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Biomedical subjects

Greg R Alexander

Publications and source records attributed to Greg R Alexander.

At least 19 recordsLinked to original sources
PubMed2006

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.

Birth Weight↗
PubMed2006

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.

Adolescent↗
PubMed2006

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.

Adolescent↗
PubMed2006

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.

Adolescent↗
PubMed2006

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.

Adolescent↗
PubMed2006

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.

Cesarean Section↗
PubMed2006

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.

Adult↗
PubMed2006

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.

Adult↗
PubMed2005

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.

Adult↗
PubMed2005

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.

Black People↗
PubMed2005

Survival of "pre-viable" infants in the United States.

OBJECTIVE: We investigated temporal trend in survival of pre-viable (200-499 g) fetuses over the previous decade, and estimated future survival rates based on previous and current survival thresholds. DESIGN, SETTING AND PARTICIPANTS: This was a retrospective cohort study on live-born pre-viable fetuses (200-499 g) in the United States comparing two period cohorts; 1985-1988 versus 1995-1999. We computed survival of pre-viable babies (who were still alive at 24 hours) during the two periods and based on these results, we estimated future survival rates for the coming decades. MAIN OUTCOMES: Survival beyond the neonatal period. RESULTS: About 35 million live births were analyzed for the two periods. In the first period (1985-1988), 927 live births among pre-viable fetuses were recorded while in the second period (1995-1999) 2585 were counted, equivalent to a birth rate of 60.6 and 131.9 per million live births respectively. This corresponds to an increase of more than 100% across the decade (p for trend < 0.0001). Survival improved by about 50% across the period, from 12.0% to 17.4% (p < 0.0001). Based on these results, the survival rate among pre-viable fetuses will be expected to rise to about 24.0% within the next 6 years (2010). CONCLUSIONS: Survival among pre-viable fetuses is increasing in the United States. This raises ethical, legal and medical issues concerning the defined viability status of these babies, which is currently described as "non-viable".

Birth Certificates↗
PubMed2005

A guide to reviewing manuscripts.

MCH professionals play an invaluable role by serving as peer-reviewers for their professional journal. The peer-review process is a fundamental part of maintaining the scientific rigor and professional relevance of our field's literature. The purpose of this article is to provide guidance for the review of manuscripts submitted for publication to professional and scientific journals. In addition, a structure is proposed for undertaking a review and organizing the written response to the editor and the authors.

Guidelines as Topic↗
PubMed2005

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

OBJECTIVES: Prenatal care is an established mechanism for identifying and managing risk factors impacting pregnancy outcomes. Despite aggressive efforts in the United States (US) to assure that all women begin care in the first trimester, every year about 70,000 women in the US receive no care prior to delivery. We hypothesized that US women receiving no prenatal care comprise clusters (subgroups) with distinctive behavioral, socio-demographic, and medical risks and that birth outcomes differ among the clusters. METHODS: White, Black, and Hispanic women (n = 126,220) receiving no prenatal care and delivering a live, singleton infant were identified from linked birth and death certificates for years 1995 through 1997. Cluster analysis was used to group women with similar characteristics, and cluster assignment was evaluated using discriminant analysis. Birth outcomes for any care and no-care women were then examined using logistic regression. RESULTS: Six replicable clusters of women with no care were identified. Birth outcomes varied significantly among clusters and were two to four times worse for no-care clusters compared to outcomes for women receiving any care. CONCLUSIONS: Cluster analysis is an effective alternative for grouping individuals for use in public health education, intervention, and outreach programming. Women receiving no prenatal care were characteristically different from women receiving any care in this study, but they did not represent a homogenous group. Findings suggest that interventions should target reducing the proportion of women receiving no care and should be tailored to specific no-care clusters.

Adolescent↗
PubMed2005

Perinatal mortality associated with abruptio placenta in singletons and multiples.

