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Biomedical subjects

G R Alexander

Publications and source records attributed to G R Alexander.

At least 19 recordsLinked to original sources
PubMed2006

Clinical findings, diagnosis, prevalence and predisposing factors for lameness localised to the middle carpal joint in young Standardbred racehorses.

REASONS FOR PERFORMING STUDY: Lameness related to the middle carpal joint (MCJ) occurs in up to 30% of young Standardbred horses in race training and the incidence increase with radiographic severity of third carpal bone (C3) sclerosis on DPr-DDIO (skyline) view of the carpus. Factors predisposing horses to carpal injury have not been well investigated. OBJECTIVES: To determine the importance of MCJ lameness as a cause of wastage in young Standardbred racehorses, stage of training at which it occurs and predisposing factors, and to describe clinical findings and diagnosis. METHODS: Standardbred horses (n = 114) entering their first year of race training were examined at approximately 3-month intervals over 12-18 months. For 87 of the horses, a training diary was available and these horses were trained at 3 different stables, each using a different exercise regime. At each examination, forelimb conformation, MCJ effusion, MCJ lameness and radiographic findings were graded, and training history and reasons for lost training days recorded. Nuclear scintigraphy and exploratory arthroscopy were performed on a limited selection of horses. Results for horses that developed MCJ lameness during the study period were compared statistically with results for horses that did not. RESULTS: Carpal lameness occurred in 28% of horses and was present in 56% with forelimb lameness. In most cases lameness was mild, bilateral and with little or no MCJ effusion and was attributed to subchondral bone pain associated with radiographic evidence of C3 sclerosis. Carpal lameness was the most common reason for >1 month's rest during the study period. It occurred at any stage of training but, in most cases, some speed training had begun. Of the variables studied, poor forelimb conformation and more intense speed training were predisposing factors. CONCLUSIONS AND POTENTIAL RELEVANCE: The information gained should assist in making recommendations regarding training young Standardbreds to reduce the incidence of MCJ lameness. However, further investigations to determine the optimal training regime are warranted.

Animals↗
PubMed2005

Intrauterine tobacco smoke exposure and hyaline membrane disease amongst triplets.

We assessed the association between prenatal smoking and respiratory distress syndrome (RDS) among triplets using a population-based retrospective cohort of 12,169 triplet live births in the United States between 1995 and 1997. Analysis was conducted using the generalised estimating equation framework to adjust for intra-cluster correlations. A total of 938 cases of RDS were reported comprising 35 among smoking (7.2%) and 903 among non-smoking gravidas (7.7%). The likelihood of RDS was comparable in both smoking categories [adjusted odds ratio (OR) = 0.93; 95% confidence interval (CI) = 0.65-1.32]. The risk for RDS due to smoking diminished with declining birth weight albeit non-significantly: low birth weight (OR = 0.99; 95% CI = 0.40-2.42), very low birth weight (OR = 0.85; 95% CI = 0.39-1.86), and extremely low birth weight (OR = 0.69; 95% CI = 0.30-1.58). In conclusion, among triplet neonates, smoking during pregnancy was not associated with respiratory distress syndrome.

Birth Weight↗
PubMed2004

Mode of delivery and birth outcomes of macrosomic infants.

This review examines and summarises the literature regarding the mode of delivery of macrosomic infants and subsequent perinatal outcomes. A search of electronic databases was conducted and supplemented with investigation of the references cited in the original articles. Although the rates of obstetric complications differ among high birth weight infants delivered by caesarean section compared to those delivered vaginally, there is currently little evidence that perinatal mortality differs significantly by delivery method. Shoulder dystocia and birth injury occur with greater frequency among macrosomic infants, yet the relative inaccuracy of clinical and ultrasonographic estimates of birth weight among high birth weight infants indicates that a trial of labour may be warranted among non-diabetic mothers with a suspected macrosomic fetus. The majority of studies identified in this review utilised small sample sizes and observational design, thereby hindering valid assessments of the impact of delivery method on the mortality of this population. Consequently, an optimal management strategy has yet to be defined.

