Extrauterine neuromaturation of low risk preterm infants.

The objective of the study was to follow neuromaturation in preterm infants. From serial exams in 90 low risk very low birthweight infants, each infant's Maturity Scores (the sum of tone, reflex, and response items) were plotted against postmenstrual age (PMA) when examined. Each infant's estimated line of best fit provides two descriptors of that infant's neuromaturation: slope (Individual Maturity Slope) and y-value (Predicted Maturity Score at 32-wk PMA). We found that Maturity Scores increased with PMA; 96% had correlation coefficients >0.8. Mean Actual and Predicted Maturity Scores at 32-wk PMA were 60 and 58, respectively, in 65 infants. When stratified by gestational age, Mean Actual Maturity Score at 30-wk PMA were 50 whether infants were 1 or several weeks old when examined. Therefore, low risk preterm infants demonstrated individual variability in rate of neuromaturation. Tone, reflexes, and responses nonetheless emerged in a predictable pattern, whether neuromaturation was intrauterine or extrauterine. This unique tool that measures preterm neuromaturation requires expertise but no technology. It has an exciting potential for providing insight into how emerging central nervous system function and structure influence each other, as well as how the central nervous system recovers from injury.

The influence of maternal mobility on birth outcomes of non-hispanic blacks.

BACKGROUND: We investigated whether the "healthy migrant" effect is applicable to an internally mobile U.S.-born population, that is, whether infants born to women that moved within the United States had better birth outcomes compared to those infants whose mothers did not move. METHODS: This study used 1995-2001 National Center for Health Statistics live birth/infant death cohort files of singleton infants born in the U.S. to non-Hispanic Black women. RESULTS: Infants born to women who moved had significantly lower risks of low birth weight, preterm birth, and SGA compared to the non-mobile group. CONCLUSIONS: There is evidence to support the healthy migrant effect in an internally migrant Black population. The findings of this study suggest infants of non-Hispanic Black mothers who were born in one state and moved prior to delivery had more positive birth outcomes when compared to those infants of women who did not move prior to delivery.

Racial disparities in perinatal outcomes and pregnancy spacing among women delaying initiation of childbearing.

INTRODUCTION: Reducing racial/ethnic disparities is a key objective of the Healthy People 2010 initiative. Unfortunately, racial disparities among women delaying initiation of childbearing have received limited attention. As more women in the US are delaying initiation of childbearing, it is important to examine racial disparities in reproductive health outcomes for this subgroup of women. OBJECTIVE: To examine racial disparities in perinatal outcomes, interpregnancy interval, and to assess the risk for adverse outcomes in subsequent pregnancy for women delaying initiation of childbearing until age 30 or older compared to those initiating childbearing at age 20-29. METHODS: We conducted a retrospective cohort study using the Missouri maternally linked cohort files 1978-1997. Final study sample included 239,930 singleton sibling pairs (Whites and African Americans). Outcome variables included first and second pregnancy outcomes (fetal death, low birth weight, preterm delivery and small-for-gestational age) and interpregnancy interval between first and second pregnancy. Independent variables included maternal age at first pregnancy and race. Analysis strategies used involved stratified analyses and multivariable unconditional logistic regression; interactions between maternal race, age and interpregnancy interval were examined in the regression models. RESULTS: Compared to Whites, African American mothers initiating childbearing at age 30 or older had significantly higher rates of adverse outcomes in the first and second pregnancy (P < 0.0001). Generally, African Americans had significantly higher rates of second pregnancy following intervals <6 months compared to Whites; however, no significant racial differences were noted in interpregnancy interval distribution pattern after controlling for maternal age at first pregnancy. African Americans delaying initiation of childbearing had significantly higher risk for adverse perinatal outcomes in the second pregnancy compared to Whites after controlling for potential confounders, however there were no significant interactions between maternal age at first pregnancy, race and short interpregnancy interval. CONCLUSION: Although African Americans were less likely to delay initiation of childbearing than were White women, their risk for adverse perinatal outcomes was much greater. As health care providers strive to address racial disparities in birth outcomes, there is need to pay attention to this unique group of women as their population continues to increase.

