Validation of obstetric estimate using early ultrasound: 2007 California birth certificates

Assessing hospital differences in low-risk cesarean delivery metrics in Florida

BACKGROUND

Unnecessary cesarean deliveries lead to increased maternal and neonatal morbidities and mortalities. In 2020, Florida had a cesarean delivery rate of 35.9%, the third highest in the nation. An effective quality improvement strategy to reduce overall cesarean delivery rates is to decrease primary cesarean deliveries in low-risk births (nulliparous, term, singleton, vertex). Of note, 3 nationally accepted hospital measures of low-risk cesarean delivery rates include the nulliparous, term, singleton, vertex; Joint Commission; and Society for Maternal-Fetal Medicine metrics. Comparing metrics is necessary because accurate and timely measurement is essential to support multihospital quality improvement efforts to reduce low-risk cesarean delivery rates and improve the quality of maternal care.

OBJECTIVE

This study aimed to assess differences in hospital low-risk cesarean delivery rates in Florida using 5 different metrics of low-risk cesarean delivery rate based on (1) risk methodology, nulliparous, term, singleton, vertex; Joint Commission; and Society for Maternal-Fetal Medicine metrics, and (2) data source, linked birth certificate and hospital discharge records and hospital discharge records only.

STUDY DESIGN

This was a population-based study of live Florida births from 2016 to 2019 to compare 5 approaches to calculating low-risk cesarean delivery rates. Analyses were performed using linked birth certificate data and inpatient hospital discharge data. The 5 low-risk cesarean delivery measures were defined as follows: nulliparous, term, singleton, vertex birth certificate; Joint Commission-linked used Joint Commission exclusions; Society for Maternal-Fetal Medicine-linked used Society for Maternal-Fetal Medicine exclusions; Joint Commission hospital discharge with Joint Commission exclusions; and Society for Maternal-Fetal Medicine hospital discharge with Society for Maternal-Fetal Medicine exclusions. Nulliparous, term, singleton, vertex birth certificate was based on data from birth certificates and not using linked hospital discharge data. Designated as nulliparous, term, singleton, vertex, it does not exclude other high-risk conditions. The second and third measures (Joint Commission-linked used Joint Commission exclusions and Society for Maternal-Fetal Medicine-linked used Society for Maternal-Fetal Medicine exclusions) use data elements from the full-linked dataset to designate nulliparous, term, singleton, vertex and excluded several high-risk conditions. The last 2 measures (Joint Commission hospital discharge with Joint Commission exclusions; and Society for Maternal-Fetal Medicine hospital discharge with Society for Maternal-Fetal Medicine exclusions) were based on data from hospital discharge data only and not using linked birth certificate data. These measures generally reflect term, singleton, and vertex because parity could not be assessed adequately on hospital discharge data. Hospital differences between these 5 measures were calculated overall and by neonatal intensive care unit level.

RESULTS

Overall, the median of hospital low-risk cesarean rates decreased across the measures, from NTSV-BC 30.7%, to Joint Commission linked 29.1%, and Society for Maternal Fetal Medicine hospital discharge 29.2% with a large decrease to Joint Commission hospital discharge 19.4% and Society for Maternal Fetal Medicine hospital discharge 18.1%. A similar trend was seen by neonatal intensive care unit level. For each of the measures, level II had the highest median low-risk cesarean rates (nulliparous. term, singleton, vertex birth certificate) 32.7%, Joint Commission linked (31.4%), Society for Maternal Fetal Medicine linked: 31.1%, Society for Maternal Fetal Medicine hospital discharge 19.3%), except for level III Joint Commission hospital discharge (20.0%). A comparison of the median number of low-risk births overall and by neonatal intensive care unit level showed a decreasing number across the linked and hospital discharge measures. Again, a wide gap in low-risk cesarean delivery rates was identified between linked measures and hospital discharge measures. However, this gap narrowed as hospital rates increased.

CONCLUSION

Quality monitoring of low-risk cesarean delivery rates measured by the nulliparous, term, singleton, vertex metric using the birth certificate was fairly accurate and provided timely assessment for use by Florida hospitals. The nulliparous, term, singleton, vertex birth certificate rates were comparable with low-risk metrics using the linked data source. Overall, metrics used within the same data source had similar rates, with the Society for Maternal-Fetal Medicine metric having the lowest rates. Across data sources, metrics using hospital discharge data only resulted in substantially underestimated rates because of the inclusion of multiparous women and should be interpreted with caution.

Chronic Hypertension in Pregnancy and Racial-Ethnic Disparities in Complications

OBJECTIVE

To evaluate whether there are individual- and population-level associations between chronic hypertension and pregnancy complications, and to assess differences across seven racial-ethnic groups.

METHODS

This population-based study used linked vital statistics and hospitalization discharge data from all live and stillbirths in California (2008-2018), Michigan (2008-2020), Oregon (2008-2020), Pennsylvania (2008-2014), and South Carolina (2008-2020). We used multivariable log-binomial regression models to estimate risk ratios (RRs) and population attributable risk (PAR) percentages with 95% CIs for associations between chronic hypertension and several obstetric and neonatal outcomes, selected based on prior evidence and pathologic pathways. We adjusted models for demographic factors (race and ethnicity, payment method, educational attainment), age, body mass index, obstetric history, delivery year, and state, and conducted analyses stratified across seven racial-ethnic groups.

RESULTS

The study included 7,955,713 pregnancies, of which 168,972 (2.1%) were complicated by chronic hypertension. Chronic hypertension was associated with several adverse obstetric and neonatal outcomes, with the largest adjusted PAR percentages observed for preeclampsia with severe features or eclampsia (22.4; 95% CI 22.2-22.6), acute renal failure (13.6; 95% CI 12.6-14.6), and pulmonary edema (10.7; 95% CI 8.9-12.6). Estimated RRs overall were similar across racial-ethnic groups, but PAR percentages varied. The adjusted PAR percentages (95% CI) for severe maternal morbidity-a widely used composite of acute severe events-for people who were American Indian or Alaska Native, Asian, Black, Latino, Native Hawaiian or Other Pacific Islander, White, and Multiracial or Other were 5.0 (1.1-8.8), 3.7 (3.0-4.3), 9.0 (8.2-9.8), 3.9 (3.6-4.3), 11.6 (6.4-16.5), 3.2 (2.9-3.5), and 5.5 (4.2-6.9), respectively.

CONCLUSION

Chronic hypertension accounts for a substantial fraction of obstetric and neonatal morbidity and contributes to higher complication rates, particularly for people who are Black or Native Hawaiian or Other Pacific Islander.

Preterm birth among Pacific Islanders in the United States and the US-affiliated Pacific Islands: A systematic review and meta-analysis

OBJECTIVE

To better understand the epidemiology of preterm birth among Pacific Islanders in the United States and the US-Affiliated Pacific Islands.

