Are we underestimating rates of vaginal birth after previous cesarean birth? The validity of delivery methods from birth certificates

Autism Spectrum Disorder and Neonatal Serum Magnesium Levels in Preterm Infants

Premature birth is associated with increased risk of autism spectrum disorder. Antenatal maternal magnesium administration is known to reduce subsequent risk of cerebral palsy including among premature infants, suggesting a potentially broader neuroprotective role for magnesium. Our objective was to determine whether magnesium could be protective against autism spectrum disorders in premature infants. A cohort of 4855 preterm children was identified, magnesium levels from 24 to 48 hours of life recorded, and subsequent autism spectrum disorder status determined. Adjusted relative risk of autism spectrum disorder with each 1 mg/dL increase in neonatal magnesium level was 1.15 (95% confidence interval: 0.86-1.53). Analysis of variance indicated that magnesium levels varied by gestational age and maternal antenatal magnesium supplementation, but not autism spectrum disorder status (F_1,4824 = 1.43, P = .23). We found that neonatal magnesium levels were not associated with decreased autism spectrum disorder risk. Future research into autism spectrum disorder risks and treatments in premature infants is needed.

Atrazine Contamination of Drinking Water and Adverse Birth Outcomes in Community Water Systems with Elevated Atrazine in Ohio, 2006⁻2008

Atrazine, a common water contaminant in the U.S., has been associated with adverse birth outcomes in previous studies. This study aimed to determine if atrazine concentrations in drinking water are associated with adverse birth outcomes including small for gestational age (SGA), term low birth weight (term LBW), very low birth weight (VLBW), preterm birth (PTB), and very preterm birth (VPTB). This study included 14,445 live singleton births from Ohio communities served by 22 water systems enrolled in the U.S. Environmental Protection Agency's Atrazine Monitoring Program between 2006 and 2008. Mean gestational and trimester-specific atrazine concentrations were calculated. Significantly increased odds of term LBW birth was associated with atrazine exposure over the entire gestational period (OR 1.27, 95% CI 1.10, 1.45), as well as the first (OR 1.20, 95% CI 1.08, 1.34) and second trimesters (OR 1.13, 95% CI 1.07, 1.20) of pregnancy. We observed no evidence of an association between atrazine exposure via drinking water and SGA, VLBW, PTB, or VPTB. Our results suggest that atrazine exposure is associated with reduced birth weight among term infants and that exposure to atrazine in drinking water in early and mid-pregnancy may be most critical for its toxic effects on the fetus.

Arsenic in drinking water and adverse birth outcomes in Ohio

BACKGROUND

Arsenic in drinking water has been associated with adverse reproductive outcomes in areas with high levels of naturally occurring arsenic. Less is known about the reproductive effects of arsenic at lower levels.

OBJECTIVES

This research examined the association between low-level arsenic in drinking water and small for gestational age (SGA), term low birth weight (term LBW), very low birth weight (VLBW), preterm birth (PTB), and very preterm birth (VPTB) in the state of Ohio.

METHODS

Exposure was defined as the mean annual arsenic concentration in drinking water in each county in Ohio from 2006 to 2008 using Safe Drinking Water Information System data. Birth outcomes were ascertained from the birth certificate records of 428,804 births in Ohio from the same time period. Multivariable generalized estimating equation logistic regression models were used to assess the relationship between arsenic and each birth outcome separately. Sensitivity analyses were performed to examine the roles of private well use and prenatal care utilization in these associations.

RESULTS

Arsenic in drinking water was associated with increased odds of VLBW (AOR 1.14 per µg/L increase; 95% CI 1.04, 1.24) and PTB (AOR 1.10; 95% CI 1.06, 1.15) among singleton births in counties where <10% of the population used private wells. No significant association was observed between arsenic and SGA, or VPTB, but a suggestive association was observed between arsenic and term LBW.

CONCLUSIONS

Arsenic in drinking water was positively associated with VLBW and PTB in a population where nearly all (>99%) of the population was exposed under the current maximum contaminant level of 10µg/L. Current regulatory standards may not be protective against reproductive effects of prenatal exposure to arsenic.