Pregnancy spacing among women delaying initiation of childbearing.

INTRODUCTION: An increasing proportion of women in the US and other countries delay initiation of childbearing until their thirties. Little is known about their subsequent pregnancies, particularly with regard to pregnancy spacing. OBJECTIVES: To determine interpregnancy interval (IPI) patterns, factors associated with IPI among women delaying initiation of childbearing until their thirties, and ascertain if delay in initiation of childbearing is associated with increased likelihood for short interpregnancy interval of less than 6 months. METHODS: A retrospective cohort study was performed using the Missouri maternal linked file for 1978-1997, inclusive. Analysis was limited to mothers aged 20-50 years at first pregnancy, having a first and second pregnancy during the study period; the sample size included 242,559 mother-infant pairs. Analysis strategies included stratified analysis, and multivariable logistic regression. Interpregnancy interval was main outcome variable, and was grouped in seven categories: 0-5, 6-11, 12-17, 18-23, 24-59, 60-119, >or=120 months. RESULTS: The mean interpregnancy interval was significantly shorter for women delaying start of childbearing (>or=30 years) compared to 20-29 year olds. Observed intervals are 31 (+/-24) months for mothers aged 20-29 years, 25 (+/-17) months for mothers aged 30-34 years, 21 (+/- 14) for 35-39 year olds, and 19 (+/-16) for 40-50 year olds (P < 0.0001). A significant trend for shorter intervals was noted as maternal age at first pregnancy increased (P < 0.0001). Factors associated with interpregnancy interval for women delaying initiation of childbearing included adverse outcome in preceding pregnancy, and low educational status. Mothers aged 35 and above at first pregnancy had increased odds for a second pregnancy following short IPI <6 months; (35-39 years OR = 1.26 95% CI 1.11-1.44; 40-50 OR = 1.91 95% CI 1.13-3.24). Mothers aged 30-34 years have lower odds for short IPI (OR = 0.93 95% CI 0.87-0.99). CONCLUSION: First time mothers aged 35 and above have higher odds of having a second pregnancy shortly after their first pregnancy. Given the increasing number of first time mothers aged 35 and above, these findings are of relevance for preconception counseling for this unique population of women.

Interpregnancy interval and subsequent perinatal outcomes among women delaying initiation of childbearing.

AIM: While delayed initiation of childbearing is associated with adverse perinatal outcomes, whether or not risk persists and whether interpregnancy interval (IPI) affects the subsequent pregnancy remains unclear. OBJECTIVES: To examine second-pregnancy perinatal outcomes for women initiating childbearing age > or = 30 compared to those initiating childbearing aged 20-29, specifically examining the distribution of adverse perinatal outcomes, and their associations with the interpregnancy interval. METHODS: Retrospective cohort study using the Missouri maternally linked files 1978-1997. Perinatal outcomes included fetal death, low birthweight, preterm birth and small-for-gestational age. Predictor variables included maternal age at first pregnancy and IPI between the first and second pregnancy. RESULTS: With an increasing maternal age at first pregnancy, rates of very low birthweight (P = 0.0095), preterm delivery (P = 0.0126), moderately preterm (P = 0.0458), and extremely preterm (P = 0.0008) in the second pregnancy increased, while the rate of small-for-gestational age (P < 0.0001) declined. Interpregnancy intervals <6 and > or = 60 months were associated with a higher rate of adverse outcomes after controlling for maternal age at first pregnancy. Intervals of 12-17 months had the lowest rate of adverse outcomes for mothers 35+. Maternal age > or = 35 years at first pregnancy and IPI <6 months were independent risk factors for an adverse outcome in the second pregnancy, however no statistical interaction between these factors was observed. CONCLUSION: Delayed initiation of childbearing is associated with a persistent risk of adverse perinatal outcomes in the second pregnancy, with a short IPI contributing to this risk. As numbers of women delaying childbearing beyond age 30 increase, providers should consider these risks in counseling women about their reproductive plans.

Obesity and extreme obesity: new insights into the black-white disparity in neonatal mortality.