OBJECTIVE: This study was undertaken to investigate the association among plurality (number of fetuses per pregnancy), abruptio placenta, and perinatal mortality. STUDY DESIGN: A retrospective cohort study on 15,051,872 singletons, 413,619 twins, and 22,585 triplets delivered in the United States between 1995 and 1998 was conducted. We compared the occurrence of perinatal death between pregnancies complicated by abruptio placenta and those without with the use of adjusted odds ratios. The generalized estimating equations framework was applied to adjust for intracluster correlations among multiples. RESULTS: Placental abruption occurred among 93,968 singletons (6.2 per 1000), 5051 twin (12.2 per 1000), and 353 triplet (15.6 per 1000) gestations ( P for trend<.0001). Placental abruption was associated with significant risk of mortality irrespective of the plurality subtype. Perinatal mortality was greatest among singletons (adjusted odds ratio [95% CI]=14.3[13.2-15.4]), followed by twins (4.4[3.9-4.9]) and least among triplets (3.0[2.0-4.6]) ( P for trend<.0001). CONCLUSION: As plurality increases from 1 to 3, the risk of placental abruption rises, whereas the risk of abruptio-associated perinatal mortality declines.

Abruptio Placentae↗
PubMed2005

Fetal and neonatal mortality risks of multiple births.

The purpose of this article is to describe the perinatal mortality experience and mortality-related risk factors of recent US multiple births. First, we describe trends in fetal and neonatal mortality rates for singleton and multiple births to understand if the improvements in perinatal mortality in the United States are equally or differentially reflected among multiple births. Because the characteristics of women who have multiple deliveries differ from those of mothers of singletons, we describe the risk of fetal and neonatal mortality by maternal characteristics and plurality. Finally, we examine the distribution and fetal and neonatal mortality risk of singleton and multiple births by birth weight and gestational age to provide an updated assessment and contrast of their comparative survival chances within similar birth weight-gestational age categories of intrauterine development.

Adult↗
PubMed2005

Secular trends in cesarean delivery rates among macrosomic deliveries in the United States, 1989 to 2002.

OBJECTIVES: We describe national trends in cesarean delivery rates among macrosomic infants during 1989 to 2000 and evaluate the maternal characteristics and risk factors for macrosomic infants delivered by cesarean section as compared to macrosomic infants delivered vaginally. STUDY DESIGN: We analyzed US 1989 to 2000 Natality files, selecting term (37 to 44 week) single live births to U.S. resident mothers. We compare macrosomic infants (4000 to 4499, 4500 to 4999 and 5000+ g infants) to a normosomic (3000 to 3999 g) control group. RESULTS: The proportion of cesarean deliveries among 5000+ g infants increased significantly over the time period. The adjusted odds ratio of cesarean delivery increased for all macrosomic categories over the 12-year period, as compared to normal birth weight infants. CONCLUSIONS: Rates of cesarean delivery among macrosomic infants continue to increase despite a lack of evidence of the benefits of cesarean delivery within this population. Further exploration of the rationale for this trend is warranted and should include the development of an optimal delivery strategy for such patients.

Cesarean Section↗
PubMed2005

Teen twin pregnancies: differences in fetal growth outcomes among blacks and whites.

We set out to determine the magnitude of black-white disparity in intrauterine fetal growth inhibition among twin births to teenagers (age 15 to 19) in the United States using a retrospective cohort study design. We compared the risk for low and very low birthweight, preterm and very preterm, and small for gestational age between black and white twins born to teen mothers during the period 1995 through 1998. The methodology of generalized estimating equations was used to adjust for the presence of intracluster correlation within twin pairs. A total of 29,307 individual twins were analyzed. For all fetal growth indices examined, infants born to black mothers remained disadvantaged except for preterm birth, for which the risk was comparable to that of whites (adjusted OR, 1.03; 95% confidence interval [CI] 0.95 to 1.11). The racial gap was most marked for low birthweight (OR, 1.27; 95% CI, 1.19, 1.37]) and very low birthweight (OR, 1.30; 95% CI, 1.19 to 1.42). Black twins had an equal level of elevated risk for very preterm and small for gestational age (OR, 1.17; 95% CI, 1.07 to 1.27 and OR, 1.17; 95% CI, 1.07 to 1.28, respectively). In conclusion, we found significant differences in fetal growth parameters between black and white twins born to teen gravidas. Our findings confirm similar black disadvantage reported for singletons. Current prevention strategies aimed at reducing adverse fetal outcomes among teenagers in the United States need to consider the heightened risk among neonates born to black mothers.

Adolescent↗