Maternal prenatal weight gain and autism spectrum disorders

BACKGROUND

The rising population of individuals identified with an autism spectrum disorder (ASD) calls for further investigation of its underlying etiology. A disturbance in the fetal steroid hormone environment may be a mechanism in which environmental and genetic risk factors interact. The mother, fetus, and placenta collectively create the fetal steroid environment. Prepregnancy BMI and pregnancy weight gain have served as markers for fetal steroid hormone exposure in other disease states. This study's objective is to determine whether prepregnancy BMI and pregnancy weight gain are associated with increased ASD risk across study designs and cohorts while controlling for important confounding variables.

METHODS

A population-based Utah ASD cohort (n = 128) was ascertained in a 3-county surveillance area and gender- and age-matched to 10,920 control subjects. A second, research-based ASD cohort of Utah children (n = 288) and their unaffected siblings (n = 493) were ascertained through participation in an ASD genetics study. Prenatal variables were obtained from birth certificate records.

RESULTS

ASD risk was significantly associated with pregnancy weight gain (adjusted odds ratio = 1.10, 95% confidence interval: 1.03 to 1.17; adjusted odds ratio = 1.17, 95% confidence interval: 1.01 to 1.35 for each 5 pounds of weight gained), but not prepregnancy BMI, in population and research-based cohorts, respectively. When analyses were restricted to ASD cases with normal IQ, these associations remained significant.

CONCLUSIONS

ASD risk associated with a modest yet consistent increase in pregnancy weight gain suggests that pregnancy weight gain may serve as an important marker for autism's underlying gestational etiology. This justifies an investigation into phenomena that link pregnancy weight gain and ASD independent of prepregnancy BMI.

Prenatal and perinatal factors associated with intellectual disability

Prenatal and perinatal risk factors associated with intellectual disability (ID) were studied in 8-year-old Utah children from a 1994 birth cohort (N  =  26,108) using broad ascertainment methods and birth records following the most current recording guidelines. Risk factor analyses were performed inclusive and exclusive of children with a known or suspected underlying genetic disorder. Risk factors identified were poly/oligohydramnios, advanced paternal/maternal age, prematurity, fetal distress, premature rupture of membranes, primary/repeat cesarean sections, low birth weight, assisted ventilation greater than 30 min, small-for-gestational age, low Apgar scores, and congenital infection. Although several risk factors lost significance once children with underlying genetic disorders were excluded, socioeconomic variables were among those that maintained a prominent association with increased ID risk.

Hospital data reporting on postpartum hemorrhage: under-estimates recurrence and over-estimates the contribution of uterine atony

This study aimed to explore whether recording of a prior adverse pregnancy outcome (postpartum hemorrhage) in a medical record increases the likelihood that recurrence of the same event is reported in hospital data. Using a sample of 588 pregnancies [2 consecutive pregnancies for 294 randomly selected women with at least one postpartum hemorrhage (PPH)], we compared 'coded' recurrence rates in hospital data with those obtained from medical record audit. 'Coded' recurrence in a second pregnancy was also compared for women with or without a documented history of prior PPH. We found a 'coded' recurrence rate of 18.5% and an 'audited' recurrence rate of 28.4%. The 'coded' rate of recurrence among women who had a documented history of PPH was 27.4% compared to 19.1% when the previous PPH was not noted in the second pregnancy medical record. Medical record reporting of uterine atony as the cause for postpartum hemorrhages in first and second births was 37.9 and 34.0% while 'coded' hospital data reporting attributed 79.8 and 73.9% respectively to atony. Our study results indicate that a history of postpartum hemorrhage may be a stronger risk factor for subsequent PPH than previously demonstrated. A recorded history of PPH was associated with an increased likelihood of reporting a subsequent PPH, and in such cases recurrence rates approximate true recurrence. The contribution of uterine atony as a cause of postpartum hemorrhage is over-estimated using hospital data.

Is the accuracy of prior preterm birth history biased by delivery characteristics?

To assess the sensitivity of birth certificates to preterm birth history and determine whether omissions are randomly or systemically biased. Subjects who experienced a preterm birth followed by a subsequent pregnancy were identified in a regional database. The variable "previous preterm birth" was abstracted from birth certificates of the subsequent pregnancy. Clinical characteristics were compared between subjects who were correctly versus incorrectly coded. 713 subjects were identified, of whom 65.5% were correctly coded in their subsequent pregnancy. Compared to correctly coded patients, patients who were not correctly identified tended to have late and non-recurrent preterm births or deliveries that were secondary to maternal or fetal indications. A recurrence of preterm birth in the subsequent pregnancy was also associated with correct coding. The overall sensitivity of birth certificates to preterm birth history is suboptimal. Omissions are not random, and are associated with obstetrical characteristics from both the current and prior deliveries. As a consequence, resulting associations may be flawed.