OBJECTIVE: To estimate whether the preponderance of obesity among black women could explain the black-white disparity in neonatal mortality. METHODS: This is a population-based study using longitudinally collected data among pregnant women from the state of Missouri spanning almost two decades (1978-1997). Obesity is defined in this study as body mass index (BMI) of at least 30 and further categorized into the typically reported three subclasses: class I (BMI 30.0-34.9), class II (BMI 35.0-39.9), and extreme/morbid obesity (BMI at least 40). The main outcome measures were neonatal mortality, early neonatal mortality, and late neonatal mortality. RESULTS: Overall, neonatal mortality and early neonatal mortality but not late neonatal mortality increased with higher obesity subclass, with the greatest risk registered among morbidly obese mothers (hazards ratio for neonatal mortality 1.3; 95% confidence interval [CI] 1.1-1.5; hazards ratio for early neonatal mortality 1.3; 95% CI 1.1-1.5). Among blacks, the risk for neonatal, early, and late neonatal mortality increased significantly with rising BMI (50-100% increments). However, offspring of obese white mothers had no elevated risks for any of the three indices of mortality regardless of maternal obesity subclass. CONCLUSION: Neonates of obese black mothers have an elevated risk of mortality throughout the neonatal period, whereas those of obese white mothers do not. Obesity among black mothers may contribute to the persistent black-white disparity in infant survival in the United States and could provide an avenue for narrowing the black-white gap in infant mortality. LEVEL OF EVIDENCE: II.

Pregnancy outcomes of American Indians: contrasts among regions and with other ethnic groups.

OBJECTIVES: The two-fold purpose of this analysis is first to contrast the maternal risk factors and birth outcomes of American Indians (AIs) with other race/ethnic groups and to compare the maternal risk factors and birth outcomes of AIs by region to assess whether there are geographic variations in the adverse outcomes that might suggest intervention strategies. STUDY DESIGN: This study used the National Center for Health Statistics live birth infant death cohort files from 1995-2001. Singleton live births to U.S. resident mothers were selected. The analyses were limited to non-Hispanic American Indians, including Aleuts and Eskimos (n = 239,494), Non-Hispanic White (n = 15,488,133), and Hispanic births (n = 5,284,978). RESULTS: This comparison of birth characteristics and outcomes by ethnic group revealed that AIs have more adverse maternal risk factors (e.g., unmarried and <18 years of age) than Whites and Hispanics. After adjustment for these factors, AIs have higher risks of low birth weight and preterm birth and elevated risks of postneonatal and infant mortality. Their cause-specific rates for perinatal, SIDS, injury and infection are also higher. The regional analysis indicated the South/Northeast have more low birth weight and preterm problems, but the Mid-West has the highest risks of infant mortality among LBW infants gestational age-specific mortality rates, and mortality from SIDS. CONCLUSIONS: These data show that AIs are not a homogenous group as evinced by distinct regional differences. SIDS is mainly a problem in the Mid-West, suggesting the involvement of environmental factors in that region. Further investigation is needed to examine the current AI perinatal health concerns.

The increasing racial disparity in infant mortality rates: composition and contributors to recent US trends.

OBJECTIVES: We examined trends in birthweight-gestational age distributions and related infant mortality for African American and white women and calculated the estimated excess annual number of African American infant deaths. STUDY DESIGN: Live births to US-resident mothers with a maternal race of white or African American were selected from the National Center for Health Statistics' linked live birth-infant death cohort files (1985-1988 and 1995-2000). RESULTS: The racial disparity in infant mortality widened despite an increasing rate of white low-birthweight infants. White preterm infants had relatively greater gains in survival and the white advantage in survival at term increased. Annually, African American women experience approximately 3300 more infant deaths than would be expected. CONCLUSION: The increasing US racial disparity in infant mortality is largely influenced by changes in birthweight-gestational age-specific mortality, rather than the birthweight-gestational age distribution. Improvement in the survival of white preterm and low-birthweight infants, probably reflecting advances in and changing access to medical technology, contributed appreciably to this trend.

Extreme obesity and risk of stillbirth among black and white gravidas.

