data on a random sample of 1050 Indiana hospital births to data abstracted from the hospital medical records for the same patients. Kappa scores, Pearson r correlation values, sensitivity, specificity, and positive predictive values of the birth certificate data were used to measure agreement.

RESULTS

Parents' demographic variables had the best agreement, followed by birth outcome variables. Delivery type, cesarean indications, pregnancy history, prenatal care and mother's risk variables were found to have moderate agreement. Agreement was poor for variables measuring labor and delivery complications, obstetric procedures, concurrent illnesses, pregnancy complications, congenital anomalies, and abnormal conditions.

CONCLUSIONS

The results of this study clearly show that some important descriptive and outcome data are reliable while infrequent events are generally not. The results indicate a need to improve the quality of data reported on birth certificates.

Down syndrome births in the United States from 1989 to 2001

OBJECTIVE

We investigated the observed and expected Down syndrome livebirths in the US from 1989 to 2001.

STUDY DESIGN

Using birth certificate data, we recorded maternal age-specific live births from 1989 to 2001, and stratified them by women 15 to 34 and 35 to 49 years old. We estimated Down syndrome live births from 1989 to 2001, assuming no terminations. We recorded Down syndrome live births by year from 1989 to 2001.

RESULTS

Despite an expected 1.32-fold increase in Down syndrome live birth rates from 1989 to 2001, Down syndrome live births actually declined. In 1989, the rate of Down syndrome cases was 15% lower than expected, decreasing to 51% by 1998. Women 15 to 34 had 45% fewer affected pregnancies in 2001, while women 35 to 49 had 53% fewer in 2001. We estimated that Down syndrome live births decreased from 3962 in 1989 to 3654 in 2001.

CONCLUSION

Down syndrome live births declined in the US despite an expected increase caused by delayed or extended childbearing.

Low maternal age and neonatal survival of extremely preterm twins (20-28 weeks of gestation)

OBJECTIVE

We investigated the relationship between low maternal age and neonatal survival among extremely preterm twins.

METHODS

This was a retrospective cohort study on live births of extremely preterm twins delivered to teenaged mothers (aged 15-19 years) in the United States within the period 1995 through 1998. Overall neonatal and early and late neonatal mortality in this category was compared with that of a similar group of twins born to young adult mothers (aged 20-29 years). We used the generalized estimating equation framework in computing relative risks after adjusting for intracluster correlations.

RESULTS

Analysis involved 2,290 extremely preterm liveborn twins of teenaged mothers and 8,709 born to young adult mothers. Overall, neonatal mortality was 29% higher among the extremely preterm twins born to teenaged mothers (adjusted odds ratio [OR] 1.29; 95% confidence interval [CI] 1.04%, 1.59%). The disparity in neonatal survival was chiefly in the early neonatal period (adjusted OR 1.34; 95% CI 1.07%, 1.67%), while late neonatal mortality was comparable (adjusted OR 0.91; 95% CI 0.58%, 1.42%). In addition, twins of teenaged mothers had significantly higher level of mortality, except for the birth weight category of 1,000-1,499 g.

CONCLUSION

Low maternal age was found to be associated with elevated risk of neonatal death among extremely preterm twins. The preponderance of deaths among extremely preterm twins of teenaged mothers in the early neonatal period appeared to be responsible for the disparity in survival. This information may be useful for targeted interventions aimed at enhancing survival of extremely preterm twins born to teenagers, as well as for instituting optimal management options in the clinical setting.

LEVEL OF EVIDENCE

II-2

Random error and undercounting in birth defects surveillance data: implications for inference

BACKGROUND

There has been an ongoing debate among birth defects investigators about whether or not to publish estimates of rates of birth defects with confidence intervals to allow for comparisons of rates across regions and time. A major impediment in resolving this debate has been the lack of a framework for quantifying uncertainties in the data that can be applied uniformly to birth defects surveillance programs. This report presents an overview of random error and ascertainment bias in birth defects surveillance data, and of the implications of these errors for estimation and comparisons of birth defects rates.

METHODS

We consider when confidence intervals can be used as part of a strategy to make inference on rates, as well as ratios of or differences between two rates. Worth noting is that confidence intervals only address random error in the data. In the presence of undercounting of cases, estimation of rates and confidence intervals requires knowledge or an estimate of the extent of underascertainment. Rate estimates and confidence intervals that ignore such bias can be misleading. However, if it is reasonable to assume that the ascertainment bias is constant over time (or across regions), then it is possible to make valid comparisons of rates over time (or across regions) using ratio or difference estimators, even when lack of knowledge of the extent of undercounting makes estimating the absolute rate and its confidence interval problematic. Finally, sensitivity analyses can use confidence limits to determine the difference in ascertainment bias necessary to explain an apparent difference in rates.