Birth Injuries↗
PubMed2004

Early mortality in twin pregnancies complicated by premature rupture of membranes in the United States.

There is little information on mortality among multiple gestations complicated by premature rupture of membranes (PROM). In this study, we estimated the occurrence of the components of early mortality (stillbirth, neonatal and infant mortality) among twin pregnancies using the generalised estimating equation framework to account for intra-cluster correlations. Using the population-attributable risk, we also computed the level of excess mortality that could be averted by preventing PROM. Our findings reveal that the likelihood of stillbirth (odds ratio (OR) = 1.88; 95% confidence interval (CI)=1.66-2.13), neonatal mortality (OR=3.45; 95% CI=3.18-3.74) and infant mortality (OR=3.26; 95% CI=3.03-3.50) was significantly higher among twin pregnancies exposed to PROM. Approximately 6% of all stillbirths, 15% of neonatal mortality and 14% of infant mortality among twins in the United States are attributable to PROM. We conclude that PROM is associated with an increased level of early mortality among twins.

Adult↗
PubMed2004

Use of free conjunctival grafts in horses: ten cases.

OBJECTIVE: To assess the effectiveness of free conjunctival grafts in the treatment of horses with a range of keratopathies. DESIGN: A retrospective clinical study of ten client-owned horses treated at Murdoch University Veterinary Hospital from May 1996 to September 2001. PROCEDURE: The suitability of patients for the surgical procedure was assessed using a slit lamp biomicroscope and by direct and indirect ophthalmoscopy. Surgery was performed with the aid of an operating microscope, under general anaesthesia. A subpalpebral ocular lavage catheter was used for administration of topical atropine and antibiotics postoperatively. RESULTS: In all ten horses the affected globe was saved. In nine of the horses vision in the eye was satisfactory 6 months after surgery, and in one horse the eye was blind. Complications included further corneal ulceration or eyelid abscessation and some loss of sutures, although these did not preclude a successful outcome. CONCLUSION: Free conjunctival grafts were successful in treating a range of keratopathies in the horse, and the technique offers a number of advantages over other forms of surgical intervention.

Animals↗
PubMed2004

Radiographic evaluation of sclerosis of the third carpal bone associated with exercise and the development of lameness in Standardbred racehorses.

REASONS FOR PERFORMING STUDY: Sclerosis of the third carpal bone is a common radiographic finding in both lame and sound racehorses, but there are no guidelines correlating degree of sclerosis and incidence of lameness. OBJECTIVES: To develop a protocol for describing subchondral bone sclerosis in C3 on dorsoproximal-dorsodistal oblique (DPr-DDiO) radiographs of the carpus and to correlate these changes with exercise history and carpal lameness. METHODS: One hundred and six Standardbreds entering their first year of training (exercise group) and 7 age-matched Standardbreds at pasture (controls) were examined at approximately 3 month intervals over 12-18 months. Examinations consisted of lameness evaluation and carpal radiographs (DPr-DDiO and flexed lateromedial projections). A grading system (very mild, mild, moderate and severe) for C3 sclerosis seen on the DPr-DDiO radiograph was developed that utilised a combination of the criteria of trabecular thickening (trabecular score; TS) and total percent area of the C3 radial facet affected (TAA). RESULTS: Exercise group horses showed significant increase in TS and TAA throughout training compared to control horses. Middle carpal joint lameness developed in 32/106 (30%) exercise group horses and none of the control horses. Incidence of middle carpal joint (MCJ) lameness was lower in horses with mild (2/30, 6.7%) than moderate (10/32, 31.2%) and severe (20/44, 45.4%) sclerosis throughout training. CONCLUSIONS: Horses with higher grades of sclerosis, as defined by this novel grading system, were more likely to develop MCJ lameness at some point of training. The proposed grading system gave a quantitative assessment of radiographic sclerosis that could then be used to correlate increasing severity of sclerosis with increasing incidences of lameness. POTENTIAL RELEVANCE: These results serve as a basis for further investigation into determining the degree of C3 sclerosis at which pathological changes and lameness can be expected.