OBJECTIVE: To estimate the risk for stillbirth among three generally accepted obesity subtypes based on severity. METHODS: We used the Missouri maternally linked cohort data containing births from 1978 to 1997. Using prepregnancy weight and height, mothers were classified on the basis of calculated body mass index (BMI) above 30 into three subsets: class I (30-34.9), class II (35-39.9), and extreme obesity (greater than or equal to 40). Using normal-weight, white women (18.5-24.9) as a reference, we applied Cox proportional hazard regression models to estimate risks for stillbirth. RESULTS: The prevalence of obesity in pregnant women was 9.5% (12.8% among blacks and 8.9% among whites). Overall, obese mothers were about 40% more likely to experience stillbirth compared with nonobese gravidas (adjusted hazard ratio 1.4; 95% confidence interval [CI] 1.3-1.5). The risk for stillbirth increased in a dose-dependent fashion with increase in BMI: class I (adjusted hazard ratio 1.3; 95% CI 1.2-1.4); class II (adjusted hazard ratio 1.4; 95% CI 1.3-1.6) and extreme obesity (adjusted hazard ratio 1.9; 95% CI 1.6-2.1; P for trend <.01). Obese black mothers experienced more stillbirths than their white counterparts (adjusted hazard ratio 1.9; 95% CI 1.7-2.1 compared with adjusted hazard ratio 1.4; 95% CI 1.3-1.5). The black disadvantage in stillbirth widened with increase in BMI, with the greatest difference observed among extremely obese black mothers (adjusted hazard ratio 2.3; 95% CI 1.8-2.9). CONCLUSION: Obesity is a risk factor for stillbirth, particularly among extremely obese, black mothers. Strategies to reduce black-white disparities in birth outcomes should consider targeting obese, black women. LEVEL OF EVIDENCE: II.

Comparison of gestational age classifications: date of last menstrual period vs. clinical estimate.

PURPOSE: The purpose was to compare the two different measures of gestational age currently used on birth certificates (the duration of pregnancy based on the date of last menstrual period [LMP] and the clinical estimate [CE] as related to health status indicators. We contrasted these measures by race/ethnicity. METHODS: NCHS natality files for 2000-2002 were used, selecting cases of single live birth to U.S. resident mothers with both LMP and CE gestational age information. RESULTS: Approximately 75% of the records had valid LMP and CE values and for approximately one-half of these, the LMP and CE values did not exactly agree. Overall and for each race and ethnic group, the LMP measures resulted in higher proportions of very preterm, preterm, postterm and SGA births. CE value provided preterm rates of 7.9% and for LMP, 9.9%. The odds ratio of preterm birth for African-Americans using the CE measure was 1.78 [95% Cl 1.77-1.79]. The odds ratio using LMP was 1.93 [95% Cl 1.92-1.94]. Whites were the referent population. CONCLUSIONS: Different measures of gestational age result in different overall and race-specific rates of very preterm, preterm, postterm, and SGA births. These findings indicate that substituting or combining these measures may have consequences.

Mode of delivery and the survival of macrosomic infants in the United States, 1995-1999.

BACKGROUND: Although increases in perinatal mortality risk associated with fetal macrosomia are well documented, the optimal route of delivery for fetuses with suspected macrosomia remains controversial. The objective of this investigation was to assess the risk of neonatal death among macrosomic infants delivered vaginally compared with those delivered by cesarean section. METHODS: Data were derived from the U.S. 1995-1999 Linked Live Birth-Infant Death Cohort files and term (37-44 wk), single live births to United States resident mothers selected. A proportional hazards model was used to analyze the risk of neonatal death associated with cesarean delivery among 3 categories of macrosomic infants (infants weighing 4,000-4,499 g; 4,500-4,999 g; and 5,000+ g). RESULTS: After controlling for maternal characteristics and complications, the adjusted hazard ratio for neonatal death associated with cesarean delivery among the 3 categories of macrosomic infants was 1.40, 1.30, and 0.85. CONCLUSIONS: Although cesarean delivery may reduce the risk of death for the heaviest infants (5,000+ g), the relative benefit of this intervention for macrosomic infants weighing 4,000-4,999 g remains debatable. Thus, policies in support of prophylactic cesarean delivery for suspected fetal macrosomia may need to be reevaluated.

