Comparative accuracy of clinical estimate versus menstrual gestational age in computerized birth certificates

Working with what you have: How the East Africa Preterm Birth Initiative used gestational age data from facility maternity registers

Objective

Preterm birth is the primary driver of neonatal mortality worldwide, but it is defined by gestational age (GA) which is challenging to accurately assess in low-resource settings. In a commitment to reducing preterm birth while reinforcing and strengthening facility data sources, the East Africa Preterm Birth Initiative (PTBi-EA) chose eligibility criteria that combined GA and birth weight. This analysis evaluated the quality of the GA data as recorded in maternity registers in PTBi-EA study facilities and the strength of the PTBi-EA eligibility criteria.

Methods

We conducted a retrospective analysis of maternity register data from March–September 2016. GA data from 23 study facilities in Migori, Kenya and the Busoga Region of Uganda were evaluated for completeness (variable present), consistency (recorded versus calculated GA), and plausibility (falling within the 3^rd and 97^th birth weight percentiles for GA of the INTERGROWTH-21^st Newborn Birth Weight Standards). Preterm birth rates were calculated using: 1) recorded GA <37 weeks, 2) recorded GA <37 weeks, excluding implausible GAs, 3) birth weight <2500g, and 4) PTBi-EA eligibility criteria of <2500g and between 2500g and 3000g if the recorded GA is <37 weeks.

Results

In both countries, GA was the least recorded variable in the maternity register (77.6%). Recorded and calculated GA (Kenya only) were consistent in 29.5% of births. Implausible GAs accounted for 11.7% of births. The four preterm birth rates were 1) 14.5%, 2) 10.6%, 3) 9.6%, 4) 13.4%.

Conclusions

Maternity register GA data presented quality concerns in PTBi-EA study sites. The PTBi-EA eligibility criteria of <2500g and between 2500g and 3000g if the recorded GA is <37 weeks accommodated these concerns by using both birth weight and GA, balancing issues of accuracy and completeness with practical applicability.

Methodological Issues in the Study of the Development of Pain Responsivity in Preterm Neonates: A Systematic Review

The study of the development of neonatal pain responses is of key importance, both for research and for clinical reasons, with particular regard to the population of preterm neonates, given the amount of painful procedures they are exposed to on a daily basis. The aim of this work was to systematize our knowledge about the development of pain responses in prematurely born neonates by focusing on some key methodological issues. Studies on the impact of age variables, namely gestational age (GA), postmenstrual age (PMA) and chronological age (CH), on pain responsivity in premature neonates were identified using Medline and Scopus. Studies (N = 42) were categorized based on terminological and methodological approaches towards age variables, and according to output variables considered (facial, nonfacial behavioral, physiological). Distinct multidimensional developmental patterns were found for each age-sampling strategy. Overall, each of the three age variables seems to affect pain responsivity, possibly differently across age windows. Targeted as well as integrated approaches, together with a renewed attention for methodological consistency, are needed to further our knowledge on this topic.

Elective Deliveries and Neonatal Outcomes in Full-Term Pregnancies

Cesarean and induced delivery rates have risen substantially in recent decades and currently account for over one-third and one-fourth of US births, respectively. Initiatives to encourage delaying deliveries until a gestational age of 39 weeks appear to have slowed the increases but have not led to declines. The rates are at historic highs and the consequences of these interventions when not medically necessary have not been systematically explored at the population level. In this study, we used population-level data on births in New Jersey (1997-2011) to document trends in elective deliveries (induced vaginal delivery, cesarean delivery with no labor trial, and cesarean delivery after induction) and estimate logistic and linear regression models of associations between delivery method and neonatal morbidities and cost-related outcomes in low-risk pregnancies. We found that elective deliveries more than doubled during the observation period and were associated with neonatal morbidities and cost-related outcomes even at gestational ages of 39 and 40 weeks. Findings suggest that delaying beyond 39 weeks and avoiding delivery interventions when not medically necessary would improve infant health and reduce health-care costs.

Impacts of gestational age uncertainty in estimating associations between preterm birth and ambient air pollution

Supplemental Digital Content is available in the text.

Background:

Previous epidemiologic studies utilizing birth records have shown heterogeneous associations between air pollution exposure during pregnancy and the risk of preterm birth (PTB, gestational age <37 weeks). Uncertainty in gestational age at birth may contribute to this heterogeneity.

Methods:

We first examined disagreement between clinical and last menstrual period-based (LMP) determination of PTB from individual-level birth certificate data for the 20-county Atlanta metropolitan area during 2002 to 2006. We then estimated associations between five trimester-averaged pollutant exposures and PTB, defined using various methods based on the clinical or LMP gestational age. Finally, using a multiple imputation approach, we incorporated uncertainty in gestational age to quantify the impact of this variability on associations between pollutant exposures and PTB.

Results:

Odds ratios (OR) were most elevated when a more stringent definition of PTB was used. For example, defining PTB only when LMP and clinical diagnoses agree yielded an OR of 1.09 (95% confidence interval [CI] = 1.04, 1.14) per interquartile range increase in first trimester carbon monoxide exposure versus an OR of 1.04 (95% CI = 1.01, 1.08) when PTB was defined as either an LMP or clinical diagnosis. Accounting for outcome uncertainty resulted in wider CIs—between 7.4% and 43.8% wider than those assuming the PTB outcome is without error.

Conclusions:

Despite discrepancies in PTB derived using either the clinical or LMP gestational age estimates, our analyses demonstrated robust positive associations between PTB and ambient air pollution exposures even when gestational age uncertainty is present.