CONCLUSION

Because birth defects surveillance systems have evolved in the absence of agreed upon standards to guide the process, it is difficult to determine the extent to which the variability in rates of birth defects across programs or over time is real or due to differences in surveillance methods. Efforts to develop standards for birth defects surveillance may help to minimize the variability in prevalence of birth defects due to differences in case ascertainment methods and allow for evaluations of real temporal and spatial variations in environmental effects. In the meantime, if comparisons of rates need to be made to address public health concerns, it would be prudent to conduct only such comparisons between regions or across time when the degree of case ascertainment can be assumed to be relatively constant across regions and time.

Impact of folic acid fortification in the United States: markedly diminished high maternal serum alpha-fetoprotein values

OBJECTIVE

Folic acid fortification of breads and grains was implemented in the United States in 1998 in an attempt to reduce the incidence of neural tube defects. Outcome data from birth registries have shown a 20% drop-less than originally predicted. In this study, we ascertain if the impact of folic acid fortification is better seen at the time of midtrimester prenatal diagnosis by looking at incidence of high maternal serum alpha-fetoprotein (MSAFP) values.

METHODS

Data regarding MSAFP levels in 61,119 patients undergoing maternal serum screening at a large commercial laboratory were categorized by multiples of the median (MoM). The data were compared between 2 groups: before mandatory supplementation in the United States in 1997 and after mandatory supplementation in 2000. High MSAFP values were further categorized as high (2.75-4.00 MoM) or very high (more than 4.00 MoM). Data were analyzed by chi(2) analysis.

RESULTS

Comparative data showed a 32% decrease of patients with MoM greater than 2.75 + (2.5% -1.7%). Further categorizations revealed similar decreases.

CONCLUSION

The introduction of folic acid fortification has produced a profound decrease in the number of high MSAFP values, reflective of a decreased incidence of neural tube defects. Our results help to validate the decision to fortify food with folic acid, which represents a highly successful public health policy for primary prevention of birth defects.

LEVEL OF EVIDENCE

II-2

Completeness of state administrative databases for surveillance of congenital heart disease

BACKGROUND

Tracking birth prevalence of cardiac defects is essential to determining time and space clusters, and identifying potential associated factors. Resource limitations on state birth defects surveillance programs sometimes require that databases already available be used for ascertaining such defects. This study evaluated the data quality of state administrative databases for ascertaining congenital heart defects (CHD) and specific diagnoses of CHD.

METHODS

Children's Hospital of Wisconsin (CHW) medical records for infants born 1997-1999 and treated for CHD (n = 373) were abstracted and each case assigned CHD diagnoses based on definitive diagnostic reports (echocardiograms, catheterizations, surgical or autopsy reports). These data were linked to state birth and death records, and birth and postnatal (< 1 year of age) hospital discharge summaries at the Wisconsin Bureau of Health Information (WBHI). Presence of any code/checkbox indicating CHD (generic CHD) and exact matches to abstracted diagnoses were evaluated.

RESULTS

Fifty-eight percent of cases with generic CHD were identified by state databases. Postnatal hospital discharge summaries identified 48%, birth hospital discharge summaries 27%, birth certificates 9% and death records 4% of these cases. Exact matches were found for 52% of 633 specific diagnoses. Postnatal hospital discharge summaries provided most matches.

CONCLUSION

State databases identified 60% of generic CHD and exactly matched about half of specific CHD diagnoses. The postnatal hospital discharge summaries performed best in both in identifying generic CHD and matching specific CHD diagnoses. Vital records had limited value in ascertaining CHD.

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.

Birth malformations and other adverse perinatal outcomes in four U.S. Wheat-producing states

Chlorophenoxy herbicides are widely used in the United States and Western Europe for broadleaf weed control in grain farming and park maintenance. Most of the spring and durum wheat produced in the United States is grown in Minnesota, Montana, North Dakota, and South Dakota, with more than 85% of the acreage treated with chlorophenoxy herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA). Rates of adverse birth outcomes in rural, agricultural counties of these states during 1995-1997 were studied by comparing counties with a high proportion of wheat acreage and those with a lower proportion. Information routinely collected and made available by federal agencies was used for this ecologic study. Significant increases in birth malformations were observed for the circulatory/respiratory category for combined sexes [odds ratio (OR) = 1.65; 95% confidence interval (CI), 1.07-2.55]. A stronger effect was observed for the subcategory, which excluded heart malformations (OR = 2.03; 95% CI, 1.14-3.59). In addition, infants conceived during April-June--the time of herbicide application--had an increased chance of being diagnosed with circulatory/respiratory (excluding heart) malformations compared with births conceived during other months of the year (OR = 1.75; 95% CI, 1.09-2.80). Musculoskeletal/integumental anomalies increased for combined sexes in the high-wheat counties (OR = 1.50; 95% CI, 1.06-2.12). Infant death from congenital anomalies significantly increased in high-wheat counties for males (OR = 2.66; 95% CI, 1.52-4.65) but not for females (OR = 0.48; 95% CI, 0.20-1.15). These results are especially of concern because of widespread use of chlorophenoxy herbicides.