Delivering a very low birth weight infant and the subsequent risk of divorce or separation.

BACKGROUND: The simultaneous rise over the last two decades in the U.S. in the proportion of VLBW (<1500 grams) deliveries and the improvement in their chance of survival has increased the number of families caring for VLBW infants and children. The families of VLBW infants with adverse outcomes can face psychological and monetary stresses, which in turn may influence marital instability and increase the risk of divorce or separation. The purpose of this paper is to identify the relationship of having a VLBW birth with the probability of divorce or separation in the first two years following delivery. METHODS: We use data from the 1988 National Maternal and Infant Health Survey (NMIHS). This national stratified, systematic "follow-back" survey augments information from birth records in 1988 by obtaining information on social, demographic, and economic variables from women that delivered a baby in 1988. We estimate a proportional discrete time hazard model of transitions to divorce/separation. RESULTS: Parents of a VLBW infant have 2-fold higher odds of divorce/separation compared with parents of a child with a birth weight greater than 1500 grams. Two years after delivery of a non-VLBW baby 95 percent of the marriages remain stable, while about 90 percent of the marriages remain stable following the birth of a VLBW baby. If the pregnancy was not desired, then only 85 percent of the marriages remain stable 2 years following the delivery of a VLBW infant. CONCLUSIONS: There is an evident need to counsel and support families with VLBW infants on mechanisms to cope with the initial stressors that can be anticipated to arise.

First-time births among women 30 years and older in the United States: patterns and risk of adverse outcomes.

OBJECTIVE: To update the trends in initiation of childbirth by age of the mother, describing the characteristics of women having their first child at age 30 or above, and to determine the risk for adverse pregnancy outcomes for this group of women. STUDY DESIGN: This was a cross-sectional study using National Center for Health Statistics linked live birth and infant death cohort files from 1995 to 2000, and Natality file from 1980 to 2002. Analysis was limited to index pregnancies only. Logistic regression analysis was used to determine the risk of poor outcomes. RESULTS: There is a decreasing trend of first-time births to women 20-29 years old, while births to women 30 and older are showing a continued rise. As compared to 20-29-year-olds, women who start childbearing at age 30 or older are at increased risk of maternal complications in general. However, 30-34-year-olds have a reduced risk for pregnancy-induced hypertension and pre-existing hypertension. Infants born to women aged 30 and above are at increased risk for prematurity and low birth weight in addition to fetal and infant mortality. CONCLUSION: Because of the increasing trend of women starting childbearing in their 30s and the increased risk for poor outcomes in older women, health providers need to pay extra attention to this group of women as they plan and deliver services for them.

Fetal growth risk curves: defining levels of fetal growth restriction by neonatal death risk.

OBJECTIVE: We developed a fetal growth risk curve that delineates the birth weight values for gestational age that reflect a 2-, 2.5-, and 3-fold neonatal death risk relative to infants with normal fetal growth. STUDY DESIGN: We analyzed 18,085,052 single gestation infants (25-42 weeks) who were born to US resident mothers from 1996 to 2000. Multivariate models were used to predict the relationship between neonatal death and birth weight percentile. Fetal risk curves were derived on the basis of birth weight percentile-specific neonatal mortality rates that were relative to an average rate of neonatal death for a comparison group that was representative of typical growth (ie, infants between 45th-55th birth weight percentiles for gestational age). RESULTS: The 10th percentile of birth weight for gestational age is associated with an increased but variable risk of neonatal death relative to the comparison group across the spectrum of gestational ages. At 26 weeks of gestation, infants at the 10th percentile experienced a 3-fold risk of dying within the first 28 days of life (relative to the comparison group); whereas at 40 weeks, the risk was 1.13. CONCLUSION: Fetal growth risk curves facilitate the identification of populations of infants whose risk of death are deemed excessive compared with that of infants at the norm of fetal growth and may be useful for counseling pregnant women.

Childhood pregnancy (10-14 years old) and risk of stillbirth in singletons and twins.