Ambient air pollution and the risk of stillbirth

The purpose of the present study was to examine the risk of stillbirth associated with ambient air pollution during pregnancy. Using live birth and fetal death data from New Jersey from 1998 to 2004, the authors assigned daily concentrations of air pollution to each birth or fetal death. Generalized estimating equation models were used to estimate the relative odds of stillbirth associated with interquartile range increases in mean air pollutant concentrations in the first, second, and third trimesters and throughout the entire pregnancy. The relative odds of stillbirth were significantly increased with each 10-ppb increase in mean nitrogen dioxide concentration in the first trimester (odds ratio (OR) = 1.16, 95% confidence interval (CI): 1.03, 1.31), each 3-ppb increase in mean sulfur dioxide concentration in the first (OR = 1.13, 95% CI: 1.01, 1.28) and third (OR = 1.26, 95% CI: 1.03, 1.37) trimesters, and each 0.4-ppm increase in mean carbon monoxide concentration in the second (OR = 1.14, 95% CI: 1.01, 1.28) and third (OR = 1.14, 95% CI: 1.06, 1.24) trimesters. Although ambient air pollution during pregnancy appeared to increase the relative odds of stillbirth, further studies are needed to confirm these findings and examine mechanistic explanations.

Trends and risk factors of stillbirth in New Jersey 1997-2005

INTRODUCTION

The purpose of this study was to examine the trends in the rates of stillbirth by race and ethnicity and to determine the risk factors of stillbirth.

METHODS

We used New Jersey data (1997-2005) for live births and fetal deaths. Cox proportional hazards model was used to estimate the risk of stillbirth associated with maternal risk factors and pregnancy complications.

RESULTS

The rate of stillbirth was 4.4/1000 total births (3.4 for white and 7.9 for black non-Hispanics and 4.4 for Hispanics/1000 total births). The rates of stillbirth decreased from 3.8 in 1997 to 2.7/1000 total births in 2005 for white non-Hispanics but remained unchanged for other race/ethnicity groups. Adjusted relative risks for the risk factors associated with stillbirth were 1.3 (95% CI, 1.2-1.4) for maternal age ≥ 35 years, 1.9 (95% CI, 1.7-2.1) for black non-Hispanics, 2.8 (95% CI, 2.4-3.3) for no prenatal care, 40.2 (95% CI, 36.9-43.9) for placental abruption, 5.3 (95% CI, 3.4-8.2) for eclampsia, 3.5 (95% CI, 2.8-4.3) for diabetes mellitus and 1.7 (95% CI, 1.3-2.2) for preeclampsia.

CONCLUSION

There was a decline in the rate of stillbirth but there were persistent racial disparities with the highest rates of stillbirth for black non-Hispanics.

U.S. Maternally linked birth records may be biased for Hispanics and other population groups

PURPOSE

We sought to advance understanding of linkage error in U.S. maternally linked datasets and how the error might affect results of studies based on the linked data.

METHODS

North Carolina birth and fetal death records for 1988-1997 were maternally linked (n=1,030,029). The maternal set probability, defined as the probability that all records assigned to the same maternal set do in fact represent events to the same woman, was used to assess differential maternal linkage error across race/ethnic groups.

RESULTS

Maternal set probabilities were lower for records specifying Asian or Hispanic race/ethnicity, suggesting greater maternal linkage error for these sets. The lower probabilities for Hispanics were concentrated in women of Mexican origin who were not born in the United States.

CONCLUSIONS

Differential linkage error may be a source of bias in studies that use U.S. maternally linked datasets to make comparisons between Hispanics and other groups or among Hispanic subgroups. Methods to quantify and adjust for this potential bias are needed.

Trends in birth weight and gestational length among singleton term births in the United States: 1990-2005

OBJECTIVE

To estimate changes over time in birth weight for gestational age and in gestational length among term singleton neonates born from 1990 to 2005.

METHODS

We used data from the U.S. National Center for Health Statistics for 36,827,828 singleton neonates born at 37-41 weeks of gestation, 1990-2005. We examined trends in birth weight, birth weight for gestational age, large and small for gestational age, and gestational length in the overall population and in a low-risk subgroup defined by maternal age, race or ethnicity, education, marital status, smoking, gestational weight gain, delivery route, and obstetric care characteristics.