Animals↗
PubMed2003

Preventing low birth weight: is prenatal care the answer?

OBJECTIVES: To review the evidence of effectiveness of prenatal care for preventing low birth weight (LBW). METHODS: We reviewed original research, systematic reviews, meta-analyses and commentaries for evidence of effectiveness of the three core components of prenatal care--risk assessment, health promotion and medical and psychosocial interventions--for preventing the two constituents of LBW: preterm birth and intrauterine growth restriction (IUGR). RESULTS: Clinical risk assessment will fail to identify the majority of pregnancies at risk for preterm delivery or IUGR. While biophysical and biochemical modalities appear promising, their cost-effectiveness has not been demonstrated, nor can their routine use be recommended in the absence of effective interventions. Smoking cessation programs appear to be modestly effective. There is insufficient evidence to conclude a benefit for nutrition interventions, work counseling or preterm birth education. Only antenatal corticosteroid therapy has demonstrated a clear benefit in the tertiary prevention of preterm delivery. Interventions for which there is insufficient evidence to conclude a benefit include bed rest, hydration, sedation, cerclage, progesterone supplementation, antibiotic treatment, tocolysis without concomitant use of corticosteroids, thyrotropin-releasing hormone, psychosocial support and home visitation. Additionally, there is a paucity of evidence supporting the effectiveness of prenatal interventions, such as low-dose aspirin, bed rest, maternal hyperoxygenation, plasma volume expansion and antenatal fetal assessment, in preventing IUGR or its associated morbidity and mortality. CONCLUSIONS: Neither preterm birth nor IUGR can be effectively prevented by prenatal care in its present form. Preventing LBW will require reconceptualization of prenatal care as part of a longitudinally and contextually integrated strategy to promote optimal development of women's reproductive health not only during pregnancy, but over the life course.

Female↗
PubMed2002

Non-surgical management of rectal tears in two mares.

Two mares presented with life-threatening rectal tears were successfully treated with intensive medical management. Although surgery has been regarded as mandatory for grade 3 or 4 rectal tears in the past, recent reports have indicated the value of medical management alone. The case reports presented in this article detail the use of antibiotics, flunixin meglumine, laxative diets and faecal softeners in the medical management of two mares presented with grade 3 rectal tears.

Animals↗
PubMed2001

Trends in preterm birth and neonatal mortality among blacks and whites in the United States from 1989 to 1997.

Preterm birth, a major determinant of infant mortality, has been increasing in recent years. The authors examined trends in preterm birth and its determinants by using the US birth and infant death files for 1989-1997. The impact of trends in preterm birth rates on neonatal and infant mortality was also evaluated. Among Whites, preterm births (<37 completed weeks of gestation) increased from 8.8% of livebirths in 1989 to 10.2% in 1997, a relative increase of 15.6%. On the other hand, preterm births among Blacks decreased by 7.6% (from 19.0% to 17.5%) during the same period. An increase in obstetric interventions contributed to increases in preterm births for both races but was outweighed by other unidentified favorable influences for Blacks. Neonatal mortality among preterm Whites dropped 34% during the 8 years of the study, while the decrease was only 24% among Blacks. This large disparity countered the changes in preterm birth rates so that the percentage decline in neonatal mortality was similar in the two racial groups (18-20%). In conclusion, the anticipated mortality benefit from a lower preterm birth rate for Blacks has been blunted by suboptimal improvement in mortality among the remaining preterm infants. The widening race gap in mortality among preterm infants merits attention.

Black or African American↗
PubMed2001

Prenatal care use among selected Asian American groups.

OBJECTIVES: This study examined the predictors of 3 patterns of prenatal care use (no care, late initiation of care, and inadequate use after early initiation) for 4 Asian American ethnic groups in the United States. METHODS: Single live births to US resident mothers of Chinese, Japanese, Korean, and Vietnamese ancestry (n = 273 604) were selected from the 1992-1996 US natality files. Logistic regression was used to analyze the effects of maternal characteristics on the 3 use measures. RESULTS: Korean Americans and Vietnamese Americans had the lowest levels of prenatal care use. Young or single motherhood, high parity for age, and low educational attainment were the main risk factors for low use. CONCLUSIONS: Considerable variability exists in prenatal care use among Asian American ethnic groups.