OBJECTIVE: To clarify the association between childhood pregnancy and risk of stillbirth. STUDY DESIGN: We analyzed singleton and twin pregnancies that occurred in children (10-14 years old) in the United States from 1989 to 2000. We estimated the absolute and relative risks of stillbirth by using 15- to19-year-old and 20- to 24-year-old mothers as comparison groups. RESULTS: The analysis involved 17.8 million singletons and 337,904 individual twins. The rate of stillbirth was highest in pediatric mothers for both singletons (12.8/1000) and twins (56/1000) compared with adolescent (6.8/1000 in singletons and 29/1000 in twins) and mature (5.5/1000 in singletons and 20/1000 in twins) mothers. After adjusting for confounding characteristics, pediatric mothers continued to exhibit significantly elevated risk for stillbirth in both singletons (odds ratio, 1.57; 95%CI, 1.49-1.66) and twins (odds ratio, 1.97; 95%CI, 1.42-2.73). Preterm birth rather than small size for gestational age was revealed by means of sequential modeling to account for the excess risk of stillbirth observed in pediatric gravidas. CONCLUSION: Pregnancy in childhood is a risk factor for stillbirth; shortened gestation rather than reduction in fetal growth is the mediating pathway.

The association between small-for-gestational age triplet pregnancies and neonatal mortality: a novel approach to growth assessment in multiple gestations.

It is customary to estimate the uteroplacental function in singletons by defining appropriateness of birth weight by gestational age. Such a measure, however, is not available for the entire multiple pregnancy set. We evaluate a new index, total triplet birth weight, expressed as multiples of the median (MOM) birth weight of singleton gestations. We categorized triplet sets as small-, appropriate-, and large-for-gestational age pregnancies (SGA, AGA, and LGA, respectively), defined as <1 SD, +/-1 SD, and >1 SD from the mean MOM birth weight of singleton gestations. We used the 1995-1998 US matched multiple dataset to evaluate this index and to explore the association between the three categories in terms of risk of neonatal mortality. The mean +/- SD MOM value was 2.3 +/- 0.4. There was an inverse correlation between mean MOM and gestational age. LGA pregnancy status was associated with multiparity, race (being white), and high social status (education). Maternal age did not influence MOM scores. Compared with the LGA pregnancy category, the risk for neonatal mortality was more than doubled in the AGA pregnancy group and more than 9-fold in the SGA pregnancy category. We propose that this new measure could be a useful proxy for the uteroplacental efficiency in a similar way that the SGA designation works for singleton infants.

Preterm delivery and age of SIDS death.

PURPOSE: The aim of the study is to (i) reexamine risk factors for sudden infant death syndrome (SIDS) and (ii) describe the relationship between length of gestation and age at death from SIDS. METHODS: To evaluate risk factors for SIDS, we used multivariable logistic regression and included maternal demographic characteristics, maternal health and behavioral factors, and infant characteristics, including fetal growth, using US national linked birth and death files from 1996 to 1998. We used multivariable linear regression with mean postnatal age of death as the outcome of interest, controlling for the factors listed (referent length of gestation, 40 to 41 weeks). RESULTS: The crude SIDS rate was 0.7 deaths/1000 live births (8199 deaths). Length of gestation was a strong risk factor for SIDS, with the adjusted odds ratio (OR) greatest at shorter gestations: 28 to 32 weeks (OR, 2.9; 95% confidence interval, 2.6-3.2). Infants with gestations of 22 to 27 and 28 to 32 weeks died at mean ages of 20.9 (SD = 0.8) and 15.3 (SD = 0.5) weeks, respectively (p < or = 0.002). Term infants (40 to 41 weeks) died of SIDS at an adjusted mean age of 14.5 (SD = 0.4) weeks. CONCLUSIONS: Preterm birth continues to be a strong risk factor for SIDS after controlling for fetal growth. With increasing gestational age, mean age of SIDS death decreases considerably, with the postnatal age of death of very preterm infants 6 weeks later than that of term infants.

The healthy migrant theory: variations in pregnancy outcomes among US-born migrants.