Risk factors for intrapair birth weight discordance in twins

OBJECTIVES

To determine the risk factors for birth weight discordance in twins.

METHODS

We used the United States (1995-97) Matched Multiple Birth File (n = 294 568) to assess the association between birth weight discordance and maternal sociodemographic, pregnancy and infant characteristics.

RESULTS

Eighty-four per cent of the twins were 0-19% discordant, 11.1% were 20-29% discordant, 3.4% were 30-39% discordant, and 1.8% were > or = 2 40% discordant. The risk factors for birth weight discordance for same-sex twins were eclampsia (odds ratio (OR) 1.39,95% confidence interval (CI) 1.20, 1.61), pre-eclampsia (OR 1.31, 95% CI 1.24, 1.38), pre-existing hypertension (OR 1.32, 95% CI 1.12, 1.56), diabetes (OR 1.13, 95% CI 1.04, 1.24) and certain congenital anomalies. For opposite-sex twins, the risk factors for birth weight discordance were pre-eclampsia (OR 1.17, 95% CI 1.09, 1.27), pre-existing hypertension (OR 1.59,95% CI 1.32, 1.91), and certain congenital anomalies. Also, smoking and increased maternal age were associated with birth weight discordance in both same-sex and opposite-sex twins.

CONCLUSIONS

Maternal hypertensive disorders, smoking and delayed childbearing were associated with intrapair birth weight discordance. The mechanisms of these associations deserve further investigation.

Neural tube defect-specific infant mortality in the United States

BACKGROUND

Significant resources have been devoted to decreasing the rate of neural tube defects (NTDs) in the United States. Both surveillance data and birth records have strengths and limitations for evaluating the outcomes of this resource allocation. Cause-specific infant mortality data can be used as one measure to support evaluation efforts.

METHODS

Using period linked birth/infant death data from the National Center for Health Statistics (NCHS), a retrospective analysis was performed to assess the NTD-specific IMR at the national, state, and regional level. NTD-specific IMRs for the United States were calculated from 1996 to 1998; stratified rates by race/ethnicity, maternal age, age at death, and gestational age and birthweight by type of NTD for the total US population were based on three-year aggregates (1996-98); state and regional rates were based on four-year aggregates (1995-98).

RESULTS

Annual US NTD-specific IMRs significantly decreased between 1996 and 1998. Black infants were significantly less likely to die from an NTD when compared to white infants, largely attributed to the high rate of NTD-specific deaths among white Hispanic infants. Infants born to women less than 20 years were more likely than infants born to women in other age groups to die from an NTD. Seventy-six percent of all NTD-specific deaths occurred in the first 23 hours of life. Seventy-four percent of NTD-specific infant deaths were low birthweight and 58 percent were preterm. The Midwest had the highest rate of NTD-specific infant deaths among US regions.

CONCLUSION

Enhanced prevention efforts are needed to address the disparities in infant deaths due to NTDs between Hispanics and other populations, as well as women under 20 years. Decreases in NTD-specific IMRs may have been impacted by fortification of enriched grain products with folic acid since these efforts were optional beginning in 1996. While there are limitations in cause-specific IMRs, NTD-specific IMRs can be used as one measure to assess the impact of public health interventions aimed at reducing NTDs, respectful of the relatively small numbers.

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.

Reliability of birth certificate data: a multi-hospital comparison to medical records information

OBJECTIVE

To examine the reliability of birth certificate data and determine if reliability differs between teaching and nonteaching hospitals.

METHODS

We compared information from birth certificates and medical records in 33,616 women admitted for labor and delivery in 1993-95 to 20 hospitals in Northeast Ohio. Analyses determined the agreement for 36 common data elements, and the sensitivity, specificity, and positive and negative predictive values of birth certificate data, using medical record data as a "gold standard."