RESULTS

In 2005, compared with 1990, we observed decreases in birth weight (-52 g in the overall population, -79 g in a homogenous low-risk subgroup) and large for gestational age birth (-1.4% overall, -2.2% in the homogenous subgroup) that were steeper after 1999 and persisted in regression analyses adjusted for maternal and neonate characteristics, gestational length, cesarean delivery, and induction of labor. Decreases in mean gestational length (-0.34 weeks overall) were similar regardless of route of delivery or induction of labor.

CONCLUSION

Recent decreases in fetal growth among U.S., term, singleton neonates were not explained by trends in maternal and neonatal characteristics, changes in obstetric practices, or concurrent decreases in gestational length.

LEVEL OF EVIDENCE

III.

Cross-sectional reporting of previous Cesarean birth was validated using longitudinal linked data

OBJECTIVE

The aim of this study was to demonstrate the feasibility of using linked health records to assess data quality in population health data.

STUDY DESIGN AND SETTING

Reproductive histories of 155,897 women were constructed by longitudinal linkage of the New South Wales (Australia) birth records in 1998-2005, and 127,952 birth and hospital discharge records in 2000-2005 were cross-sectionally linked. History of Cesarean section (CS) derived from the longitudinal linkage ("gold standard") was used to validate the CS history fields (i.e., "Was the last birth by Cesarean section?" and "Total number of previous Cesarean sections?") in birth records and to validate "vaginal birth after previous Cesarean (VBAC)" and "maternal care for uterine scar" in hospital records.

RESULTS

The reporting of CS at last birth was reliable with sensitivity, specificity, positive predictive value (PPV), and negative predictive value all >95% as was the number of previous CS (weighted kappa=0.97). For the hospital data, sensitivity and PPV were 46% and 99% for VBAC, 92% and 99% for maternal care of uterine scar, and 85% and 99%, respectively, for any prior CS.

CONCLUSION

Assessing data quality by record linkage is feasible and can be done more quickly and cheaply than by any traditional validation study.

Prenatal, perinatal, and neonatal factors associated with autism spectrum disorders

OBJECTIVE

To investigate prenatal, perinatal, and neonatal risk factors for autism spectrum disorders by using participants identified through broad ascertainment and reliable classification methods.

METHODS

The targeted population was 8-year-old children born in 1994 and residing in 1 of the 3 most populous counties in Utah who were identified as having an autism spectrum disorder on the basis of methodology used by the 2002 Autism and Developmental Disabilities Monitoring Network. Of those identified, 132 children (115 boys, 17 girls) had birth certificate records available. Each child was matched by gender and birth year to 100 controls (11 500 boys, 1700 girls) from the birth certificate database in a nested case-control design. Birth certificate records of participants and controls were surveyed for 23 potentially pathologic prenatal, perinatal, and neonatal factors.

RESULTS

The prenatal factors that occurred significantly more frequently among children with autism spectrum disorders were advanced maternal age and parity. Increased duration of education among mothers of children with autism spectrum disorders was small but statistically significant. Significant perinatal factors were breech presentation and primary cesarean delivery. When corrected for breech presentation, a known indication for cesarean delivery, the association between primary cesarean delivery and autism spectrum disorders was eliminated. There were no significant associations found between autism spectrum disorders and neonatal factors.

CONCLUSIONS

In the absence of other complications suggesting fetal distress, the association between breech presentation and autism spectrum disorders in this study suggests a shared etiology rather than causal relationship. Additional investigation focused on both genetic and environmental factors that link these autism spectrum disorder risk factors individually or collectively is needed.

Ambient air pollutant concentrations during pregnancy and the risk of fetal growth restriction

BACKGROUND

Previous studies of air pollution and birth outcomes have not evaluated whether complicated pregnancies might be susceptible to the adverse effects of air pollution. It was hypothesised that trimester mean pollutant concentrations could be associated with fetal growth restriction, with larger risks among complicated pregnancies.