Estimation of Day-Specific Probabilities of Conception during Natural Cycle in Women from Babylon

BACKGROUND

Identifying predictors of the probabilities of conception related to the timing and frequency of intercourse in the menstrual cycle is essential for couples attempting pregnancy, users of natural family planning methods, and clinicians diagnosing for possible causes of infertility. The aim of this study is to estimate the days in which the likelihood of conception happened by using first trimester ultrasound fetal biometry in natural cycles and spontaneous pregnancy, and to explore some factors that may affect them.

MATERIALS AND METHODS

This study is retrospective cohort study, with random sampling. It involved 60 pregnant ladies at first trimester; the date of conception was estimated using: i. Crown-rump length biometry (routine ultrasound examinations were performed at a median of 70 days following Last menstrual period or equivalently 10 weeks), ii. Date of last menstrual cycle. Only women with previous infertility and now conceiving naturally with a certain date of Last menstrual period were selected.

RESULTS

The distribution of conception showed a sharp rise from day 8 onwards, reaching its maximum at day 13 and decreasing to zero by day 30 of Last menstrual period. The older and obese women had conceive earlier than younger women but there was insignificants difference between the two groups (P>0.05). According to the type of infertility, the women with secondary infertility had conceived earlier than those with primary infertility. There was a significant difference between the two groups (P<0.05).

CONCLUSION

Day specific of conception may be affected by factors such as age, BMI, and type of infertility. This may be confirmed by larger sample size in metacentric study.

Recurrence of Preterm Birth and Early Term Birth

OBJECTIVE

To examine recurrent preterm birth and early term birth in women's initial and immediately subsequent pregnancies.

METHODS

This retrospective cohort study included 163,889 women who delivered their first and second liveborn singleton neonates between 20 and 44 weeks of gestation in California from 2005 through 2011. Data from hospital discharge records and birth certificates were used for analyses. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression models adjusted for risk factors.

RESULTS

Shorter gestational duration in the first pregnancy increased the risk of subsequent preterm birth (both early, before 32 weeks of gestation, and later, from 32 to 36 weeks of gestation) as well as early term birth (37-38 weeks of gestation). Compared with women with a prior term birth, women with a prior early preterm birth (before 32 weeks of gestation) were at the highest risk for a subsequent early preterm birth (58/935 [6.2%] compared with 367/118,505 [0.3%], adjusted OR 23.3, 95% CI 17.2-31.7). Women with a prior early term birth had more than a twofold increased risk for subsequent preterm birth (before 32 weeks of gestation: 171/36,017 [0.5%], adjusted OR 2.0, 95% CI 1.6-2.3; from 32 to 36 weeks of gestation: 2,086/36,017 [6.8%], adjusted OR 3.0, 95% CI 2.9-3.2) or early term birth (13,582/36,017 [37.7%], adjusted OR 2.2, 95% CI 2.2-2.3).

CONCLUSION

Both preterm birth and early term birth are associated with these outcomes in a subsequent pregnancy. Increased clinical attention and research efforts may benefit from a focus on women with a prior early term birth as well as those with prior preterm birth.

Risk of Preterm or Small-for-Gestational-Age Birth After Influenza Vaccination During Pregnancy: Caveats When Conducting Retrospective Observational Studies

Vaccines are increasingly targeted toward women of reproductive age, and vaccines to prevent influenza and pertussis are recommended during pregnancy. Prelicensure clinical trials typically have not included pregnant women, and when they are included, trials cannot detect rare events. Thus, postmarketing vaccine safety assessments are necessary. However, analysis of observational data requires detailed assessment of potential biases. Using data from 8 Vaccine Safety Datalink sites in the United States, we analyzed the association of monovalent H1N1 influenza vaccine (MIV) during pregnancy with preterm birth (<37 weeks) and small-for-gestational-age birth (birth weight < 10th percentile). The cohort included 46,549 pregnancies during 2009-2010 (40% of participants received the MIV). We found potential biases in the vaccine-birth outcome association that might occur due to variable access to vaccines, the time-dependent nature of exposure to vaccination within pregnancy (immortal time bias), and confounding from baseline differences between vaccinated and unvaccinated women. We found a strong protective effect of vaccination on preterm birth (relative risk = 0.79, 95% confidence interval: 0.74, 0.85) when we ignored potential biases and no effect when accounted for them (relative risk = 0.91; 95% confidence interval: 0.83, 1.0). In contrast, we found no important biases in the association of MIV with small-for-gestational-age birth. Investigators conducting studies to evaluate birth outcomes after maternal vaccination should use statistical approaches to minimize potential biases.

Preterm birth among the Hmong, other Asian subgroups and non-Hispanic whites in California

BACKGROUND

We investigated very preterm (VPTB) and preterm birth (PTB) risk among Hmong women relative to non-Hispanic whites and other Asian subgroups. We also examined the maternal education health gradient across subgroups.

METHODS

California birth record data (2002-2004) were used to analyze 568,652 singleton births to white and Asian women. Pearson Chi-square and logistic regression were used to assess variation in maternal characteristics and VPTB/PTB risk by subgroup.

RESULTS

White, Chinese, Japanese, Korean, Asian Indian, and Vietnamese women had 36-59% lower odds of VPTB and 30-56% lower odds of PTB than Hmong women. Controls for covariates did not substantially diminish these disparities. Cambodian, Filipino and Lao/Thai women's odds of VPTB were similar to that of Hmong women. But they had higher adjusted odds of PTB compared to the Hmong. There was heterogeneity in the educational gradient of PTB, with significant differences between the least and most educated women among whites, Chinese, Japanese, Asian Indians, Cambodians, and Laoians/Thais. Maternal education was not associated with PTB for Hmong, Vietnamese and Korean women, however.