RESULTS

Sensitivity and positive predictive value varied widely (9-100% and 2-100%, respectively), as did agreement, which was "almost perfect" for measures of prior obstetrical history, delivery type, and infant Apgar score (K = 0.854-0.969) and "substantial" for several other variables (e.g., tobacco use (K = 0.766), gestational age (K = 0.726), prenatal care (K = 0.671)). However, agreement was only "slight" to "moderate" for most maternal risk factors and comorbidities (K = 0.085-0.545) and for several complications of pregnancy and/or labor and delivery (K = 0.285-0.734). Overall agreement was similar in teaching (mean K = 0.51) and nonteaching (K = 0.52) hospitals. Although agreement in teaching and nonteaching hospitals varied for some variables, no systematic differences were seen across types of variables.

CONCLUSIONS

Our findings indicate that the reliability of birth certificate data vary for specific elements. Researchers and health policymakers need to be cognizant of the potential limitations of specific data elements.

Talipes equinovarus and maternal smoking: a population-based case-control study in Washington state

BACKGROUND

Talipes equinovarus (TEV), also called congenital idiopathic clubfoot, true clubfoot and common clubfoot, is one of the most common major birth defects. Its correction is often difficult and expensive. Its etiology is poorly understood and few analytic epidemiological studies have been devoted to exploring specific risk factors for TEV.

METHODS

Our population-based study consists of 239 documented cases of idiopathic TEV obtained from hospital and outpatient sources and 365 controls identified via random digit dialing from five Western Washington counties. Structured maternal interviews were conducted by trained interviewers and multiple logistic regression used to evaluate associations between maternal smoking and birth of a child with TEV.

RESULTS

Our study shows strong associations between maternal smoking and idiopathic TEV. Case mothers were more likely to have smoked during pregnancy (OR = 2.2; 95% CI = 1.5, 3.3). Increased TEV risk was seen with increased smoking and estimates ranged from 1.5 for the lightest smokers to 3.9 for the heaviest smokers. Gender specific differences in risk were also noted with risk estimates of 1.8 (95% CI = 1.2, 3.0) for boys whose mothers smoked during pregnancy and 2.8 (95% CI = 1.4, 5.4) for girls. Trends for increased risk with higher numbers of cigarettes were noted for both genders. For isolated TEV, the overall odds ratio (OR) for smoking was 2.4 (95% CI = 1.6, 3.6) with a range from 1.4-4.6. No confounders were noted.

CONCLUSIONS

As postulated, maternal smoking during pregnancy appears to increase the risk of having a child with idiopathic clubfoot and the number of cigarettes smoked influence that risk. Further delineation of dose-response is warranted as are continued efforts to decrease maternal smoking during pregnancy.

Trends in neural tube defect prevalence, folic acid fortification, and vitamin supplement use

In this review, the authors analyze international trends in rates of neural tube defects (NTDs) during the past three decades. Population-based data sources include the Metropolitan Atlanta Congenital Defects Program and other US birth defects surveillance programs in the National Birth Defects Prevention Network, the International Clearinghouse for Birth Defects Monitoring Systems, and US and Canadian vital records. To analyze trends in vitamin consumption, we review data from the US National Health and Nutrition Examination Surveys and international surveys of multivitamin use. We discuss the role of factors associated with historic and continuing declines in NTD rates in most countries. These factors include the introduction and increased utilization of prenatal diagnosis, recommendations for multivitamin use in women of childbearing age, and population-wide increases in blood folate levels that have occurred since food fortification was mandated. We also discuss research needs for further NTD prevention. This is a US government work. There are no restrictions on its use.

Prevalence of spina bifida and anencephaly during the transition to mandatory folic acid fortification in the United States

BACKGROUND

In 1992, the United States Public Health Service recommended that all women of childbearing age consume 400 microg of folic acid daily. The Food and Drug Administration authorized the addition of synthetic folic acid to grain products in March 1996 with mandatory compliance by January 1998. The impact of these public health policies on the prevalence of neural tube defects needs to be evaluated. We sought to determine the prevalences of spina bifida and anencephaly during the transition to mandatory folic acid fortification.

METHODS

Twenty-four population-based surveillance systems were used to identify 5,630 cases of spina bifida and anencephaly from 1995-99. Cases were divided into three temporal categories depending on whether neural tube development occurred before folic acid fortification (January 1995 to December 1996), during optional fortification (January 1997 to September 1998), or during mandatory fortification (October 1998 to December 1999). Prevalences for each defect were calculated for each time period. Data were also stratified by programs that did and did not ascertain prenatally diagnosed cases.

RESULTS

The prevalence of spina bifida decreased 31% (prevalence ratio [PR] = 0.69, 95% confidence interval [CI] = 0.63-0.74) from the pre- to the mandatory fortification period and the prevalence of anencephaly decreased 16% (PR = 0.84, 95% CI = 0.75-0.95). Stratification by prenatal ascertainment did not alter results for spina bifida but did impact anencephaly trends.