METHODS

Systematic searches of MEDLINE, Embase, CINAHL, PsycINFO, two nonindexed regional journals, and gray literature were conducted and finalized in September 2021. Observational studies published since January 2010 that documented preterm birth outcomes among Pacific Islanders in the United States and the US-Affiliated Pacific Islands were eligible for inclusion. Outcomes of interest included preterm birth prevalence, risk compared with white women, and risk factors for preterm birth among Pacific Islanders.

RESULTS

Fourteen of the 3183 screened articles were included in meta-analyses. Random-effects models were used for pooled estimates with 95% confidence intervals. The pooled prevalence of preterm birth among Pacific Islanders was 11.2%, 95% CI: 9.3%-13.6%. Marshallese women had the highest pooled prevalence (20.7%, 95% CI 18.6%-23.0%) among Pacific Islander subgroups. Compared with white women, Pacific Islander women had higher odds of experiencing preterm birth (OR = 1.40, 95% CI: 1.28-1.53). Four risk factors for preterm birth could be explored with the data available: hypertension, diabetes, smoking, and pre-pregnancy body mass index; hypertension and diabetes significantly increased the odds of preterm birth.

CONCLUSIONS

Existing literature suggests that United States Pacific Islanders were more likely to experience preterm birth than white women, although the pooled prevalence varied by Pacific Islander subgroup. Data support the need for disaggregation of Pacific Islanders in future research and argue for examination of subgroup-specific outcomes to address perinatal health disparities.

Validation of ICD-10-CM Diagnosis Codes for Gestational Age at Birth

BACKGROUND

The International Classification of Diseases , 10th Revision, Clinical Modification (ICD-10-CM) introduced diagnosis codes for week of gestation. Our objective was to assess the validity of these codes among live births, which could have major utility in perinatal research and quality improvement.

METHODS

We used linked birth certificate and patient discharge data from births in California during 2016-2019 (N = 1,843,992). We identified gestational age using Z3A.xx ICD-10-CM diagnosis codes in birthing patient discharge data and compared it with the gold standard of obstetric estimate, as recorded on the birth certificate. We further assessed sensitivity and specificity of gestational age categories (≥37 weeks, <37 weeks, <32 weeks, <28 weeks), given these categories are frequently of interest, and evaluated differences in validity of preterm birth (<37 weeks' gestation) by patient characteristics.

RESULTS

One-million seven-hundred seventy-thousand one-hundred three patients had a gestational age recorded in patient discharge and birth certificate data. When comparing gestational age in patient discharge data with birth certificate data, the concordance correlation coefficient was 0.96 (95% confidence interval [CI] = 0.96, 0.96) and the mean difference between the two measurements was 0.047 weeks (95% CI = 0.046, 0.047 weeks). Ninety-five percent of the differences between the two measurements were between -1.00 week and +1.09 weeks. Sensitivity and specificity were 0.94 to 1.00 for all gestational age categories and were 0.94 to 1.00 for preterm birth across sociodemographic groups.

CONCLUSIONS

We found week-specific gestational age at delivery ICD-10-CM diagnosis codes in patient discharge data to have high validity when compared with the best obstetric estimate on the birth certificate.

Protective Places: the Relationship between Neighborhood Quality and Preterm Births to Black Women in Oakland, California (2007-2011)

Black women have the highest incidence of preterm birth (PTB). Upstream factors, including neighborhood context, may be key drivers of this increased risk. This study assessed the relationship between neighborhood quality, defined by the Healthy Places Index, and PTB among Black women who lived in Oakland, California, and gave birth between 2007 and 2011 (N = 5418 women, N = 107 census tracts). We found that, compared with those living in lower quality neighborhoods, women living in higher quality neighborhoods had 20-38% lower risk of PTB, independent of confounders. Findings have implications for place-based research and interventions to address racial inequities in PTB.

Sexual and/or gender minority disparities in obstetrical and birth outcomes

BACKGROUND

Many sexual and/or gender minority individuals build families through pregnancy and childbirth, but it is unknown whether they experience different clinical outcomes than those who are not sexual and/or gender minority individuals.

OBJECTIVE

To evaluate obstetrical and birth outcomes comparing couples who are likely sexual and/or gender minority patients compared with those who are not likely to be sexual and/or gender minority patients.

STUDY DESIGN

We performed a population-based cohort study of live birth hospitalizations during 2016 to 2019 linked to birth certificates in California. California changed its birth certificate in 2016 to include gender-neutral fields such as "parent giving birth" and "parent not giving birth," with options for each role to specify "mother," "father," or "parent." We classified birthing patients in mother-mother partnerships and those who identified as a father in any partnership as likely sexual and/or gender minority and classified birthing patients in mother-father partnerships as likely not sexual and/or gender minority. We used multivariable modified Poisson regression models to estimate the risk ratios for associations between likely sexual and/or gender minority parental structures and outcomes. The models were adjusted for sociodemographic factors, comorbidities, and multifetal gestation selected by causal diagrams. We replicated the analyses after excluding multifetal gestations.

RESULTS

In the final birthing patient sample, 1,483,119 were mothers with father partners, 2572 were mothers with mother partners, and 498 were fathers with any partner. Compared with birthing patients in mother-father partnerships, birthing patients in mother-mother partnerships experienced significantly higher rates of multifetal gestation (adjusted risk ratio, 3.9; 95% confidence interval, 3.4-4.4), labor induction (adjusted risk ratio, 1.2; 95% confidence interval, 1.1-1.3), postpartum hemorrhage (adjusted risk ratio, 1.4; 95% confidence interval, 1.3-1.6), severe morbidity (adjusted risk ratio, 1.4; 95% confidence interval, 1.2-1.8), and nontransfusion severe morbidity (adjusted risk ratio, 1.4; 95% confidence interval, 1.1-1.9). Severe morbidity was identified following the Centers for Disease Control and Prevention "severe maternal morbidity" index. Gestational diabetes mellitus, hypertensive disorders of pregnancy, cesarean delivery, preterm birth (<37 weeks' gestation), low birthweight (<2500 g), and low Apgar score (<7 at 5 minutes) did not significantly differ in the multivariable analyses. No outcomes significantly differed between father birthing patients in any partnership and birthing patients in mother-father partnerships in either crude or multivariable analyses, though the risk of multifetal gestation was nonsignificantly higher (adjusted risk ratio, 1.5; 95% confidence interval, 0.9-2.7). The adjusted risk ratios for the outcomes were similar after restriction to singleton gestations.

CONCLUSION

Birthing mothers with mother partners experienced disparities in several obstetrical and birth outcomes independent of sociodemographic factors, comorbidities, and multifetal gestation. Birthing fathers in any partnership were not at a significantly elevated risk of any adverse obstetrical or birth outcome considered in this study.