CONCLUSIONS

Studies of Hmong infant health from the 1980s, the decade immediately following the group's mass migration to the US, found no significant differences in adverse birth outcomes between Hmong and white women. By the early 2000s, however, the disparities in VPTB and PTB between Hmong and white women, as well as between Hmong and other Asian women had become substantial. Moreover, despite gains in post-secondary education among childbearing-age Hmong women, the returns to education for the Hmong are negligible. Higher educational attainment does not confer the same health benefits for Hmong women as it does for whites and other Asian subgroups.

Assessment of critical exposure and outcome windows in time-to-event analysis with application to air pollution and preterm birth study

In reproductive epidemiology, there is a growing interest to examine associations between air pollution exposure during pregnancy and the risk of preterm birth (PTB). One important research objective is to identify critical periods of exposure and estimate the associated effects at different stages of pregnancy. However, population studies have reported inconsistent findings. This may be due to limitations from the standard analytic approach of treating PTB as a binary outcome without considering time-varying exposures together over the course of pregnancy. To address this research gap, we present a Bayesian hierarchical model for conducting a comprehensive examination of gestational air pollution exposure by estimating the joint effects of weekly exposures during different vulnerable periods. Our model also treats PTB as a time-to-event outcome to address the challenge of different exposure lengths among ongoing pregnancies. The proposed model is applied to a dataset of geocoded birth records in the Atlanta metropolitan area between 1999-2005 to examine the risk of PTB associated with gestational exposure to ambient fine particulate matter [Formula: see text]m in aerodynamic diameter (PM[Formula: see text]). We find positive associations between PM[Formula: see text] exposure during early and mid-pregnancy, and evidence that associations are stronger for PTBs occurring around week 30.

Evaluation of gestational age estimate method on the calculation of preterm birth rates

The objectives of this study is to evaluate the impact of vital record gestational age estimation method on resulting preterm birth (PTB) rate calculations. This retrospective analysis reviewed three methods of gestational age estimation using all Ohio live birth records from 2006 to 2009. PTB rates were calculated using each gestational age representation and agreement between classifications of PTB was evaluated with respect to maternal age and race. For each of 608,530 births, gestational age estimates based on last menstrual period (LMP) were compared to clinically-based obstetric estimates. When gestational age estimates did not perfectly agree, differences in the consequential classification of PTB status were evaluated with respect to a third reconciliatory combined gestational age estimate. Mean birth weight at each week of gestation was calculated and compared for all three estimate methods. Substantial agreement was found in PTB classification among gestational age estimates (kappa: 0.748; 95% Confidence Interval: 0.745-0.750); agreement was weakest among black mothers and among mothers less than 20 years of age. LMP-based gestational age estimates did not perfectly agree with obstetric estimates in 238,262 records (39.2%). Disagreement in gestational age led to disagreement in PTB status in 32,033 records (5.3% of total cases) resulting in a 1.8 percentage point difference in PTB rate calculations (11.0% using obstetric and 12.8% using combined estimates). Researchers and policy makers need consistency in selecting which gestational age estimate method to use when calculating or comparing PTB rates.

Small and large size for gestational age and neighborhood deprivation measured within increasing proximity to homes

Neighborhood deprivation is consistently associated with greater risk of low birthweight. However, large birth size is increasingly relevant but overlooked in neighborhood health research, and proximity within which neighborhood deprivation may affect birth outcomes is unknown. We estimated race/ethnic-specific effects of neighborhood deprivation index (NDI) within 1, 3, 5, and 8km buffers around Oregon Pregnancy Risk Assessment Monitoring System (n=3716; 2004-2007) respondents׳ homes on small and large for gestational age (SGA, LGA). NDI was positively associated with LGA and SGA in most race/ethnic groups. The results varied little across the four buffer sizes.

Strips of Hope: Accuracy of Home Pregnancy Tests and New Developments

The first home pregnancy test was introduced in 1976. Since then, pregnancy tests have become the most common diagnostic assay used at home. Pregnancy tests use antibodies to detect human chorionic gonadotropin (hCG). It is an ideal marker of pregnancy since it rises rapidly and consistently in early pregnancy and can be detected in urine. The most advanced home pregnancy test currently available assesses the level of hCG found in urine and claims to provide women with reliable results within just a few weeks of pregnancy. Today, over 15 different types of home pregnancy test are available to buy over the counter in Germany. Many tests claim to be highly accurate and capable of detecting pregnancy before the next monthly period is due, although claims such as 8 days prior to menstruation are unrealistic. However, users and healthcare professionals should be aware that, although all are labelled as CE, there are currently no standard criteria for testing performance and claims. This review provides an overview of the development of home pregnancy tests and the data on their efficacy together with an analysis of published data on the accuracy of hCG for the detection of early pregnancy and studies on the use of home-based pregnancy tests. Preliminary data on some home pregnancy tests available in Germany are presented which indicate that many results do not match the claims made in the package insert. Healthcare professionals and women should be aware that some of the claims made for home pregnancy tests are inconsistent and that common definitions and testing criteria are urgently needed.

Comparison of two measures of gestational age among low income births. The potential impact on health studies, New York, 2005

Recently, the National Association for Public Health Statistics and Information Systems considered changing the definition of gestational age from the current definition based on mother's last normal menstrual period (LMP) to the clinical/obstetric estimate determined by the physician (CE).They determined additional information was needed. This study provides additional insight into the comparability of the LMP and CE measures currently used on vital records among births at risk for poor outcomes. The data consisted of all New York State (NYS) (excluding New York City) singleton births in 2005 among mothers enrolled in the NYS Women Infants and Children (WIC) program during pregnancy. Prenatal WIC records were matched to NYS' Statewide Perinatal Data System. The analysis investigates differences between LMP and CE recorded gestations. Relative risks between risk factors and preterm birth were compared for LMP and CE. Exact agreement between gestation measures exists in 49.6% of births. Overall, 6.4% of records indicate discordance in full term/preterm classifications; CE is full term and LMP preterm in 4.9%, with the converse true for 1.5%. Associations between risk factor and preterm birth differed in magnitude based on gestational age measurement. Infants born to mothers with high risk indicators were more likely to have a CE of preterm and LMP full term. Changing the measure of gestational age to CE universally likely would result in overestimation of the importance of some risk factors for preterm birth. Potential overestimation of clinical outcomes associated with preterm birth may occur and should be studied.