CONCLUSIONS

The decline in the prevalence of spina bifida was temporally associated with folic acid fortification of US grain supplies. The temporal association between fortification and the prevalence of anencephaly is unclear.

Mortality in low birth weight infants according to level of neonatal care at hospital of birth

OBJECTIVE

In 1976, the Committee on Perinatal Health recommended that hospitals with no neonatal intensive care unit (NICU) or intermediate NICUs transfer high-risk mothers and infants that weigh <2000 g to a regional NICU. This standard was based on expert opinion and has not been validated carefully. This study evaluated the effect of NICU level and patient volume at the hospital of birth on neonatal mortality of infants with a birth weight (BW) of <2000 g.

METHODS

Birth certificates of 16 732 singleton infants who had a BW of <2000 g and were born in nonfederal hospitals in California in 1992 and 1993 were linked to death certificates and to discharge abstracts. The hospitals were classified by the level of NICU: no NICU, no intensive care; intermediate NICU, intermediate intensive care; community NICU, expanded intermediate intensive care; and regional NICU, tertiary intensive care. A logistic regression model that controlled for demographic risks, diagnoses, transfer, average NICU census, and NICU level was estimated using death within the first 28 days or first year of life if continuously hospitalized as the main outcome measure.

RESULTS

Compared with birth in a hospital with a regional NICU, risk-adjusted mortality of infants with BW of <2000 g was higher when birth occurred in hospitals with no NICU (odds ratio [OR]: 2.38; 95% confidence interval [CI]: 1.81-3.13), an intermediate NICU (OR: 1.92; 95% CI: 1.44-2.54), or a small (average census <15) community NICU (OR: 1.42; 95% CI: 1.14-1.76). Risk-adjusted mortality for infants who were born in hospitals with a large (average census > or =15) community NICU was not statistically different compared with those with a regional NICU (OR: 1.11; 95% CI: 0.87-1.43). Except for large community NICUs, all of these ORs are larger when the data are restricted to infants with BW of <1500 g or BW of <1250 g and smaller for BW between 1250 g and 1999 g and 1500 g and 1999 g. For large community NICUs, the results are similar for the smaller BW intervals and significant only for the larger BW interval.

CONCLUSIONS

These results support the recommendation that hospitals with no NICU or intermediate NICUs transfer high-risk mothers with estimated fetal weight of <2000 g to a regional NICU. For infants with BW of <2000 g, birth at a hospital with a regional NICU is associated with a lower risk-adjusted mortality than birth at a hospital with no NICU, intermediate NICU of any size, or small community NICU. Subsequent neonatal transfer to a regional NICU only marginally decreases the disadvantage of birth at these hospitals. The evidence for the few hospitals with large community NICUs is mixed. Although the data point to higher mortality in large community NICUs, they are not conclusive and additional study is needed on the mortality effects of large community NICUs. Greater efforts should be made to deliver infants with expected BW of <2000 g at hospitals with regional NICUs.

Drinking water contaminants and adverse pregnancy outcomes: a review

Concern for exposures to drinking water contaminants and their effects on adverse birth outcomes has prompted several studies evaluating chlorination disinfection by-products and chlorinated solvents. Some of these contaminants are found to be teratogenic in animal studies. This review evaluates 14 studies on chlorination disinfection by-products such as trihalomethanes (THMs) and five studies on chlorinated solvents such as trichloroethylene (TCE). The adverse birth outcomes discussed in this review include small for gestational age (SGA), low birth weight, preterm birth, birth defects, spontaneous abortions, and fetal deaths. Because of heterogeneities across the studies in the characterization of birth outcomes, the assessment and categorization of exposures, and the levels and mixtures of contaminants, a qualitative review was conducted. Generally, the chief bias in these studies was exposure misclassification that most likely underestimated the risk, as well as distorted exposure-response relationships. The general lack of confounding bias by risk factors resulted from these factors not being associated with drinking water exposures. The studies of THMs and adverse birth outcomes provide moderate evidence for associations with SGA, neural tube defects (NTDs), and spontaneous abortions. Because fewer studies have been conducted for the chlorinated solvents than for THMs, the evidence for associations is less clear. Nevertheless, the findings of excess NTDs, oral clefts, cardiac defects, and choanal atresia in studies that evaluated TCE-contaminated drinking water deserve follow-up.

Incomplete birth certificates: a risk marker for infant mortality

OBJECTIVES

This study assessed the relationship between incomplete birth certificates and infant mortality.