Various studies have observed that infants born to foreign-born women have better birth outcomes (lower rates of preterm, low birth weight, and infant mortality) than those delivered to US-born women. While much attention has been given to the "healthy migrant effect" as an explanation for these positive outcomes, this theory has not been examined in an internally migrant population. The purpose of this study is to examine the relationship between maternal mobility history and birth outcomes among infants born to US resident mothers of Mexican origin. The study used 1995-1999 National Center for Health Statistics (NCHS) live birth/infant death cohort files of singleton infants delivered in the US to white women of Mexican origin (n = 2,446,253). Maternal mobility history (MMH), which refers to the relationship between the maternal place of birth and the state of residence at delivery, was categorized into the four following groups: (a) foreign-born-place of birth outside the US and delivery in the US; (b) outside-region-place of birth in one US region and delivery in another US region; (c) within-region-place of birth in one US region and delivery in a different state in the same US region; and (d) within-state-place of birth and delivery in the same US state. Consistently, there is evidence to support the healthy migrant effect in an internally migrant population. Unique to this study are the findings that infants born to mothers with outside-region MMH had a lower risk of low birth weight (LBW) and small-for-gestational age (SGA) compared to those who did not move. Overall, this study provides evidence that the healthy migrant effect and its relationship to birth outcomes can be applied to an internally migrant population.

Racial and ethnic differences in perinatal mortality: the role of fetal death.

PURPOSE: We investigate whether variations in infant mortality rates among racial/ethnic groups could be explained by variations in fetal mortality rates where relatively higher infant mortality rates may correspond to lower fetal mortality rates due to possible systematic differences in reporting of fetal death compared to live births. METHODS: Using US perinatal data from 1995 to 1999, we calculated crude mortality rates, birth weight-specific fetal and hebdomadal mortality rates, risks of perinatal death, and the risk of being classified as a fetal death versus other period death among infants born to Non-Hispanic White, Non-Hispanic Black, and Hispanic mothers. RESULTS: Two-fold disparities between Whites and Blacks persist for all mortality categories. Black low birth-weight deliveries, compared to Whites, have perinatal advantages in both fetal and hebdomadal periods. Hispanics were less likely than Whites to be reported as a fetal versus a hebdomadal death. CONCLUSIONS: While these data suggest some underreporting of Black fetal deaths, they provide little evidence that Black-White disparities in infant mortality are a function of variations in classifying a death occurring at delivery as either a fetal death or as a live birth-infant death. These data suggest that the lack of a White-Hispanic disparity in fetal mortality rates may be influenced by underreporting.

State-specific trends in preterm delivery: are rates really declining among non-Hispanic African Americans across the United States?

OBJECTIVES: This study sought to examine state-specific trends in preterm delivery rates among non-Hispanic African Americans and to assess whether these rates are influenced by misclassification of gestational age. METHODS: The sample population consisted of singleton non-Hispanic White and non-Hispanic African-American infants born in 1991 and 2001 to U.S. resident mothers. For both time periods, state-specific and national preterm delivery rates were calculated for all infants, stratified by infant race/ethnicity. Next, birth-weight distributions within strata of gestational age were studied to explore possible misclassifications of gestational age. Lastly, state-specific and national preterm delivery rates among infants who weighed less than 2,500 g were separately computed. RESULTS: National analyses showed that the frequency of preterm delivery increased by 15.8% among non-Hispanic Whites but declined by 10.3% among non-Hispanic African Americans over the same period. For both subgroups, a bimodal distribution of birth weights was apparent among preterm births at 28-31 weeks of gestation. The second peak with its cluster of normal-weight infants was more prominent among non-Hispanic African Americans in 1991 than in 2001. After excluding preterm infants who weighed 2,500 g or more, the national trends persisted. State-specific analyses showed that preterm delivery rates increased for both subgroups in 13 states during this period. Of these 13, 6 states had a number of non-Hispanic African-American births classified as preterm that were apparently term births mistakenly assigned short gestational ages. Such misclassification was more frequent in 1991 than in 2001 and inflated 1991 rates. CONCLUSION: There is heterogeneity in state-specific preterm delivery rates. Such differences are often overlooked when aggregate results are presented.