Differences in the association between oral corticosteroids and risk of preterm birth by data source: Reconciling the results

OBJECTIVE

To investigate causes of discrepancies in the association between early pregnancy oral corticosteroid (OCS) use and preterm birth (PTB) risk among women with rheumatoid arthritis (RA) in health care utilization [California Medicaid (Medi-Cal)] and prospective cohort (MotherToBaby Pregnancy Studies) data.

METHODS

Separately, we estimated risk ratios (RR) between OCS exposure before gestational day 140 and PTB risk in Medi-Cal (2007-2013; n=844) and MotherToBaby (2003-2014; n=528) data. We explored differences in socio-economic status, OCS dose distribution, exposure misclassification, and confounding by RA severity across the data sources.

RESULTS

PTB risk in women without OCS's was 17.3% in Medi-Cal and was 9.7% in MotherToBaby. There was no association between OCS and PTB in Medi-Cal (adjusted (a)RR: 1.00 (95% CI: 0.71, 1.42)), and a 1.85-fold (95% CI: 1.20, 2.84) increased PTB risk in MotherToBaby. When restricting each sample to women with a high school degree or less, PTB risk following no OCS exposure was 15.9% in Medi-Cal and 16.7% in MotherToBaby; aRR's were 1.16 (95% CI: 0.74, 1.80) in Medi-Cal and 0.81 (95% CI: 0.25, 2.64) in MotherToBaby. Cumulative OCS dose was higher in MotherToBaby (median: 684 mg) than Medi-Cal (median: 300 mg). OCS dose ≤300 mg was not associated with increased PTB risk. Exposure misclassification and confounding by RA severity were unlikely explanations of differences.

DISCUSSION

Higher baseline PTB risk and lower OCS dose distribution in Medi-Cal may explain the discrepancies. Studies are needed to understand the effects of autoimmune disease severity and under-treatment on PTB risk in low-income populations.

Variations in Maternal Factors and Preterm Birth Risk among Non-Hispanic Black, White, and Mixed-Race Black/White Women in the United States, 2017

OBJECTIVE

This study aims to compare preterm birth (PTB) risk and maternal factors associated with PTB among non-Hispanic White, Black, and mixed-race Black/White women in the United States.

METHODS

In this study, we used U.S. birth certificate data from the 2017 National Vital Statistics System. We included live singleton births to women who self-identified as non-Hispanic White, Black, or mixed-race Black/White. PTB was defined as less than 37 weeks of gestation. We used logistic regression models to estimate the PTB odds ratios for Black and Black/White relative to White women, adjusted for maternal factors. We used logistic regression to estimate associations between PTB and maternal factors in race-stratified models.

RESULTS

The sample included a total of 2,297,076 births in 2017 to White (n = 1,792,257), Black (n = 476,969), and Black/White (n = 27,850) women. The prevalence of PTB varied for Black (11.2%), Black/White (8.2%), and White (6.8%) women. The odds of PTB compared with White differed for Black (odds ratio, 1.51; 95% confidence interval, 1.49-1.53) and Black/White (odds ratio, 1.13; 95% confidence interval, 1.08-1.18) women after adjusting for maternal factors. The odds of PTB associated with maternal sociodemographic, prepregnancy, and gestational factors differed by maternal race.

CONCLUSIONS

Evaluation of PTB risk among White, Black, and Black/White women revealed distinct associations between PTB and maternal factors for Black/White women. This study highlights the need for research assessing the relationships between social risk factors such as colorism and racism and the outcome of PTB, and it provides evidence that may inform more targeted PTB prevention among Black/White and Black women.

Singleton pregnancies conceived with infertility treatments and the risk of neonatal and infant mortality

OBJECTIVES

To examine the risks of neonatal and infant mortality in relation to infertility treatment and to quantify the extent to which preterm delivery mediates this relationship.

DESIGN

Cross-sectional study.

SETTING

United States, 2015-2018.

PATIENT(S)

A total of 14,961,207 pregnancies resulting in a singleton live birth.

INTERVENTION(S)

Any infertility treatment, including assisted reproductive technology and fertility-enhancing drugs.

MAIN OUTCOME MEASURE(S)

Neonatal (<28 days) mortality. The effect measure, risk ratio (RR), and 95% confidence interval (CI) were derived from log-linear Poisson models. A causal mediation analysis of the relationship between infertility treatment and mortality associated with preterm delivery (<37 weeks) was performed. The effects of exposure misclassification and unmeasured confounding biases were assessed.

RESULT(S)

Any infertility treatment was documented in 1.3% (n = 198,986) of pregnancies. Infertility treatment was associated with a 51% increased risk of neonatal mortality (RR 1.51, 95% CI 1.39-1.64), with a slightly higher risk for early neonatal mortality (RR 1.57, 95% CI 1.43-1.73) than late neonatal mortality (RR 1.33, 95% CI 1.11-1.58). These risks were similar for pregnancies conceived through assisted reproductive technology and fertility-enhancing drugs. The mediation analysis showed that 72% (95% CI 59-85) of the total effect of infertility treatment on neonatal mortality was mediated through preterm delivery. In a sensitivity analysis, following corrections for exposure misclassification and unmeasured confounding biases, these risks were higher for early, but not for late, neonatal mortality.

CONCLUSION(S)

Pregnancies conceived with infertility treatment are associated with increased neonatal mortality, and this association is largely mediated through preterm delivery. However, given the substantial underreporting of infertility treatment, these associations must be cautiously interpreted.

Occurrence of fatal police violence during pregnancy and hazard of preterm birth in California

BACKGROUND

Exposure to fatal police violence may play a role in population-level inequities in risk for preterm delivery.

OBJECTIVE

To evaluate whether exposure to fatal police violence during pregnancy affects the hazard of preterm delivery and whether associations differ by race/ethnicity and fetal sex.

METHODS

We leveraged temporal variation in incidents of fatal police violence within census tracts to assess whether occurrence of fatal police violence in a person's tract during pregnancy was associated with increased hazard of extremely (20-27 weeks), early (28-31 weeks), moderate (32-33 weeks), and late (32-36 weeks) preterm delivery in California from 2007 to 2015. We used both death records and the Fatal Encounters database to identify incidents of fatal police violence. We estimated hazard ratios (HR) using time-varying Cox proportional hazard models stratified by census tract, controlling for age, race/ethnicity, educational attainment, health insurance type, parity, and the year and season of conception. We further stratified by race/ethnicity and infant sex to evaluate whether there were differential effects by these characteristics.