METHODS

Birth certificates from California (n = 538 945) were assessed in regard to underreporting of 13 predictors of perinatal outcomes and mortality.

RESULTS

Of the birth certificates studied, 7.25% were incomplete. Underreporting was most common in the case of women at high risk for poor perinatal outcomes and infants dying within the first day. Increasing numbers of unreported items were shown to be associated with corresponding increases in neonatal and postneonatal mortality rates.

CONCLUSIONS

Incomplete birth certificates provide an important marker for identifying high-risk women and vulnerable infants. Because data "cleaning" will result in the removal of mothers and infants at highest risk, birth certificate analyses should include incomplete records.

Validity of birth certificate data for the outcome of the previous pregnancy, Georgia, 1980-1995

The author evaluated the validity of four historically based variables collected on Georgia birth certificates: outcome of preceding pregnancy, history of delivery of a low- (<2,500 g) or high- (>4,000 g) birth-weight infant, and death of the baby resulting from the preceding pregnancy. Data were derived from birth and fetal death certificates that were linked for the first and second deliveries of 231,075 women in Georgia from 1980 through 1995. Deaths that occurred during the infant's first year of life were also linked to the birth certificate. For all but the survival variable, the outcome of the first birth as reported on the certificate for the second birth was compared with the outcome recorded on the certificate for the first birth, which was assumed to be correct. Except for ascertainment of death of the firstborn infant, sensitivities for the history of poor outcomes were low. Furthermore, sensitivities were higher when an extremely adverse outcome occurred in the first pregnancy or an adverse outcome recurred. The only high sensitivity was for past infant death (85.4%). These results suggest caution when using these variables to identify high-risk subsets for further research or control for confounding.

Public health 101 for informaticians

Abstract Public health is a complex discipline that has contributed substantially to improving the health of the population. Public health action involves a variety of interventions and methods, many of which are now taken for granted by the general public. The specific focus and nature of public health interventions continue to evolve, but the fundamental principles of public health remain stable. These principles include a focus on the health of the population rather than of individuals; an emphasis on disease prevention rather than treatment; a goal of intervention at all vulnerable points in the causal pathway of disease, injury, or disability; and operation in a governmental rather than a private context. Public health practice occurs at local, state, and federal levels and involves various professional disciplines. Public health principles and practice are illustrated by a case study example of neural tube defects and folic acid. The application of information science and technology in public health practice provides previously unfathomed opportunities to improve the health of the population. Clinical informaticians and others in the health care system are crucial partners in addressing the challenges and opportunities offered by public health informatics.

The completeness, validity, and timeliness of AIDS surveillance data

PURPOSE

To assess the completeness, validity, and timeliness of the AIDS surveillance system after the 1993 change in the surveillance case definition.

METHODS

To assess completeness of AIDS case reporting, three study sites conducted a comparison of their AIDS surveillance registries with an independent source of information. To evaluate validity, the same sites conducted record reviews on a sample of reported AIDS cases, we then compared agreement between the original report and the record review for sex, race, and mode of transmission. To evaluate timeliness, we calculated the median delay from time of diagnosis to case report, before and after the change in case definition, in each of the three study sites.

RESULTS

After expansion of the case definition, completeness of AIDS case reporting in hospitals (> or = 93%) and outpatient settings (> or = 90%) was high. Agreement between the information provided on the original case report and the medical record was > 98% for sex, > 83% for each race/ethnicity group; and > 67% for each risk group. The median reporting delay after the change was four months, but varied by site from three to six months.

CONCLUSIONS

The completeness, validity, and timeliness of the AIDS surveillance system remains high after the 1993 change in the surveillance case definition. These findings might be useful for programs implementing integrated HIV and AIDS surveillance systems.

Folic acid: are current fortification levels adequate?

OBJECTIVE

Beginning on January 1, 1998, all cereal and grain products in the United States were fortified with folic acid to reduce the occurrence of the very common congenital malformations known as neural-tube defects. Three years have passed since the fortification program began, and it is time to evaluate whether the current fortification levels have met their intended objective.

METHODS

We offer an overview of folate and its potential role in the etiology of neural-tube defects, review some of the highlights of the deliberations that led to the decision by the Food and Drug Administration to fortify the food supply, and offer a perspective on how to measure whether current fortification levels are adequate.

RESULTS

There is no national system in the United States that monitors neural-tube and other birth defects over time, and no postmarketing surveillance was mandated to monitor the safety of the fortification program. Therefore, we must evaluate the program in other ways. Blood biomarkers of folate status such as the levels of folate in red blood cells and homocysteine in plasma provided the best evidence of the effectiveness of the folic-acid-fortification program because of their relatively high sensitivities in relation to their specificities as markers of folate status. In addition, these biomarkers might provide information about the risks of other diseases related to folate status such as vascular disease.