Adolescent↗
PubMed2000

Trends in twin birth outcomes and prenatal care utilization in the United States, 1981-1997.

CONTEXT: Multiple births account for an increasing percentage of all low-birth-weight infants, preterm births, and infant mortality in the United States. Since 1981, the percentage of women with multiple births who received intensive prenatal care (defined as a high number of visits, exceeding the recommendation of the American College of Obstetricians and Gynecologists by approximately 1 SD beyond the mean number of visits for women initiating care within each trimester) has increased significantly. OBJECTIVES: To explore the hypothesis that more aggressive management of twin-birth pregnancies may be associated with changes in birth outcomes in this population. DESIGN, SETTING, AND SUBJECTS: Cross-sectional and trend analysis of data from the National Center for Health Statistics' birth and infant death records for all twin births occurring in the United States between 1981 and 1997, excluding those with missing or inconsistent data. MAIN OUTCOME MEASURES: Trends in preterm birth, low birth weight, preterm and term small-for-gestational-age (SGA) births, and infant mortality, by level of prenatal care utilization. RESULTS: The preterm birth rate for twins increased from 40.9% in 1981 to 55.0% in 1997. The percentage of low-birth-weight infants increased from 51.0% to 54.0%. The preterm SGA rate also increased from 11.9% to 14.1%, while the term SGA rate decreased from 30.7% to 20.5%. For women with intensive prenatal care utilization, the preterm birth rate increased from 35.1% to 55.8%, compared with an increase from 50.6% to 59.2% among women with only adequate use. Twin preterm deliveries involving either induction or first cesarean delivery also increased from 21.9% to 27.3% between 1989-1991 and 1995-1997. The twin infant mortality rate for women with intensive prenatal care use declined between 1983 and 1996 and remained lower than the overall twin infant mortality rate. CONCLUSIONS: An apparent increase in medical interventions in the management of twins may result in the seeming incongruity of more prenatal care and more preterm births; however, these data suggest that women with intensive prenatal care utilization also have a lower infant mortality rate. JAMA. 2000;283:335-341

Cross-Sectional Studies↗
PubMed2000

Racial differences in temporal changes in newborn viability and survival by gestational age.

This study examines trends in the rates of very preterm, moderately preterm and gestational age-specific neonatal mortality, and in the gestational age limit of viability in South Carolina (SC) from 1975 to 1994. We also investigate whether trends were similar between African-Americans and Whites. We hypothesised that disproportionate reductions in gestational age-specific mortality, rather than any major changes in the gestational age distributions of either race group, underlie any increasing racial disparity in overall mortality rates. During 1975-94, single livebirths, who were born to mothers resident in SC and were either White or African-American based on recorded maternal race, were selected for the investigation. We define the gestational age limit of viability as the gestational age at which > or = 50% of infants in the population died within 28 days of life. Although preterm percentages have not improved, there was a marked decline in neonatal mortality. Gestational age-specific neonatal mortality decreased for both race groups, although there were greater reductions for White preterm infants. By the end of the study period, the African-American neonatal mortality rate was 2.3 times that of Whites and the gestational age at which 50% of newborns died within 28 days of life was 24.5 weeks for Whites and 23.9 weeks for African-Americans. The ongoing decline in neonatal mortality continues to be mainly due to reductions in gestational age-specific neonatal mortality, probably related to high-risk obstetric and neonatal care. Technological developments in these areas may have differentially benefited Whites, resulting in an increasing racial disparity in neonatal mortality rates. Preterm African-American infants no longer have a marked survival advantage over White infants, even at the gestational age limit of viability.

Black or African American↗
PubMed1999

Trends and racial differences in birth weight and related survival.