RESULTS

Exposure to an incident of fatal police violence was associated with a small increase in the hazard of late preterm birth using both the death records (N = 376,029; hazard ratio [HR] 1.05, 95% confidence interval [CI] 1.00, 1.10) and the Fatal Encounters data (N = 938,814; HR 1.03, 95% CI 1.00, 1.06). We also observed an association for moderate preterm birth in the Fatal Encounters data (HR 1.06, 95% CI 0.98, 1.15). We did not observe associations for early or extremely preterm birth in either data source. Larger relative hazards of moderate (HR 1.25, 95% CI 0.93, 1.68) and late preterm delivery (HR 1.18, 95% CI 1.05, 1.33) were observed among Black birth parents with female births in the Fatal Encounters data.

CONCLUSIONS

Preventing police use of lethal force may reduce preterm delivery in communities where such violence occurs.

Environmental hazards, social inequality, and fetal loss: Implications of live-birth bias for estimation of disparities in birth outcomes

Restricting to live births can induce bias in studies of pregnancy and developmental outcomes, but whether this live-birth bias results in underestimating disparities is unknown. Bias may arise from collider stratification due to an unmeasured common cause of fetal loss and the outcome of interest, or depletion of susceptibles, where exposure differentially causes fetal loss among those with underlying susceptibility.

METHODS

We conducted a simulation study to examine the magnitude of live-birth bias in a population parameterized to resemble one year of conceptions in California (N = 625,000). We simulated exposure to a non-time-varying environmental hazard, risk of spontaneous abortion, and time to live birth using 1000 Monte Carlo simulations. Our outcome of interest was preterm birth. We included a social vulnerability factor to represent social disadvantage, and estimated overall risk differences for exposure and preterm birth using linear probability models and stratified by the social vulnerability factor. We calculated how often confidence intervals included the true point estimate (CI coverage probabilities) to illustrate whether effect estimates differed qualitatively from the truth.

RESULTS

Depletion of susceptibles resulted in a larger magnitude of bias compared with collider stratification, with larger bias among the socially vulnerable group. Coverage probabilities were not adversely affected by bias due to collider stratification. Depletion of susceptibles reduced coverage, especially among the socially vulnerable (coverage among socially vulnerable = 46%, coverage among nonsocially vulnerable = 91% in the most extreme scenario).

CONCLUSIONS

In simulations, hazardous environmental exposures induced live-birth bias and the bias was larger for socially vulnerable women.

Maternal Obesity and the Risk of Early-Onset and Late-Onset Hypertensive Disorders of Pregnancy

OBJECTIVE

To evaluate the relationship between maternal body mass index (BMI) at delivery and rates of early-onset and late-onset hypertensive disorders of pregnancy.

METHODS

We performed a population-based, retrospective cohort study using U.S. Vital Statistics period-linked birth and infant death certificates from 2014 to 2017. Women who delivered a nonanomalous singleton live neonate from 24 to 41 completed weeks of gestation were included. We excluded women with chronic hypertension and those with BMIs less than 18.5. The primary exposure was maternal BMI, defined as nonobese (BMI 18.5-29.9; referent group), class 1 obesity (BMI 30.0-34.9), class 2 obesity (BMI 35.0-39.9), and class 3 obesity (BMI 40.0 or greater). The primary outcome was delivery with hypertensive disorders of pregnancy (gestational hypertension, preeclampsia, or eclampsia) at less than 34 weeks of gestation or at 34 weeks or more. Multivariable Poisson regression was used to estimate relate risk and adjust for confounding variables. Results are presented as adjusted relative risk (aRR) and 95% CIs.

RESULTS

Of the 15.8 million women with live births during the study period, 14.0 million (88.6%) met inclusion criteria, and 825,722 (5.9%) had hypertensive disorders of pregnancy. The risk of early-onset hypertensive disorders of pregnancy was significantly higher in women with class 1 obesity (aRR 1.13; 95% CI 1.10-1.16), class 2 obesity (aRR 1.57; 95% CI 1.53-1.62), and class 3 obesity (aRR 2.18; 95% CI 2.12-2.24), compared with nonobese women. The risk of late-onset hypertensive disorders of pregnancy was also significantly increased in women with class 1 obesity (aRR 1.71; 95% CI 1.70-1.73), class 2 obesity (aRR 2.60; 95% CI 2.58-2.62), and class 3 obesity (aRR 3.93; 95% CI 3.91-3.96) compared with nonobese women.

CONCLUSION

Compared with nonobese women, the risk of early-onset and late-onset hypertensive disorders of pregnancy is significantly and progressively increased among women with increased class of obesity.

Adverse maternal and neonatal outcomes among low-risk women with obesity at 37-41 weeks gestation

OBJECTIVE

To evaluate adverse neonatal and maternal outcomes among women with obesity and no additional comorbidities at 37-41 weeks.

METHODS

This was a population based retrospective cohort study performed using US vital statistics data from 2014-2017. We included women with body mass index ≥ 30.0 kg/m² and a singleton, cephalic, non-anomalous pregnancy who attempted labor and delivered between 37 0/7-41 6/7 weeks. Women with chronic hypertension, gestational diabetes, or pregestational diabetes were excluded. The co-primary outcomes were composite neonatal morbidity (Apgar score < 5 at 5 min, assisted ventilation > 6 h, neonatal seizures, or neonatal death within 27 days) and composite maternal morbidity (admission to the intensive care unit, blood transfusion, uterine rupture, or unplanned hysterectomy) with completed weeks of gestation as the primary exposure variable. All outcomes were examined using multivariate Poisson regression and were reported as adjusted risk ratios (aRR) with 95 % confidence intervals (95 % CI).

RESULTS

There were 15.8 million live births between 2014-2017, of whom 5.1 million (32.1 %) met the inclusion criteria. Composite neonatal morbidity was significantly increased in women delivering at 37 weeks (aRR 1.84; 95 % CI 1.78-1.90), 38 weeks (aRR 1.14; 95 % CI 1.10-1.17), 40 weeks (aRR 1.19; 95 % CI 1.16-1.22), and 41 weeks (aRR 1.49; 95 % CI 1.44-1.53) compared to 39 weeks. Composite maternal morbidity was similarly increased at 37 weeks (aRR 1.26; 95 % CI 1.19-1.34), 38 weeks (aRR 1.07; 95 % CI 1.02-1.13), 40 weeks (aRR 1.16; 95 % CI 1.11-1.20), and 41 weeks (aRR 1.42; 95 % CI 1.34-1.49).

CONCLUSION

Composite neonatal and maternal morbidity among women with obesity and no additional comorbidities is increased with delivery at 37, 38, 40, or 41 weeks compared with 39 weeks.

Exposure to Community Homicide During Pregnancy and Adverse Birth Outcomes: A Within-Community Matched Design

BACKGROUND

Community violence is an understudied aspect of social context that may affect risk of preterm birth and small-for-gestational age (SGA).