CONCLUSION

Federal agencies should coordinate efforts to gather and evaluate markers of folate status at the population level. These measures can be used to evaluate the safety and efficacy of folic-acid fortification and whether changes are warranted in fortification levels.

Perinatal mortality and neonatal morbidity rates among twin pairs at different gestational ages: optimal delivery timing at 37 to 38 weeks' gestation

OBJECTIVE

The aim of this study was to determine the gestational age at delivery associated with the lowest rates of perinatal mortality, respiratory distress syndrome, and long hospital stays among twins, with pair rates used to account for both infants in each twin pregnancy.

STUDY DESIGN

We conducted a population-based retrospective study that analyzed linked birth certificates, fetal and infant death certificates, and hospital discharge data for 8150 twin pairs born in Washington State during 1987 through 1997. The chi2 or Fisher exact test was used to assess the statistical significance.

RESULTS

The nadirs of perinatal mortality rate, respiratory distress syndrome incidence, and long hospital stay rate were seen at delivery dates of 39, 40, and 38 weeks' gestation, respectively. Restriction to pairs delivered vaginally without the induction of labor revealed that the perinatal mortality rate was lowest for delivery at 37 weeks' gestation, the gestational age at which the highest numbers of such spontaneously timed pairs were born.

CONCLUSION

Induction of labor should be routinely considered for twins at 37 to 38 weeks' gestation.

Sensitivity and predictive value positive measurements for public health surveillance systems

Two important measurements for the evaluation of a public health surveillance system are sensitivity and predictive value positive (PVP). The computation of sensitivity and PVP for a public health surveillance system, however, can be complicated by the absence of an appropriate gold standard. In addition, there are few references for the computation of sensitivity and PVP for a surveillance system. To determine how these attributes of evaluation have been reported in epidemiologic literature, I review papers that report sensitivity and PVP for public health surveillance systems. Of the 31 papers that met selection criteria, 21 (68%) included either a reference for the computation or a definition of the attributes, whereas 18 (58%) reported both attributes. All 31 papers reported sensitivity, and among the 31 papers, 24 (77%) reported more than one sensitivity measurement. Among the 18 papers that reported at least PVP, 13 (72%) reported more than one PVP measurement. This review provides guidance in computing sensitivity and PVP for a public health surveillance system.

Pregnancy outcomes among U.S. women Vietnam veterans

BACKGROUND

Since the 1965-1975 Vietnam War, there has been persistent concern that women who served in the U.S. military in Vietnam may have experienced adverse pregnancy outcomes.

METHODS

We compared self-reported pregnancy outcomes for 4,140 women Vietnam veterans with those of 4,140 contemporary women veterans who were not deployed to Vietnam. As a measure of association, we calculated odds ratios (OR) and 95% confidence intervals (CI) using logistic regression adjusting for age at conception, race, education, military nursing status, smoking, drinking and other exposures during pregnancy.

RESULTS

There was no statistically significant association between military service in Vietnam and index pregnancies resulting in miscarriage or stillbirth, low birth weight, pre-term delivery, or infant death. The risk of having children with "moderate-to-severe" birth defects was significantly elevated among Vietnam veterans (adjusted OR = 1.46, 95% CI = 1.06-2.02).

CONCLUSIONS

The risk of birth defects among index children was significantly associated with mother's military service in Vietnam.

Congenital anomalies ascertained by two record systems run in parallel in the Canadian Province of Alberta

To assess the quality and appropriateness of Canadian Congenital Anomalies Surveillance System (CCASS), a system based on routine hospital admission/separation records, we compared the congenital anomalies ascertained by CCASS for the period of January 1, 1990 to December 31, 1993 in the province of Alberta with corresponding figures obtained from Alberta Congenital Anomalies Surveillance System (ACASS), a specific-purpose surveillance program collecting information on congenital anomalies from multiple sources with mechanisms to evaluate diagnosis. Rates of congenital anomalies estimated by CCASS tended to be higher. Agreement between CCASS and ACASS depended on diagnosis: for the International Clearinghouse for Birth Defects Monitoring System standard categories of congenital anomalies (except for anomalies of abdominal wall), agreement usually exceeded 50%; for less clear-cut diagnoses, it was well below 50%. We conclude that routine medical records can be used for surveillance purposes for major congenital anomalies with clear-cut diagnosis.