Enrollment in early intervention programs among infants born late preterm, early term, and term

OBJECTIVE

To compare the prevalence of and characteristics associated with early intervention (EI) program enrollment among infants born late preterm (34–36 weeks’ gestation), early term (37–38 weeks’ gestation), and term (39–41 weeks’ gestation).

METHODS

A Massachusetts cohort of 554 974 singleton infants born during 1998 through 2005 and survived the neonatal period was followed until the third birthday of each infant. Data came from the Pregnancy to Early Life Longitudinal Data System that linked birth certificates, birth hospital discharge reports, death certificates, and EI program enrollment records. We calculated prevalence and adjusted risk ratios to compare differences and understand associations.

RESULTS

The prevalence of EI program enrollment increased with each decreasing week of gestation before 41 weeks (late preterm [23.5%],early term [14.9%], and term [11.9%]. In adjusted analyses, the strongest predictors of EI enrollment (adjusted risk ratio ≥1.20) for all gestational age groups were male gender, having a congenital anomaly, and having mothers who were ≥40 years old, non high school graduates, and recipients of public insurance.

CONCLUSIONS

Infants born late preterm and early term have higher prevalence of EI program services enrollment than infants born at term,and may benefit from more frequent monitoring for developmental delays or disabilities.

Racial disparities in pregnancy outcomes in obese women

OBJECTIVE

To estimate the effect of race on perinatal outcomes in obese women.

METHODS

Retrospective cohort study of birth records linked to hospital discharge data for all live born singleton infants ≥37 weeks gestation born to African-American or Caucasian Missouri residents from 2000 to 2006. We excluded major congenital anomalies and women with diabetes or chronic hypertension. Obesity was defined as pre-pregnancy body mass index ≥30 kg/m(2).

RESULTS

There were 312 412 births meeting study criteria. 27.1% (11 776) of African-American mothers and 19.1% (49 415) of Caucasian mothers were obese. There were no differences in cesarean delivery or preeclampsia between obese African-American and obese Caucasian women. Infants of obese African-American women were significantly less likely to be macrosomic (0.9% vs. 2.2%, adjusted odds ratio [aOR] 0.5, 95% confidence interval [CI] 0.4 0.6) and more likely to be low birth weight (3.4% vs. 1.8%, aOR 1.9, 95% CI 1.7, 2.2) compared to infants of obese Caucasian women. Compared to their normal weight peers, obese Caucasian women had a greater relative risk of developing preeclampsia (aOR 3.1, 95% CI 2.9, 3.2) than obese African-American women (aOR 2.1, 95% CI 1.9, 2.4).

CONCLUSION

Racial disparities impact obesity-related maternal and neonatal complications of pregnancy.

Early life factors and risk of childhood rhabdomyosarcoma

Although little is known about etiology of childhood rhabdomyosarcoma (RMS), early life factors are suspected in the etiology. We explored this hypothesis using linked data from the California Cancer Registry and the California birth rolls. Incident cases were 359 children <6-year-old (218 embryonal, 81 alveolar, 60 others) diagnosed in 1988-2008. Controls (205, 173), frequency matched on birth year (1986-2007), were randomly selected from the birth rolls. We examined association of birth characteristics such as birth weight, size for gestational age, and timing of prenatal care with all-type RMS, embryonal, and alveolar subtypes. Crude and adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated using logistic regression. In contrast to a previous study, we observed statistically non-significant association for embryonal subtype among high birth weight (4000-5250 g) children for term births [OR (95% CI): 1.28 (0.85, 1.92)] and all births adjusted for gestational age [OR (95% CI): 1.21 (0.81, 1.81)]. On the other hand, statistically significant 1.7-fold increased risk of alveolar subtype (95% CI: 1.02, 2.87) was observed among children with late or no prenatal care and a 1.3-fold increased risk of all RMS subtypes among children of fathers ≥35 years old at child birth (95% CI: 1.00, 1.75), independent of all covariates. Our finding of positive association on male sex for all RMS types is consistent with previous studies. While we did not find a convincingly positive association between high birth weight and RMS, our findings on prenatal care supports the hypothesis that prenatal environment modifies risk for childhood RMS.

Does advanced maternal age confer a survival advantage to infants born at early gestation?

BACKGROUND

Recent studies have shown that older mothers who deliver at preterm gestation have lower neonatal mortality rates compared with younger mothers who deliver at preterm gestation. We examined the effect of maternal age on gestational age-specific perinatal mortality.

METHODS

We compared fetal, neonatal and perinatal mortality rates among singleton births in the United States, 2003-2005, to mothers aged ≥35 versus 20-29 years. The analysis was stratified by gestational age and perinatal mortality rates were contrasted by maternal age at earlier (22-33 weeks) and later gestation (≥34 weeks). Gestational age-specific perinatal mortality rates were calculated using the traditional perinatal formulation (deaths among births at any gestation divided by total births at that gestation) and also the fetuses-at-risk model (deaths among births at any gestation divided by fetuses-at-risk of death at that gestation).Logistic regression was used to estimate adjusted odds ratios (AOR) for perinatal death.