METHODS

A multiyear linked birth certificate and maternal/newborn hospital discharge dataset of singleton, term births to mothers residing in New Jersey at the time of birth, who were white (non-Hispanic), African-American (non-Hispanic) or Hispanic was used. Very small for gestational age (VSGA) was defined as a fetal growth ratio <0.75, small for gestational age (SGA) as > or =0.75 and <0.85, and 'reference' births as > or =0.85. Using polytomous logistic regression, associations between mean pollutant concentrations during the first, second and third trimesters and the risks of SGA/VSGA were examined, as well as effect modification of these associations by several pregnancy complications.

RESULTS

Significantly increased risk of SGA was associated with first and third trimester PM(2.5) (particulate matter <2.5 microm in aerodynamic diameter), and increased risk of VSGA associated with first, second and third trimester nitrogen dioxide (NO(2)) concentrations. Pregnancies complicated by placental abruption and premature rupture of the membrane had approximately two- to fivefold greater excess risks of SGA/VSGA than pregnancies not complicated by these conditions, although these estimates were not statistically significant.

CONCLUSIONS

These findings suggest that ambient air pollution, perhaps specifically traffic emissions during early and late pregnancy and/or factors associated with residence near a roadway during pregnancy, may affect fetal growth. Further, pregnancy complications may increase susceptibility to these effects in late pregnancy.

Trends in rural and urban deliveries and vaginal births: California 1998-2002

CONTEXT

Pregnant women in rural areas may give birth in either rural or urban hospitals. Differences in outcomes between rural and urban hospitals may influence patient decision making.

PURPOSE

Trends in rural and urban obstetric deliveries and neonatal and maternal mortality in California were compared to inform policy development and patient and provider decision making in rural health care settings.

METHODS

Deliveries in California hospitals identified by the California Department of Health Services, Birth Statistical Master Files for years 1998 through 2002 were analyzed. Three groups of interest were created: rural hospital births to all mothers, urban hospital births to rural mothers, and urban hospital births to urban mothers.

FINDINGS

Of 2,620,096 births analyzed, less than 4% were at rural hospitals. Neonatal death rates were significantly higher in babies born to rural mothers with no pregnancy complications who delivered a normal weight baby vaginally at an urban hospital compared to urban mothers delivering at an urban hospital (0.2 [CI 0.2-0.4] deaths per 1,000 births versus 0.1 [CI 0.1-0.1]). Logistic regression analysis showed that delivery in a rural hospital was a protective factor compared to urban mothers delivering in an urban hospital, with an odds ratio of 0.8 (CI 0.6-0.9). Maternal death rates were not different.

CONCLUSIONS

Rural obstetric services in this period showed favorable neonatal and maternal safety profiles. This information should reassure patients considering a rural hospital delivery, and aid policy makers and health care providers striving to ensure access to obstetric services for rural populations.

Primary cesarean delivery among parous women in the United States, 1990-2003

OBJECTIVE

To explore trends in primary cesarean delivery rates among parous women with singleton pregnancies in the United States between 1990 and 2003.

METHODS

The analysis used data from national birth files based on U.S. birth certificates between 1990 and 2003. The primary cesarean delivery rate was defined as the number of primary cesarean deliveries per 100 deliveries among parous women with singleton pregnancies who have not had a previous cesarean delivery. A stratified analysis was employed to investigate whether trends varied by maternal age, gestational age, race/ethnicity, or region.

RESULTS

In the United States, the primary cesarean delivery rate among parous women decreased modestly from 7.1% in 1990 to 6.6% in 1996 but increased progressively to 9.3% in 2003. The increase in cesarean rates from 1996 to 2003 varied substantially by race/ethnicity: Hispanic and non-Hispanic white women exhibited lower and similar rates, whereas rates for non-Hispanic black women were consistently higher and rose by a far greater extent across the years. There were substantial differences in cesarean delivery trends across geographic divisions, with greatest increases observed in the mid-Atlantic, South Central, and South Atlantic areas of the United States. Primary cesarean rates also declined considerably with increasing gestational age.

CONCLUSION

Similar to the overall cesarean delivery rate, primary cesarean rates among parous women with singleton pregnancies have increased substantially in the United States since 1996.

LEVEL OF EVIDENCE

III.

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.

A new method for measuring misclassification of maternal sets in maternally linked birth records: true and false linkage proportions

OBJECTIVES

Numerous studies have used maternally linked birth records to investigate perinatal outcomes, maternal behaviors, and the quality of vital records birth data. Little attention has been given to assessing errors in the linkages and to understanding how such errors affect estimates derived from the linked data. The author developed a framework for conceptualizing maternal linkage error and measures for quantifying it, and examined the behavior of the new measures in a maternally linked file.