METHODS

We matched California mothers with live singleton births who were exposed to a homicide in their Census tract of residence in 2007-2011 to unexposed mothers within the same tract. We estimated risk differences with a weighted linear probability model, with weights corresponding to the matched data structure. We estimated the average treatment effect on the treated of homicide exposure on the risk of preterm birth and SGA during the preconception period and first and second trimester.

RESULTS

We found a small increase in risk of SGA associated with homicide exposure in the first trimester (0.14% [95% confidence interval (CI) = -0.01%, 0.30%]), but not for exposure during the preconception period (-0.01% [95% CI = -0.17%, 0.15%]) or the second trimester (-0.06% [95% CI = -0.23%, 0.11%]). Risk of preterm birth was not affected by homicide exposure. When women were exposed to homicides during all three exposure windows, there was a larger increase in risk of SGA (1.09% [95% CI = 0.15%, 2.03%]) but not preterm birth (0.14% [95% CI = -0.74%, 1.01%]). Exposure to three or more homicides was also associated with greater risk of SGA (0.78% [95% CI = 0.15%, 1.40%]). Negative controls indicated that residual confounding by temporal patterning was unlikely.

CONCLUSIONS

Homicide exposure during early pregnancy is associated with a small increased risk of SGA.

Associations between green space and preterm birth: Windows of susceptibility and interaction with air pollution

BACKGROUND

Recent studies have reported inconsistent associations between maternal residential green space and preterm birth (PTB, born < 37 completed gestational weeks). In addition, windows of susceptibility during pregnancy have not been explored and potential interactions of green space with air pollution exposures during pregnancy are still unclear.

OBJECTIVES

To evaluate the relationships between green space and PTB, identify windows of susceptibility, and explore potential interactions between green space and air pollution.

METHODS

Birth certificate records for all births in California (2001-2008) were obtained. The Normalized Difference Vegetation Index (NDVI) was used to characterized green space exposure. Gestational age was treated as a time-to-event outcome; Cox proportional hazard models were applied to estimate the association between green space exposure and PTB, moderately PTB (MPTB, gestational age < 35 weeks), and very PTB (VPTB, gestational age < 30 weeks), after controlling for maternal age, race/ethnicity, education, and median household income. Month-specific green space exposure was used to identify potential windows of susceptibility. Potential interactions between green space and air pollution [fine particulate matter < 2.5 µm (PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃)] were examined on both additive and multiplicative scales.

RESULTS

In total, 3,753,799 eligible births were identified, including 341,123 (9.09%) PTBs, 124,631 (3.32%) MPTBs, and 22,313 (0.59%) VPTBs. A reduced risk of PTB was associated with increases in residential NDVI exposure in 250 m, 500 m, 1000 m, and 2000 m buffers. In the 2000 m buffer, the association was strongest for VPTB [adjusted hazard ratio (HR) per interquartile range increase in NDVI: 0.959, 95% confidence interval (CI): 0.942-0.976)], followed by MPTB (HR = 0.970, 95% CI: 0.962-0.978) and overall PTB (HR = 0.972, 95% CI: 0.966-0.978). For PTB, green space during the 3rd - 5th gestational months had stronger associations than those in the other time periods, especially during the 4th gestational month (NDVI 2000 m: HR = 0.970, 95% CI: 0.965-0.975). We identified consistent positive additive and multiplicative interactions between decreasing green space and higher air pollution.

CONCLUSION

This large study found that maternal exposure to residential green space was associated with decreased risk of PTB, MPTB, and VPTB, especially in the second trimester. There is a synergistic effect between low green space and high air pollution levels on PTB, indicating that increasing exposure to green space may be more beneficial for women with higher air pollution exposures during pregnancy.

Oral Corticosteroids and Risk of Preterm Birth in the California Medicaid Program

BACKGROUND

There is limited information regarding the impact of dose and gestational timing of oral corticosteroid (OCS) use on preterm birth (PTB), especially among women with asthma.

OBJECTIVES

To evaluate OCS dose and timing on PTB for asthma and, as a comparison, systemic lupus erythematosus (SLE).

METHODS

We used health care data from California Medicaid enrollees linked to birth certificates (2007-2013), identifying women with asthma (n = 22,084) and SLE (n = 1174). We estimated risk ratios (RR) for OCS cumulative dose trajectories and other disease-related medications before gestational day 140 and hazard ratios (HR) for time-varying exposures after day 139.

RESULTS

For asthma, PTB risk was 14.0% for no OCS exposure and 14.3%, 16.8%, 20.5%, and 32.7% in low, medium, medium-high, and high cumulative dose trajectory groups, respectively, during the first 139 days. The high-dose group remained associated with PTB after adjustment (adjusted RR [aRR]: 1.46; 95% confidence interval [CI]: 1.00, 2.15). OCS dose after day 139 was not clearly associated with PTB, nor were controller medications. For SLE, PTB risk for no OCS exposure was 24.9%, and it was 39.1% in low- and 61.2% in high-dose trajectory groups. aRR were 1.80 (95% CI: 1.34, 2.40) for high and 1.24 (95% CI: 0.97, 1.58) for low groups. Only prednisone equivalent dose >20 mg/day after day 139 was associated with increased PTB (adjusted HR: 2.54; 95% CI: 1.60, 4.03).

CONCLUSIONS

For asthma, higher OCS doses early in pregnancy, but not later, were associated with increased PTB. For SLE, higher doses early and later in pregnancy were associated with PTB.

Neighborhood Privilege, Preterm Delivery, and Related Racial/Ethnic Disparities: An Intergenerational Application of the Index of Concentration at the Extremes

We assessed whether early childhood and adulthood experiences of neighborhood privilege, measured by the Index of Concentration at the Extremes (ICE), were associated with preterm delivery and related racial/ethnic disparities using intergenerationally linked birth records of 379,794 California-born primiparous mothers (born 1982-1997) and their infants (born 1997-2011). ICE measures during early childhood and adulthood approximated racial/ethnic and economic dimensions of neighborhood privilege and disadvantage separately (ICE-income, ICE-race/ethnicity) and in combination (ICE-income + race/ethnicity). Results of our generalized estimating equation models with robust standard errors showed associations for ICE-income and ICE-income + race/ethnicity. For example, ICE-income + race/ethnicity was associated with preterm delivery in both early childhood (relative risk (RR) = 1.12, 95% confidence interval (CI): 1.08, 1.17) and adulthood (RR = 1.07, 95% CI: 1.03, 1.11). Non-Hispanic black and Hispanic women had higher risk of preterm delivery than white women (RR = 1.32, 95% CI: 1.28, 1.37; and RR = 1.11, 95% CI: 1.08, 1.14, respectively, adjusting for individual-level confounders). Adjustment for ICE-income + race/ethnicity at both time periods yielded the greatest declines in disparities (for non-Hispanic black women, RR = 1.23, 95% CI: 1.18, 1.28; for Hispanic women, RR = 1.05, 95% CI: 1.02, 1.09). Findings support independent effects of early childhood and adulthood neighborhood privilege on preterm delivery and related disparities.