RESULTS

Under the traditional approach, fetal death rates at 22-33 weeks were non-significantly lower among older mothers (AOR 0.97, 95% confidence interval [CI] 0.91-1.03), while rates were significantly higher among older mothers at ≥34 weeks (AOR 1.66, 95% CI 1.56-1.76). Neonatal death rates were significantly lower among older compared with younger mothers at 22-33 weeks (AOR=0.93, 95% CI 0.88-0.98) but higher at ≥34 weeks (AOR 1.26, 95% CI 1.21-1.31). Under the fetuses-at-risk model, both rates were higher among older vs younger mothers at early gestation (AOR for fetal and neonatal mortality 1.35, 95% CI 1.27-1.43 and 1.31, 95% CI 1.24-1.38, respectively) and late gestation (AOR for fetal and neonatal mortality 1.66, 95% CI 1.56-1.76) and 1.21, 95% CI 1.14-1.29, respectively).

CONCLUSIONS

Although the traditional prognostic perspective on the risk of perinatal death among older versus younger mothers varies by gestational age at birth, the causal fetuses-at-risk model reveals a consistently elevated risk of perinatal death at all gestational ages among older mothers.

Validation of an algorithm to estimate gestational age in electronic health plan databases

PURPOSE

To validate an algorithm that uses delivery date and diagnosis codes to define gestational age at birth in electronic health plan databases.

METHODS

Using data from 225,384 live born deliveries to women aged 15-45 years in 2001-2007 within eight of the 11 health plans participating in the Medication Exposure in Pregnancy Risk Evaluation Program, we compared (1) the algorithm-derived gestational age versus the "gold-standard" gestational age obtained from the infant birth certificate file and (2) the prenatal exposure status of two antidepressants (fluoxetine and sertraline) and two antibiotics (amoxicillin and azithromycin) as determined by the algorithm-derived versus the gold-standard gestational age.

RESULTS

The mean algorithm-derived gestational age at birth was lower than the mean obtained from the birth certificate file among singleton deliveries (267.9 vs 273.5 days) but not among multiple-gestation deliveries (253.9 vs 252.6 days). The algorithm-derived prenatal exposure to the antidepressants had a sensitivity and a positive predictive value of ≥95%, and a specificity and a negative predictive value of almost 100%. Sensitivity and positive predictive value were both ≥90%, and specificity and negative predictive value were both >99% for the antibiotics.

CONCLUSIONS

A gestational age algorithm based upon electronic health plan data correctly classified medication exposure status in most live born deliveries, but trimester-specific misclassification may be higher for drugs typically used for short durations.

Regional variation in late preterm births in North Carolina

Late preterm (LPT) neonates (34 0/7th-36 6/7th weeks' gestation) account for 70% of all premature births in the United States. LPT neonates have a higher morbidity and mortality risk than term neonates. LPT birth rates vary across geographic regions. Unwarranted variation is variation in medical care that cannot be explained by sociodemographic or medical risk factors; it represents differences in health system performance, including provider practice variation. The purpose of this study is to identify regional variation in LPT births in North Carolina that cannot be explained by sociodemographic or medical/obstetric risk factors. We searched the NC State Center for Health Statistics linked birth-death certificate database for all singleton term and LPT neonates born between 1999 and 2006. We used multivariable logistic regression analysis to control for socio-demographic and medical/obstetric risk factors. The main outcome was the percent of LPT birth in each of the six perinatal regions in North Carolina. We identified 884,304 neonates; 66,218 (7.5%) were LPT. After multivariable logistic regression, regions 2 (7.0%) and 6 (6.6%) had the highest adjusted percent of LPT birth. Analysis of a statewide birth cohort demonstrates regional variation in the incidence of LPT births among NC's perinatal regions after adjustment for sociodemographic and medical risk factors. We speculate that provider practice variation might explain some of the remaining difference. This is an area where policy changes and quality improvement efforts can help reduce variation, and potentially decrease LPT births.

Obesity trends and perinatal outcomes in black and white teenagers

OBJECTIVE

Our objective was to explore the trends in prepregnancy body mass index (BMI) for black and white teenagers over time and the association between elevated BMI and outcomes based on race.

STUDY DESIGN

This was a retrospective cohort study of singleton infants (n = 38,158) born to black (34%) and white (66%) teenagers (<18 years of age). We determined the prevalence of elevated prepregnancy BMI between 1993 and 2006 and the association between elevated prepregnancy BMI (primary exposure) and maternal and perinatal outcomes based on race (2000-2006).

RESULTS

The percentage of white teenagers with elevated prepregnancy BMI increased significantly from 17-26%. White and black overweight and obese teenagers were more likely to have pregnancy-related hypertension than normal-weight teenagers; postpartum hemorrhage was increased only in obese black teenagers, and infant complications were increased only in overweight and obese white teenagers.

CONCLUSION

Because the percentage of elevated prepregnancy BMI has increased in white teenagers, specific risks for poor maternal and perinatal outcomes in the overweight and obese teenagers varies by race.

A spatial time-to-event approach for estimating associations between air pollution and preterm birth

The paper describes a Bayesian spatial discrete time survival model to estimate the effect of air pollution on the risk of preterm birth. The standard approach treats prematurity as a binary outcome and cannot effectively examine time varying exposures during pregnancy. Time varying exposures can arise either in short-term lagged exposures due to seasonality in air pollution or long-term cumulative exposures due to changes in length of exposure. Our model addresses this challenge by viewing gestational age as time-to-event data where each pregnancy becomes at risk at a prespecified time (e.g. the 28th week). The pregnancy is then followed until either a birth occurs before the 37th week (preterm), or it reaches the 37th week, and a full-term birth is expected. The model also includes a flexible spatially varying baseline hazard function to control for unmeasured spatial confounders and to borrow information across areal units. The approach proposed is applied to geocoded birth records in Mecklenburg County, North Carolina, for the period 2001-2005.We examine the risk of preterm birth that is associated with total cumulative and 4-week lagged exposure to ambient fine particulate matter.