METHODS

Linkage errors were conceptualized as misclassification, with the classes being the maternal sets (records classified as representing different births to the same woman). The true linkage proportion, analogous to sensitivity, was used to capture the degree to which all of a woman's births were assigned to a single maternal set; the false linkage proportion, analogous to specificity, was used to capture the degree to which the assigned maternal sets combined births from different women. The behavior of the two proportions was examined by introducing increasing degrees of linkage error into a maternally linked file.

RESULTS

Both measures indicated greater misclassification with increasing simulated linkage errors.

CONCLUSIONS

The new measures may be a useful tool for assessing the quality of maternally linked data, as well as other types of linked records where the linkages are within a single file. This is a necessary step towards developing methods for addressing misclassification bias in studies of maternally linked records through sensitivity analysis, adjustment, and other means.

Maternal and birth characteristics in relation to childhood leukaemia

Our objective was to investigate the association of childhood leukaemia with selected maternal and birth characteristics by conducting a population-based case-control study using linked cancer registry and birth certificate records for Washington State. We compared maternal and infant characteristics of 595 Washington-born residents <20 years old with leukaemia diagnosed during 1981-2003, and 5,950 control children, using stratified analysis and logistic regression. Maternal age 35+ years (odds ratio [OR] 1.5; 95% confidence interval [CI] 1.1, 2.0), infant birthweight 4,000+ g (OR 1.4; 95% CI 1.1, 1.8), neonatal jaundice (OR 1.5; 95% CI 1.1, 2.1), and Down's syndrome (OR 31.3; 95% CI 6.4, 153.4) were associated with an increased risk of leukaemia. Among women with 2+ pregnancies, having at least two prior early (<20 weeks' gestation) fetal deaths was also associated with an increased risk (OR 1.5; 95% CI 0.97, 2.1). Maternal unmarried status (OR 0.7; 95% CI 0.6, 0.9) and African American race (OR 0.5; 95% CI 0.3, 0.9) were associated with a decreased risk. These results were more marked for acute lymphocytic leukaemia (ALL) than for acute myeloid leukaemia (AML), and for leukaemia diagnosed <5 years of age. These results may provide clues to the aetiology of childhood leukaemia. Genetic epidemiological studies are needed to expand our knowledge of inherent and possibly prenatal influences on the occurrence of this disease.

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.

Vaginal birth after cesarean in California: before and after a change in guidelines

PURPOSE

In 1999 the American College of Obstetricians and Gynecologists (ACOG) adopted more-restrictive guidelines for vaginal birth after cesarean delivery (VBAC). This study assesses trends in VBAC in California and compares neonatal and maternal mortality rates among women attempting VBAC delivery or undergoing repeat cesarean delivery before and after this guideline revision.

METHODS

The 1996 through 2002 California Birth Statistical Master Files were used to identify 386,232 California residents who previously gave birth by cesarean delivery and had a singleton birth planned in a California hospital.

RESULTS

Attempted VBAC deliveries decreased significantly from 24% before to 13.5% after guideline revision (P <.001). Neonatal mortality rates per 1,000 live births for attempted VBAC deliveries were not different from repeat cesarean delivery rates among neonates weighing > or =1,500 g in either the study periods 1996 to 1999 or 2000 to 2002. Neonatal mortality rates for attempted VBAC deliveries were higher for repeat cesarean deliveries among neonates weighing <1,500 g in the same periods (attempted VBAC: 1996-1999, 253.2; 95% Poisson confidence interval [CI], 197.7-308.6; 2000-2002, 336.8; CI, 254.3-419.4; repeat cesarean delivery: 1996-1999, 59.1; CI, 48.3-69.9; 2000-2002, 60.5, CI, 48.4-72.5). Maternal death rates per 100,000 live births for attempted VBAC deliveries were similar for both periods (1996-1999, 2.0; CI, 0.1-11.0; 2000-2002, 8.5; CI, 1.0-30.6).

CONCLUSIONS

Neonatal and maternal mortality rates did not improve despite increasing rates of repeat cesarean delivery during the years after the ACOG 1999 VBAC guideline revision. Women with infants weighing > or =1,500 g encountered similar neonatal and maternal mortality rates with VBAC or repeat cesarean delivery.