Early pregnancy prediction of gestational diabetes mellitus risk using prenatal screening biomarkers in nulliparous women

AIMS

To evaluate the clinical utility of first and second trimester prenatal screening biomarkers for early pregnancy prediction of gestational diabetes mellitus (GDM) risk in nulliparous women.

METHODS

We conducted a population-based cohort study of nulliparous women participating in the California Prenatal Screening Program from 2009 to 2011 (n = 105,379). GDM was ascertained from hospital discharge records or birth certificates. Models including maternal characteristics and prenatal screening biomarkers were developed and validated. Risk stratification and reclassification were performed to assess clinical utility of the biomarkers.

RESULTS

Decreased levels of first trimester pregnancy-associated plasma protein A (PAPP-A) and increased levels of second trimester unconjugated estriol (uE₃) and dimeric inhibin A (INH) were associated with GDM. The addition of PAPP-A only and PAPP-A, uE₃, and INH to maternal characteristics resulted in small, yet significant, increases in area under the receiver operating characteristic curve (AUC) (maternal characteristics only: AUC 0.714 (95% CI 0.703-0.724), maternal characteristics + PAPP-A: AUC 0.718 (95% CI 0.707-0.728), maternal characteristics + PAPP-A, uE₃, and INH: AUC 0.722 (0.712-0.733)); however, no net improvement in classification was observed.

CONCLUSIONS

PAPP-A, uE₃, and INH have limited clinical utility for prediction of GDM risk in nulliparous women. Utility of other readily accessible clinical biomarkers in predicting GDM risk warrants further investigation.

Relationships between greenness and low birth weight: Investigating the interaction and mediation effects of air pollution

BACKGROUND

Associations between residential greenness and improved birth weight have been increasingly reported, but underlying mechanisms and interactions with other environmental exposures are still unclear.

OBJECTIVES

To study the relationships between low birth weight (LBW, <2500 g), residential greenness, and the potential influence of air pollution in these relationships (interaction and mediation) in California, over the period 2001-2008.

METHODS

Residential greenness around maternal homes was characterized using the Normalized Difference Vegetation Index (NDVI). Complementary indicators of air pollution exposure reflected its main components. Birth weight and maternal characteristics were obtained from birth certificate records. In this case-cohort study, associations between greenness and LBW were investigated using multi-level Poisson regression with random effect at the hospital level. We investigated potential interaction of greenness and air pollutants on both additive and multiplicative scales. Mediation analyses were conducted to estimate the potential contribution of local variations in air pollutant concentrations associated with greenness on LBW risk.

RESULTS

In total 72,632 LBW cases were included. A reduction of LBW risk was associated with an increase in NDVI (adjusted risk ratio per inter-quartile range in NDVI: 0.963; 95% confidence interval: 0.947; 0.978). We observed no interaction between NDVI and air pollution on LBW risk. The estimated mediating effect of fine particulate matter in the impact of greenness on LBW was 12%.

CONCLUSION

This large study confirms that residential greenness is associated with a reduced risk of LBW and suggests that greenness might benefit to LBW partly through a local reduction in air pollution.

Previous Adverse Outcome of Term Pregnancy and Risk of Preterm Birth in Subsequent Pregnancy

Objective Evaluate risk of preterm birth (PTB, < 37 completed weeks' gestation) among a population of women in their second pregnancy with previous full term birth but other adverse pregnancy outcome. Methods The sample included singleton live born infants between 2007 and 2012 in a birth cohort file maintained by the California Office of Statewide Health Planning and Development. The sample was restricted to women with two pregnancies resulting in live born infants and first birth between 39 and 42 weeks' gestation. Logistic regression was used to calculate the risk of PTB in the second birth for women with previous adverse pregnancy outcome including: small for gestational age (SGA) infant, preeclampsia, placental abruption, or neonatal death (≤ 28 days). Risks were adjusted for maternal factors recorded for second birth. Results The sample included 133,622 women. Of the women with any previous adverse outcome, 4.7% had a PTB while just 3.0% of the women without a previous adverse outcome delivered early (relative risk adjusted for maternal factors known at delivery 1.4, 95% CI 1.3-1.5). History of an SGA infant, placental abruption, or neonatal death increased the adjusted risk of PTB in their second birth by 1.5-3.7-fold. History of preeclampsia did not elevate the risk of a preterm birth in the subsequent birth. Conclusions for Practice The findings indicate that women with previous SGA infant, placental abruption, or neonatal death, despite a term delivery, may be at increased risk of PTB in the subsequent birth. These women may be appropriate participates for future interventions aimed at reduction in PTB.

Examining interpregnancy intervals and maternal and perinatal health outcomes using U.S. vital records: Important considerations for analysis and interpretation

BACKGROUND

Numerous studies use birth certificate data to examine the association between interpregnancy interval (IPI) and maternal and perinatal health outcomes. Substantive changes from the latest birth certificate revision have implications for examining this relationship.

METHODS

We provide an overview of the National Vital Statistics System and recent changes to the national birth certificate data file, which have implications for assessing IPI and perinatal health outcomes. We describe the calculation of IPI using birth certificate information and related measurement issues. Missing IPI values by maternal age, race and education using 2016 birth certificate data were also compared. Finally, we review and summarise data quality studies of select covariate and outcome variables (sociodemographic, maternal health and health behaviours, and infant health) conducted after the most recent 2003 birth certificate revision.

RESULTS

Substantive changes to data collection, dissemination and quality have occurred since the 2003 revision. These changes impact IPI measurement, trends and associations with perinatal health outcomes. Missing values of IPI were highest for older ages, lower education and non-Hispanic black women. Minimal differences were found when comparing IPI using different gestational age measures. Recent data quality studies pointed to substantial variation in data quality by item and across states.

CONCLUSION

Future studies examining the association of IPI with maternal and perinatal data using vital records should consider these aspects of the data in their research plan, sensitivity analyses and interpretation of findings.

Prevalence and descriptive epidemiology of infantile hypertrophic pyloric stenosis in the United States: A multistate, population-based retrospective study, 1999-2010

BACKGROUND

Antecedents for infantile hypertrophic pyloric stenosis (IHPS) vary across studies; therefore, we conducted a multistate, population-based retrospective study of the prevalence and descriptive epidemiology of IHPS in the United States (US).

METHODS

Data for IHPS cases (n = 29,554) delivered from 1999-2010 and enumerated from 11 US population-based birth defect surveillance programs, along with data for live births (n = 14,707,418) delivered within the same birth period and jurisdictions, were analyzed using Poisson regression to estimate IHPS prevalence per 10,000 live births. Additional data on deliveries from 1999-2005 from seven of these programs were analyzed using multivariable logistic regression to estimate adjusted prevalence ratios (aPR)s and 95% confidence intervals (CI)s for selected infant and parental characteristics.