Identifying Pregnant Substance Abusers and Studying Their Treatment Using Birth Certificates, Medicaid Claims, and State Substance Abuse Treatment Data

A substantial body of recent research has focused on the prevalence of substance abuse among pregnant women, Its effects on maternal and infant health, ways to identify and effectively treat pregnant women, and the cost of care for pregnant women and their infants. However, this research has been hampered by a lack of data, particularly at the state and local levels. The potential benefits of such research for improving treatment and other services to this high-risk group make it important to continue to develop accurate and timely data sources. This study builds on previous work that investigated the quality of birth certificate and Medicaid data as well as previous efforts to merge these two data sources by augmenting the merged birth certificates and Medicaid data with data on a group of known substance abusers - those in substance abuse treatment. The purpose of merging these records is to improve the identification of pregnant substance abusers and, more importantly, to provide an enriched data source of variables from all three sources. Using merged data from two example states, we show that linked birth certificates, Medicaid claims, and state substance abuse treatment files provide a useful source of information for studying the birth outcomes and costs for pregnant women in substance abuse treatment. However, certain groups, such as women who do not obtain any health care or substance abuse treatment, will be underrepresented in such a database. Consequently, efforts at more complete surveillance of pregnant substance abusers should be undertaken, perhaps through increased efforts to improve reporting on the birth certificate, which is a universal document.

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.

Potential influence of migration bias in birth cohort studies

OBJECTIVE

To assess the potential bias, due to migration from the community, in a birth cohort study of learning disability in Olmsted County, Minnesota.

MATERIAL AND METHODS

The 1976 through 1982 birth cohort consisted of 8,548 children born to mothers who were residents of Rochester, Minnesota, at the time of delivery. The current status of all children was determined for the 1995 to 1996 school year with the resources of Independent School District #535, the Rochester Epidemiology Project, and the Rochester Reading Center. Information from birth certificates was compared between migrants and nonmigrants with use of standard statistical tests.

RESULTS

The cumulative probability of migration by age 5 years was 32.2% (95% confidence interval, 31.2 to 33.2%). When migrants were compared with nonmigrants, the distributions of Apgar scores, father's age, gestational age at birth, and number of children in the family were virtually identical. In contrast, migrants were more likely to be nonwhite (6% versus 2%), be born to a single parent (11% versus 7%), and have a congenital defect noted at birth (1.5% versus 0.7%). When considered simultaneously in a logistic regression model, the parents of migrants were more highly educated, migrant mothers were younger and had fewer prenatal visits, and migrant children were more likely to be black.

CONCLUSION

This report demonstrates the extreme effort that must be made to assemble a birth cohort in our mobile society. Furthermore, the results suggest that only slight differences exist between migrants and nonmigrants; these are unlikely to compromise the future results of the ongoing learning disability study.

How well do birth certificates describe the pregnancies they report? The Washington State experience with low-risk pregnancies

OBJECTIVES

Birth certificates are a major source of population-based data on maternal and perinatal health, but their value depends on the accuracy of the data. This study assesses the validity of information recorded on the birth certificates for women in Washington State who were considered to be low risk at entry into care.

METHODS

Birth certificates were matched to data abstracted from prenatal and intrapartum clinic and hospital records of a sample of 1937 Washington State obstetrical patients who were considered to be low risk at the beginning of their pregnancies. Accuracy of a variety of pregnancy characteristics (e.g., complications, procedures) on the birth certificate was analyzed using percentage agreement and sensitivity with record abstracts as the "gold standard." Next, we weighted the data from each source to produce estimates of pregnancy characteristics in the population. We compared these estimates from the two data sources to see whether they provide similar pictures of this subpopulation.

RESULTS

Missing data for specific items on the birth certificates ranged from 0% to 24%. The birth certificate accurately captured gravidity and parity, but was less likely to report prenatal and intrapartum complications. The population estimates of the two data sources were significantly different.

CONCLUSIONS

Because birth certificates significantly underestimated the complications of pregnancies, number of interventions, number of procedures, and prenatal visits, use of these data for health policy development or resource allocation should be tempered with caution.

Validity of insurance information on California birth certificates

OBJECTIVES

This study assessed the validity of health insurance information on California birth certificates.

METHODS

Insurance information from birth certificates and linked face-to-face interviews was compared for 7428 postpartum women in California.

RESULTS

There was excellent agreement between insurance information in birth certificate and interview data, especially when capitated plans were grouped with all other private coverage. Analyses using both data sources produced similar estimates of the likelihood of untimely prenatal care according to type of insurance coverage.

CONCLUSIONS

Birth certificate data including insurance information appear to be an appropriate resource for examining both the extent of coverage for maternity care and associations between prenatal care use and insurance status.