Maternal risk profiles and the primary cesarean rate in the United States, 1991-2002

OBJECTIVES

We examined factors contributing to shifts in primary cesarean rates in the United States between 1991 and 2002.

METHODS

US national birth certificate data were used to assess changes in primary cesarean rates stratified according to maternal age, parity, and race/ethnicity. Trends in the occurrence of medical risk factors or complications of labor or delivery listed on birth certificates and the corresponding primary cesarean rates for such conditions were examined.

RESULTS

More than half (53%) of the recent increase in overall cesarean rates resulted from rising primary cesarean rates. There was a steady decrease in the primary cesarean rate from 1991 to 1996, followed by a rapid increase from 1996 to 2002. In 2002, more than one fourth of first-time mothers delivered their infants via cesarean. Changing primary cesarean rates were not related to general shifts in mothers' medical risk profiles. However, rates for virtually every condition listed on birth certificates shifted in the same pattern as with the overall rates.

CONCLUSIONS

Our results showed that shifts in primary cesarean rates during the study period were not related to shifts in maternal risk profiles.

Accuracy of reporting maternal in-hospital diagnoses and intrapartum procedures in Washington State linked birth records

While the impact of maternal morbidities and intrapartum procedures is a common topic in perinatal outcomes research, the accuracy of the reporting of these variables in the large administrative databases (birth certificates, hospital discharges) often utilised for such research is largely unknown. We conducted this study to compare maternal diagnoses and procedures listed on birth certificates, hospital discharge data, and birth certificate and hospital discharge data combined, with those documented in a stratified random sample of hospital medical records of 4541 women delivering liveborn infants in Washington State in 2000. We found that birth certificate and hospital discharge data combined had substantially higher true positive fractions (TPF, proportion of women with a positive medical record assessment who were positive using the administrative databases) than did birth certificate data alone for labour induction (86% vs. 52%), cephalopelvic disproportion (83% vs. 35%), abruptio placentae (85% vs. 68%), and forceps-assisted delivery (89% vs. 55%). For procedures available only in hospital discharge data, TPFs were generally high: episiotomy (85%) and third and fourth degree vaginal lacerations (91%). Except for repeat caesarean section without labour (TPF, 81%), delivery procedures available only in birth certificate data had low TPFs, including augmentation (34%), repeat caesarean section with labour (61%), and vaginal birth after caesarean section (62%). Our data suggest that researchers conducting perinatal epidemiological studies should not rely solely on birth certificate data to detect maternal diagnoses and intrapartum procedures accurately.

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.

Operative vaginal delivery and neonatal and infant adverse outcomes: population based retrospective analysis

OBJECTIVE

To compare the risk of neonatal and infant adverse outcomes between vacuum and forceps assisted deliveries.

DESIGN

Population based study.

SETTING

US linked natality and mortality birth cohort file and the New Jersey linked natality, mortality, and hospital discharge summary birth cohort file.

PARTICIPANTS

Singleton live births in the United States (n = 11 639 388) and New Jersey (n = 375 351).

MAIN OUTCOME MEASURES

Neonatal morbidity and mortality.

RESULTS

Neonatal mortality was comparable between vacuum and forceps deliveries in US births (odds ratio 0.94, 95% confidence interval 0.79 to 1.12). Vacuum delivery was associated with a lower risk of birth injuries (0.69, 0.66 to 0.72), neonatal seizures (0.78, 0.68 to 0.90), and need for assisted ventilation (< 30 minutes 0.94, 0.92 to 0.97; > or = 30 minutes 0.92, 0.88 to 0.98). Among births in New Jersey, vacuum extraction was more likely than forceps to be complicated by postpartum haemorrhage (1.22, 1.07 to 1.39) and shoulder dystocia (2.00, 1.62 to 2.48). The risks of intracranial haemorrhage, difficulty with feeding, and retinal haemorrhage were comparable between both modes of delivery. The sequential use of vacuum and forceps was associated with an increased risk of need for mechanical ventilation in the infant and third and fourth degree perineal tears.

CONCLUSION

Although vacuum extraction does have risks, it remains a safe alternative to forceps delivery.