RESULTS

Overall, IHPS prevalence from 1999-2010 was 20.09 (95% CI = 19.87, 20.32) per 10,000 live births, with statistically significant increases from 2003-2006 and decreases from 2007-2010. Compared to their respective referents, aPRs were higher in magnitude for males, preterm births, and multiple births, but lower for birth weights <2,500 g. The aPRs for all cases increased with decreasing parental age, maternal education, and maternal parity, but decreased for parental race/ethnicity other than non-Hispanic White. Estimates restricted to isolated cases or stratified by infant sex were similar to those for all cases.

CONCLUSIONS

This study covers one of the largest samples and longest temporal period examined for IHPS in the US. Similar to findings reported in Europe, estimates suggest that IHPS prevalence has decreased recently in the US. Additional analyses supported associations with several infant and parental characteristics.

Life-course neighbourhood opportunity and racial-ethnic disparities in risk of preterm birth

BACKGROUND

Neighbourhood opportunity, measured by poverty, income and deprivation, has been associated with preterm birth, however little is known about the contribution of early-life and life-course neighbourhood opportunity to preterm birth risk and racial-ethnic disparities. We examined maternal early-life and adult neighbourhood opportunity in relation to risk of preterm birth and racial-ethnic disparities in a population-based cohort of women under age 30.

METHODS

We linked census tract poverty data to 2 generations of California births from 1982-2011 for 403 315 white, black, or Latina mothers-infant pairs. We estimated the risk of preterm birth, and risk difference (RD) comparing low opportunity (≥20% poverty) in early life or adulthood to high opportunity using targeted maximum likelihood estimation.

RESULTS

At each time point, low opportunity was related to increased preterm birth risk compared to higher opportunity neighbourhoods for white, black and Latina mothers (RDs 0.3-0.7%). Compared to high opportunity at both time points, risk differences were generally highest for sustained low opportunity (RD 1.5, 1.3, and 0.7% for white, black and Latina mothers, respectively); risk was elevated with downward mobility (RD 0.7, 1.3, and 0.4% for white, black and Latina mothers, respectively), and with upward mobility only among black mothers (RD 1.2%). The black-white preterm birth disparity was reduced by 22% under high life-course opportunity.

CONCLUSIONS

Early-life and sustained exposure to residential poverty is related to increased PTB risk, particularly among black women, and may partially explain persistent black-white disparities.

Prematurity and Sudden Unexpected Infant Deaths in the United States

BACKGROUND AND OBJECTIVES

Prematurity, a strong risk factor for sudden unexpected infant death (SUID), was addressed in recommendations by the American Academy of Pediatrics in 2011 for safe sleep education in NICUs. We documented associations between gestational age (GA) and SUID subsequent to these guidelines.

METHODS

Using the 2012-2013 US linked infant birth and death certificate period files, we documented rates per live births of sudden infant death syndrome, ill-defined and unspecified causes, accidental suffocation and strangulation in bed, and overall SUID by GA in postneonatal, out-of-hospital, and autopsied cases; compared survivors and cases; and estimated logistic regression models of associations between GA and SUID.

RESULTS

SUID cases were more likely than survivors to be <37 weeks' GA (22.61% vs 10.79%; P < .0001). SUID rates were 2.68, 1.94, 1.46, 1.16, 0.73, and 0.51 per 1000 live births for 24 to 27, 28 to 31, 32 to 33, 34 to 36, 37 to 38, and 39 to 42 weeks' GA, respectively. Logistic regression models additionally indicated declines in the risk for SUID as GA increased. Prenatal smoking, inadequate prenatal care, and demographics associated with poverty were strongly associated with SUID.

CONCLUSIONS

Despite the 2011 American Academy of Pediatrics recommendations for increased safe sleep education in the NICUs, SUID rates were inversely associated with GA in 2012 to 2013, suggesting that risk of SUID associated with prematurity has multiple etiologies requiring continued investigation, including biological vulnerabilities and the efficacy of NICU education programs, and that strategies to reduce SUID should be multifaceted.

Infant Outcomes After Elective Early-Term Delivery Compared With Expectant Management

OBJECTIVE

To compare the risk of neonatal morbidity and infant mortality between elective early-term deliveries and those expectantly managed and delivered at 39 weeks of gestation or greater.

METHODS

We conducted a population-based retrospective cohort study of 675,302 singleton infants born alive at 37-44 weeks of gestation from 2005 to 2009 in more than 125 birthing facilities in Florida. Data were collected from a validated, longitudinally linked maternal and infant database. The study population was categorized into exposure groups based on the timing and reason for delivery initiation-four subtypes of deliveries at 37-38 weeks of gestation and a comparison group of expectantly managed infants delivered at 39-40 weeks of gestation. Primary outcomes included neonatal respiratory morbidity, sepsis, feeding difficulties, admission to the neonatal intensive care unit (NICU), and infant mortality.

RESULTS

Neonatal outcome rates ranged from 6.0% for respiratory morbidities to 1.3% for both sepsis and feeding difficulties, and the infant mortality rate was 1.5 per 1,000 live births. When compared with infants expectantly managed and delivered at 39-40 weeks of gestation, those delivered after elective induction at 37-38 weeks of gestation did not have increased odds of neonatal respiratory morbidity, sepsis, or NICU admission but did experience slightly higher odds of feeding difficulty (odds ratio 1.18, 99% confidence interval 1.02-1.36). In contrast, infants delivered by elective cesarean at 37-38 weeks of gestation had 13-66% increased odds of adverse outcomes. Survival experiences were similar when comparing early inductions and early cesarean deliveries with the expectant management group.

CONCLUSION

The issues that surround the timing and reasons for delivery initiation are complicated and each pregnancy unique. This study cautions against a general avoidance of all elective early-term deliveries.

Predicting Preterm Birth Among Women Screened by North Carolina's Pregnancy Medical Home Program

OBJECTIVE

To determine which combination of risk factors from Community Care of North Carolina's (CCNC) Pregnancy Medical Home (PMH) risk screening form was most predictive of preterm birth (PTB) by parity and race/ethnicity.

METHODS

This retrospective cohort included pregnant Medicaid patients screened by the PMH program before 24 weeks gestation who delivered a live birth in North Carolina between September 2011-September 2012 (N = 15,428). Data came from CCNC's Case Management Information System, Medicaid claims, and birth certificates. Logistic regression with backward stepwise elimination was used to arrive at the final models. To internally validate the predictive model, we used bootstrapping techniques.