Sudden infant death syndrome: a re-examination of temporal trends

BACKGROUND

While the reduction in infants' prone sleeping has led to a temporal decline in Sudden Infant Death Syndrome (SIDS), some aspects of this trend remain unexplained. We assessed whether changes in the gestational age distribution of births also contributed to the temporal reduction in SIDS.

METHODS

SIDS patterns among singleton and twin births in the United States were analysed in 1995-96 and 2004-05. The temporal reduction in SIDS was partitioned using the Kitagawa decomposition method into reductions due to changes in the gestational age distribution and reductions due to changes in gestational age-specific SIDS rates. Both the traditional and the fetuses-at-risk models were used.

RESULTS

SIDS rates declined with increasing gestation under the traditional perinatal model. Rates were higher at early gestation among singletons compared with twins, while the reverse was true at later gestation. Under the fetuses-at-risk model, SIDS rates increased with increasing gestation and twins had higher rates of SIDS than singletons at all gestational ages. Between 1995-96 and 2004-05, SIDS declined from 8.3 to 5.6 per 10,000 live births among singletons and from 14.2 to 10.6 per 10,000 live births among twins. Decomposition using the traditional model showed that the SIDS reduction among singletons and twins was entirely due to changes in the gestational age-specific SIDS rate. The fetuses-at-risk model attributed 45% of the SIDS reduction to changes in the gestational age distribution and 55% of the reduction to changes in gestational age-specific SIDS rates among singletons; among twins these proportions were 64% and 36%, respectively.

CONCLUSION

Changes in the gestational age distribution may have contributed to the recent temporal reduction in SIDS.

Influence of definition based versus pragmatic birth registration on international comparisons of perinatal and infant mortality: population based retrospective study

OBJECTIVES

To examine variations in the registration of extremely low birthweight and early gestation births and to assess their effect on perinatal and infant mortality rankings of industrialised countries.

DESIGN

Retrospective population based study.

SETTING

Australia, Canada, European countries, and the United States for 2004; Australia, Canada, and New Zealand for 2007.

POPULATION

National data on live births and on fetal, neonatal, and infant deaths.

MAIN OUTCOME MEASURES

Reported proportions of live births with birth weight/gestational age of less than 500 g, less than 1000 g, less than 24 weeks, and less than 28 weeks; crude rates of fetal, neonatal, and infant mortality; mortality rates calculated after exclusion of births under 500 g, under 1000 g, less than 24 weeks, and less than 28 weeks.

RESULTS

The proportion of live births under 500 g varied widely from less than 1 per 10,000 live births in Belgium and Ireland to 10.8 per 10,000 live births in Canada and 16.9 in the United States. Neonatal deaths under 500 g, as a proportion of all neonatal deaths, also ranged from less than 1% in countries such as Luxembourg and Malta to 29.6% in Canada and 31.1% in the United States. Rankings of countries based on crude fetal, neonatal, and infant mortality rates differed substantially from rankings based on rates calculated after exclusion of births with a birth weight of less than 1000 g or a gestational age of less than 28 weeks.

CONCLUSIONS

International differences in reported rates of extremely low birthweight and very early gestation births probably reflect variations in registration of births and compromise the validity of international rankings of perinatal and infant mortality.

Effect of maternal weight on postterm delivery

OBJECTIVE

Examine the effect of prepregnancy weight and maternal gestational weight gain on postterm delivery rates.

STUDY DESIGN

This was a retrospective cohort study of term, singleton births (N=375 003). We performed multivariable analyses of the association between postterm pregnancy and both prepregnancy body mass index (BMI) and maternal weight gain.

RESULT

Prolonged or postterm delivery (41 or 42 weeks) was increasingly common with increasing prepregnancy weight (P<0.001) and increasing maternal weight gain (P<0.001). Underweight women were 10% less likely to deliver postterm than normal weight women who gain within the recommendations (adjusted odds ratio 0.90 (95% confidence interval 0.83, 0.97)). Overweight women who gain within or above recommendations were also at increased risk of a 41-week delivery. Finally, obese women were at increased risk of a 41-week delivery with increasing risk with increasing weight (below, within and above recommendations adjusted odds ratios 1.19, 1.21, and 1.27, respectively).

CONCLUSION

Elevated prepregnancy weight and maternal weight gain both increase the risk of a postterm delivery. Although most women do not receive preconceptional care, restricting weight gain to the within the recommended range can reduce the risk of postterm pregnancy in normal, overweight and obese women.

Term pregnancy: a period of heterogeneous risk for infant mortality

OBJECTIVE

To estimate the trend of maternal racial and ethnic differences in mortality for early-term (37 0/7 to 38 6/7 weeks of gestation) compared with full-term births (39 0/7 to 41 6/7 weeks of gestation).

METHODS

We analyzed 46,329,018 singleton live births using the National Center for Health Statistics U.S. period-linked birth and infant death data from 1995 to 2006. Infant mortality rates, neonatal mortality rates, and postneonatal mortality rates were calculated according to gestational age, race and ethnicity, and cause of death.