Effects of maternal characteristics on cesarean delivery rates among U.S. Department of Defense healthcare beneficiaries, 1996-2002

BACKGROUND

National rates of cesarean birth continue a three decade-long escalation, despite widespread recognition that a reduction in the use of the procedure is a continuing appropriate public health goal, as evidenced by the Healthy People 2010 reduction targets. Nonclinical factors associated with cesarean delivery include maternal age, race, socioeconomic status, and insurance coverage. This study compared cesarean delivery rates and trends for the U.S. Department of Defense healthcare beneficiary population from 1996 to 2002 with those observed nationally, and assessed the association of these nonclinical factors with cesarean rate variation in the U.S. Department of Defense healthcare beneficiary population.

METHODS

Hospital discharge and claims records for babies born in the military and civilian hospitals that comprise the Department of Defense healthcare network were used to calculate total and primary cesarean delivery rates and vaginal birth after cesarean (VBAC) rates from 1996 to 2002. Annual cesarean rates for subgroups defined by maternal age, race, and socioeconomic status were calculated to examine rate variations and rate trends within the study population. Pooled data from 1999 to 2002 were used to compare rates across socioeconomic status, stratified by age and race. Statistical significance of the differences calculated for subgroups was assessed using chi-square.

RESULTS

Total and primary cesarean delivery rates among the U.S. Department of Defense population were lower than those reported nationally for every year examined. Cesarean delivery and VBAC rate trends in the national and Department of Defense populations were similar. Within the Department of Defense population, total cesarean delivery increased with increasing maternal age and was more highly associated with racial minorities relative to white women. The higher socioeconomic subgroup (defined as active duty, retired, and warrant officers and their families in this study) was generally associated with reduced cesarean delivery rates.

CONCLUSIONS

Cesarean deliveries are performed less frequently for the U.S. Department of Defense healthcare beneficiary population relative to the national population. Associations between socioeconomic factors and cesarean rates reported for the national population were not apparent in the study population. The consistent pattern of rate variation across racial subgroups in the Department of Defense population suggests that factors beyond those examined in this study are needed to explain the elevated cesarean rates for racial minorities.

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.

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.

Vaginal births after Caesarean (VBAC): a population study

This paper describes delivery outcomes for women from Victoria, Australia, who gave birth in 1995 and whose immediately previous (penultimate) delivery, within a 5-year search period, was a Caesarean section. Because of the large numbers of records involved, dedicated computer software for record linkage was used to identify the previous delivery and link it with the woman's current birth in 1995. Overall, 79% of the records from multiparous women were linked successfully. Approximately 15% were not linked because the previous birth was before the search period or was an abortion that would not have been reported to the Perinatal Data Collection Unit. Reasons for not being able to link the last 6% of the records include the previous pregnancy being overseas or interstate. Women who had a vaginal birth as the penultimate birth or a multiple birth at either event were excluded, resulting in a study population of 4663 linked records. More women (68%) had a repeat Caesarean than went into labour and, of the remaining women who laboured, 56% delivered vaginally. Overall, 18% of the women delivered vaginally. For the women who went into labour, the reported number experiencing a uterine rupture was two per 1000 births. Uterine rupture was not reported in the two-thirds who did not labour but had a repeat Caesarean. A review of the perinatal deaths identified only two deaths, one baby being born by elective Caesarean and one by a vaginal birth after a previous Caesarean (VBAC) where the choice of delivery methods may have contributed to the death. This large study is one of the few in the literature to provide population-based information on vaginal births after a previous Caesarean and related outcomes.

Cesarean delivery rates in the United States. The 1990s

The increase in CS rates in the United States in the 1970s and 1980s and the gradual decrease in the 1990s have been the focus of considerable attention because of the increased maternal morbidity and cost associated with the procedure without apparent impact on infant mortality. Focused efforts to reduce CS have resulted in a modest decrease the rate of primary CS and a marked increase in VBAC. Considerable variation in CS rates exists among regions in the United States and among states within those regions. The states with the higher CS rates are clustered in the South and Northeast regions of the United States, whereas rates tend to be lower in the West and Midwest. This variation cannot be explained by standard demographic risk factors and is likely related to local culture and mode of practice. Patient case mix should also be taken into account when comparing CS rates. Accounting for differences risk may help highlight differences in mode of practice and thus identify opportunities for improvement. Several reports from hospitals and communities of education and peer review programs have resulted in a significant reduction in their CS rates without increasing perinatal or maternal morbidity and mortality. A common theme in these reports of successful strategies to decrease the CS rate safely is the importance of physician motivation to make a change.