RESULTS

The prevalence of PTB was 11 %. Multifetal gestation, a previous PTB, cervical insufficiency, diabetes, renal disease, and hypertension were the strongest risk factors with odds ratios ranging from 2.34 to 10.78. Non-Hispanic black race, underweight, smoking during pregnancy, asthma, other chronic conditions, nulliparity, and a history of a low birth weight infant or fetal death/second trimester loss were additional predictors in the final predictive model. About half of the risk factors prioritized by the PMH program remained in our final model (ROC = 0.66). The odds of PTB associated with food insecurity and obesity differed by parity. The influence of unsafe or unstable housing and short interpregnancy interval on PTB differed by race/ethnicity.

CONCLUSIONS

Evaluation of the PMH risk screen provides insight to ensure women at highest risk are prioritized for care management. Using multiple data sources, salient risk factors for PTB were identified, allowing for better-targeted approaches for PTB prevention.

The association between temporal changes in the use of obstetrical intervention and small-for-gestational age live births

BACKGROUND

The literature attributes secular declines in small-for-gestational age (SGA) live births to changes in maternal smoking and other maternal characteristics. However, there are reasons to believe that the observed reductions in SGA may be a consequence of early delivery following obstetric intervention.

METHODS

We examined temporal trends in obstetrical intervention and SGA among singleton live births in the United States from 1990 to 2010. The modified Kitagawa decomposition, based on the fetuses-at-risk approach, was used to assess the relative contribution of changes in the gestational age distribution and gestational age-specific SGA to overall changes in SGA. Reductions in SGA rates due to a left shift in the gestational age distribution were assumed to primarily reflect increased obstetrical intervention, whereas decreases in overall SGA due to decreases in gestational-age-specific SGA rates were assumed to reflect declines in risk factors.

RESULTS

Temporal trends in SGA followed a non-linear pattern, with substantial declines from 10.1% in 1990-92 to 8.9% in 2002-04, followed by a small increase to 9.1% in 2008-10. Rates of maternal smoking steadily decreased throughout the same time period and changes in SGA rates were more consistent with changes in the gestational age distribution. The modified Kitagawa decomposition analysis also attributed the initial decline in SGA rates to changes in the gestational age distribution.

CONCLUSIONS

Complex temporal pattern in SGA rates cannot be explained by the linear pattern of changes in factors like maternal smoking. Changes in the gestational age distribution are more consistent with the observed secular trends in SGA rates.

Validation of selected items on the 2003 U.S. standard certificate of live birth: New York City and Vermont

OBJECTIVE

We assessed the validity of selected items on the 2003 revised U.S. Standard Certificate of Live Birth to understand the accuracy of new and existing items.

METHODS

We calculated sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of select variables reported on the birth certificate using the medical record as the gold standard for a representative sample of live births in New York City (n=603) and Vermont (n=664) in 2009.

RESULTS

In both sites, sensitivity was excellent (>90%) for Medicaid coverage at delivery, any previous live births, and current method of delivery; sensitivity was moderate (70%-90%) for gestational diabetes; and sensitivity was poor (<70%) for premature rupture of the membranes and gestational hypertension. In both sites, PPV was excellent for Medicaid coverage, any previous live births, previous cesarean delivery, and current method of delivery, and poor for premature rupture of membranes. In both sites, almost all items had excellent (>90%) specificity and NPV.

CONCLUSION

Further research is needed to determine how best to improve the quality of data on the birth certificate. Future revisions of the birth certificate may consider removing those items that have consistently proven difficult to report accurately.

Fighting for the next generation: US Prematurity in 2030

Preterm birth (PTB) is a serious problem, with >450 000 neonates born prematurely in the United States every year. Beginning in 1980, the United States experienced a nearly 3-decade rise in the PTB rate, peaking in 2006 at 12.8%. PTB has declined for 7 consecutive years to 11.4% in 2013, but it still accounts for 1 in 9 neonates born every year. In addition to elevated neonatal and infant mortality among those born preterm, many who survive will have lifelong morbidities and disabilities. Because of the burden of morbidity, disability, and mortality for PTB, as well as its impact more broadly on society, including excess annual costs estimated to be at least $26.2 billion by a committee for the Institute of Medicine, the March of Dimes initiated the Prematurity Campaign in 2003. In 2008 the March of Dimes established a goal of reducing the US PTB rate to 9.6% by 2020. However, the United States ranks extremely poorly for PTB rates among Very High Human Development Index (VHHDI) countries, subjecting untold numbers of neonates to unnecessary morbidity and mortality. Therefore, the March of Dimes proposes an aspirational goal of 5.5% for the 2030 US PTB rate, which would put the United States in the top 4 (10%) of 39 VHHDI countries. This 5.5% PTB rate is being achieved in VHHDI countries and by women from diverse settings receiving optimal care. This goal can be reached and will ensure a better start in life for many more neonates in the next generation.

Validation of obstetric estimate of gestational age on US birth certificates

OBJECTIVE

The birth certificate variable obstetric estimate of gestational age (GA) has not been previously validated against GA based on estimated date of delivery from medical records.

STUDY DESIGN

We estimated sensitivity, specificity, positive predictive value, negative predictive value and the corresponding 95% confidence intervals (CIs) for preterm delivery (<37 weeks' gestation) based on obstetric estimate using estimated date of delivery-based GA as the gold standard. Trained abstractors obtained the estimated date of delivery from the prenatal record (64.8% in New York City, and 94.6% in Vermont), or, when not available, from the hospital delivery record for 2 population-based samples: 586 live births delivered in New York City and 649 live births delivered in Vermont during 2009. Weights were applied to account for nonresponse and sampling design.

RESULTS

In New York City, the preterm delivery rate based on estimated date of delivery was 9.7% (95% CI, 7.6-12.4) and 8.2% (95% CI, 6.3-10.6) based on obstetric estimate; in Vermont, it was 6.8% (95% CI, 5.4-8.4) based on estimated date of delivery and 6.3% (95% CI, 5.1-7.8) based on obstetric estimate. In New York City, sensitivity of obstetric estimate-based preterm delivery was 82.5% (95% CI, 69.4-90.8), specificity 98.1% (95% CI, 96.4-99.1), positive predictive value 98.0% (95% CI, 95.2-99.2), and negative predictive value 98.8% (95% CI, 99.6-99.9). In Vermont, sensitivity of obstetric estimate-based preterm delivery was 93.8% (95% CI, 81.8-98.1), specificity 99.6% (95% CI, 98.5-99.9), positive predictive value 100%, and negative predictive value 100%.

CONCLUSION

Obstetric estimate-based preterm delivery had excellent specificity, positive predictive value and negative predictive value. Sensitivity was moderate in New York City and excellent in Vermont. These results suggest obstetric estimate-based preterm delivery from the birth certificate is useful for the surveillance of preterm delivery.