RESULTS

Overall, infant mortality rates have decreased for early-term and full-term births between 1995 and 2006. At 37 weeks of gestation, Hispanics had the greatest decline in infant mortality rates (35.4%; 4.8 per 1,000 to 3.1 per 1,000) followed by 22.4% for whites (4.9 per 1,000 to 3.8 per 1,000); blacks had the smallest decline (6.8%; 5.9 per 1,000 to 5.5 per 1,000) as a result of a stagnant neonatal mortality rate. At 37 weeks compared with 40 weeks of gestation, neonatal mortality rates increase. For Hispanics, the relative risk is 2.6 (95% confidence interval [CI] 2.0-3.3); for whites, the relative risk is 2.6 (95% CI 2.2-3.1); and for blacks, the relative risk is 2.9 (95% CI 2.2-3.8). Neonatal mortality rates are still increased at 38 weeks of gestation. At both early- and full-term gestations, neonatal mortality rates for blacks are 40% higher than for whites and postneonatal mortality rates 80% higher, whereas Hispanics have a reduced postneonatal mortality rate when compared with whites.

CONCLUSION

Early-term births are associated with higher neonatal, postneonatal, and infant mortality rates compared with full-term births with concerning racial and ethnic disparity in rates and trends.

Temporal trends in neonatal outcomes following iatrogenic preterm delivery

Background

Preterm birth rates have increased substantially in the recent years mostly due to obstetric intervention. We studied the effects of increasing iatrogenic preterm birth on temporal trends in perinatal mortality and serious neonatal morbidity in the United States.

Methods

We used data on singleton and twin births in the United States, 1995-2005 (n = 36,399,333), to examine trends in stillbirths, neonatal deaths, and serious neonatal morbidity (5-minute Apgar ≤3, assisted ventilation ≥30 min and neonatal seizures). Preterm birth subtypes were identified using an algorithm that categorized live births <37 weeks into iatrogenic preterm births, births following premature rupture of membranes and spontaneous preterm births. Temporal changes were quantified using odds ratios (OR) and 95% confidence intervals (CI).

Results

Among singletons, preterm birth increased from 7.3 to 8.8 per 100 live births from 1995 to 2005, while iatrogenic preterm birth increased from 2.2 to 3.7 per 100 live births. Stillbirth rates declined from 3.4 to 3.0 per 1,000 total births from 1995-96 to 2004-05, and neonatal mortality rates declined from 2.4 to 2.1 per 1,000 live births. Temporal declines in neonatal mortality/morbidity were most pronounced at 34-36 weeks gestation and larger among iatrogenic preterm births (OR = 0.75, CI 0.73-0.77) than among spontaneous preterm births (OR = 0.82, CI 0.80-0.84); P < 0.001. Similar patterns were observed among twins, with some notable differences.

Conclusion

Increases in iatrogenic preterm birth have been accompanied by declines in perinatal mortality. The temporal decline in neonatal mortality/serious neonatal morbidity has been larger among iatrogenic preterm births as compared with spontaneous preterm births.

Inclusion of non-viable neonates in the birth record and its impact on infant mortality rates in Shelby County, Tennessee, USA

Rates of infant death are one of the most common indicators of a population's overall health status. Infant mortality rates (IMRs) are used to make broad inferences about the quality of health care, effects of health policies and even environmental quality. The purpose of our study was threefold: i) to examine the characteristics of births in the area in relation to gestational age and birthweight; ii) to estimate infant mortality using variable gestational age and/or birthweight criteria for live birth, and iii) to calculate proportional mortality ratios for each cause of death using variable gestational age and/or birthweight criteria for live birth. We conducted a retrospective analysis of all Shelby County resident-linked birth and infant death certificates during the years 1999 to 2004. Descriptive test statistics were used to examine infant mortality rates in relation to specific maternal and infant risk factors. Through careful examination of 1999-2004 resident-linked birth and infant death data sets, we observed a disproportionate number of non-viable live births (≤20 weeks gestation or ≤350 grams) in Shelby County. Issuance of birth certificates to these non-viable neonates is a factor that contributes to an inflated IMR. Our study demonstrates the complexity and the appropriateness of comparing infant mortality rates in smaller geographic units, given the unique characteristics of live births in Shelby County. The disproportionate number of pre-viable infants born in Shelby County greatly obfuscates neonatal mortality and de-emphasizes the importance of post-neonatal mortality.

Delivery indications at late-preterm gestations and infant mortality rates in the United States

OBJECTIVE

The rate of preterm births has been increasing in the United States, especially for births 34 to 36 weeks of gestation (late preterm), which now constitute 71% of all preterm births. The causes for these trends remain unclear. We characterized the delivery indications for late preterm births and their potential impact on neonatal and infant mortality rates.

PATIENTS AND METHODS

Using the 2001 US Birth Cohort Linked birth/death files of 3 483 496 singleton births, we categorized delivery indications as follows: (1) maternal medical conditions; (2) obstetric complications; (3) major congenital anomalies; (4) isolated spontaneous labor: vaginal delivery without induction and without associated medical/obstetric factors; and (5) no recorded indication.

RESULTS

Of the 292 627 late-preterm births, the first 4 categories (those with indications and isolated spontaneous labor) accounted for 76.8%. The remaining 23.2% (67 909) were classified as deliveries with no recorded indication. Factors significantly increasing the chance of no recorded indication were older maternal age; non-Hispanic, white mother; >/=13 years of education; Southern, Midwestern, and Western region; multiparity; or previous infant with a >/=4000-g birth weight. The neonatal and infant mortality rates were significantly higher among deliveries with no recorded indication compared with deliveries secondary to isolated spontaneous labor but lower compared with deliveries with an obstetric indication or congenital anomaly.

CONCLUSIONS

A total of 23% of late preterm births had no recorded indication for delivery noted on birth certificates. Patient factors may be playing a role in these deliveries. It is concerning that these infants had higher mortality rates compared with those born after spontaneous labor at similar gestational ages. Given the excess risk of mortality, patients and providers need to discuss the risks of delivering a preterm infant in the absence of medical indications at 34 to 36 weeks.

An outcome-based approach for the creation of fetal growth standards: do singletons and twins need separate standards?

Contemporary fetal growth standards are created by using theoretical properties (percentiles) of birth weight (for gestational age) distributions. The authors used a clinically relevant, outcome-based methodology to determine if separate fetal growth standards are required for singletons and twins. All singleton and twin livebirths between 36 and 42 weeks’ gestation in the United States (1995–2002) were included, after exclusions for missing information and other factors (n = 17,811,922). A birth weight range was identified, at each gestational age, over which serious neonatal morbidity and neonatal mortality rates were lowest. Among singleton males at 40 weeks, serious neonatal morbidity/mortality rates were lowest between 3,012 g (95% confidence interval (CI): 3,008, 3,018) and 3,978 g (95% CI: 3,976, 3,980). The low end of this optimal birth weight range for females was 37 g (95% CI: 21, 53) less. The low optimal birth weight was 152 g (95% CI: 121, 183) less for twins compared with singletons. No differences were observed in low optimal birth weight by period (1999–2002 vs. 1995–1998), but small differences were observed for maternal education, race, parity, age, and smoking status. Patterns of birth weight-specific serious neonatal morbidity/neonatal mortality support the need for plurality-specific fetal growth standards.

Length of prenatal participation in WIC and risk of delivering a small for gestational age infant: Florida, 1996-2004

OBJECTIVE

To assess the association between length of prenatal participation in WIC and a marker of infant morbidity. By focusing on small for gestational age, we consider one of the possible pathways through which prenatal nutrition affects fetal growth.

DESIGN/METHODS

The study sample consists of 369,535 matched mother-infant pairs drawn from all singleton live births in Florida hospitals from 1996 to 2004. All subjects received WIC and Medicaid-funded prenatal services during pregnancy. We controlled for selection bias on observed variables using a generalized propensity scoring approach and performed separate analyses by gestational age category to control for simultaneity bias.

RESULTS

Ten percent increase in the percent of time in WIC was associated with 2.5% decrease (95% CI: 2.1-3.0%) in the risk of a full-term an SGA infant. The risk was also significantly decreased for very preterm and late preterm infants (29-33 and 34-36 weeks gestation) but not for extremely preterm infants (23-28 weeks gestation).

CONCLUSIONS

The observed small negative dose response relationship between percent of pregnancy spent in WIC and fetal growth restriction implies that longer participation in the program confers a small measure of protection against delivering an SGA infant.

Modeling the pediatric paradox: birth weight by gestational age

The "pediatric paradox" of African versus European American infant mortality is often observed with respect to birth weight, but rarely to gestational age, even though the two measures are biologically related. This paper models the pediatric paradox by birth weight and gestational age simultaneously, using Covariate Density Defined mixture of logistic regressions (CDDmlr) fitted to 1985-1988 New York State births. The model controls for unobserved heterogeneity and isolates the pediatric paradox in the "compromised" subpopulation. The paradox is not limited to low birth weights and/or short gestational ages, but surrounds the normal birth range. Nevertheless, the pediatric paradox is only observed in the marginal distribution of birth weight and not the marginal distribution of gestational age. These results are consistent with the hypothesis that higher fetal losses in the "compromised" subpopulation may be responsible for the pediatric paradox and that African versus European American infant mortality differentials are underestimated.

Infant mortality: explaining black/white disparities in Wisconsin

OBJECTIVES

Understanding the factors contributing to black/white disparities in infant mortality rates in Wisconsin is a prerequisite to decreasing these disparities and improving birth outcomes. We examined multiple determinants of infant mortality to understand the impact of specific risk factors on the infant mortality rates of blacks and whites in Wisconsin.

METHODS

We used the Wisconsin Interactive Statistics on Health database to examine infant mortality data for the 5-year time period, 1998-2002 (N=32,166 black infant births; 272,559 white infant births). We conducted a bivariate analysis of relative risks (RR) of infant mortality (black vs. white) using specific variables available in the database. We then examined the relationship between infant mortality rate and selected risk factors using regression analyses.

RESULTS

Unadjusted, black infants were 3.0 times more likely to die during their first year of life, compared with white infants. Adjusting for gestational age black infants were only 1.9 times more likely to die. The risk was further reduced, after adjusting for birth weight, to 1.3. However, stratifying and adjusting for 8 other multiple variables accounted for some, but not all of the disparity. Black infants who had the same risk profile as white infants still had a 2-fold excess risk of death. In addition, simultaneously controlling for 4 of the 8 risk factors (maternal age, maternal education, adequacy of prenatal care received, and region of the state) also reduced, but did not eliminate, this excess risk (RR was still 2.2 for black infants). Independent of maternal age and region of the state, adequate prenatal care and higher levels of education are significant indicators of the racial disparity between whites and blacks.

CONCLUSIONS

These results suggest that, within a given racial group, increasing access to prenatal care and increasing maternal educational attainment will improve infant mortality rates but will not eliminate the black/white disparity in infant mortality. In fact, these interventions may actually widen the disparity in infant mortality rate between blacks and whites, especially if funds and programs are applied equally throughout the population, rather than targeted to high-risk individuals, who lag significantly behind the majority population. The Wisconsin white population, which has already attained an infant mortality rate of 4.5 per 1,000 live births, will continue to have greatest benefit from these programs compared to blacks who have a rate of 19.2 in 2004; thus, the disparity is not eliminated and the gap widens probably due to differential uptake of health messages secondary to health literacy issues. Further research is needed to fully understand the additional, more difficult to measure factors that contribute significantly to infant mortality, especially among black women.