OBJECTIVE: In the past two decades, infant mortality rates in the United States declined in African-American and White populations. Despite this, racial disparities in infant mortality rates have increased and rates of low birth weight deliveries have shown little change. In this study, we examine temporal changes in birth weight distributions, birth weight specific neonatal mortality, and the birth weight threshold for an adverse risk of survival within both racial groups in order to explore the mechanisms for the disparities in infant mortality rates. METHOD: Single live births born to South Carolina resident mothers between 1975 and 1994 and considered White or African-American based on the mother's report of maternal race on the birth certificate were selected for investigation. We define the birth weight threshold for adverse survival odds as the birth weight at which 50% or more of infants in the population died within the first month of life. RESULTS: Despite significant increases in very low birth weight percentages, neonatal mortality rates markedly declined. Birth weight specific neonatal mortality decreased for both races, although greater reductions accrued to White low birth weight infants. By the end of the study period, the birth weight at which over 50% of newborns died within the first month of life was 696 g for Whites and 673 g for African-Americans. DISCUSSION: The ongoing decline in neonatal mortality is mainly due to reductions in birth weight specific neonatal mortality, probably related to high-risk obstetric and neonatal care. Technological developments in these areas may have differentially benefited Whites, resulting in an increasing racial disparity in mortality rates. Moreover, the relatively greater and increasing mortality risk from postmaturity and macrosomia in infants of African-America mothers may further exacerbate the racial gap in infant mortality.

Female↗
PubMed1999

1994-1996 U.S. singleton birth weight percentiles for gestational age by race, Hispanic origin, and gender.

OBJECTIVES: Establishing and comparing race, ethnic, and gender-specific birth weight percentiles for gestational age is requisite for investigating the determinants of variations in fetal growth. In this study, we calculate percentiles of birth weight for gestational age for the total 1994-1996 U.S. population and contrast these percentiles by racial/ethnic and gender groups. METHODS: Single live births to U.S. resident mothers were selected from the 1994-1996 U.S. Natality Files. After exclusions, 5,973,440 non-Hispanic Whites, 1,393,908 non-Hispanic African Americans, 1,683,333 Hispanics, 80,187 Native Americans, and 510,021 other racial/ethnic groups were used to calculate distribution percentiles of birth weight for each gestational age for which there were at least 50 cases to calculate the 50th percentile and 100 cases to calculate the 10th percentile. RESULTS: Fetal growth patterns among the four U.S. racial/ethnic groups varied markedly and, across the gestational age range, there was considerable oscillation in the relative ranking of any one group's birth weight percentile value in comparison to the others. Males had relatively higher birth weight percentile values than females. The proportion of infants with a birth weight value less than 1994-1996 U.S. population's 10th percentile value of birth weight for their corresponding gestational age was 7.87 for non-Hispanic Whites, 15.43 for non-Hispanic African Americans, 9.30 for Hispanics, and 8.81 for Native Americans. CONCLUSIONS: While the factors underlying trends and population subgroup differences in fetal growth are unclear, nutrition, smoking habits, health status, and maternal morbidity are possible precursors for part of the variations in patterns of fetal growth. As prenatal care has been touted as a means to reduce the risk of fetal growth restriction at term, assuring the availability and accessibility of comprehensive prenatal care services is viewed as an essential corollary in the effort to improve fetal growth patterns in the United States.

Black or African American↗
PubMed1999

Racial differences in birthweight for gestational age and infant mortality in extremely-low-risk US populations.

Using national data, we develop and contrast the birth-weight percentiles for gestational age by infants of extremely-low-risk (ELR) White and African-American women and examine racial differences in the proportion of small-for-gestational-age (SGA) births. We then scrutinise racial variations in infant mortality rates of the infants of ELR women. We further compare the infant mortality rates of infants at or below the 10th percentile of birthweight for gestational age of each race group to determine whether infants with similar restricted fetal growth have comparable risks of subsequent mortality. Single live births, 34-42 weeks' gestation, to White and African-American US-resident mothers were selected from the 1990-91 US Linked Live Birth--Infant Death File (n = 4,360,829). Extremely-low-risk mothers were defined as: married, aged 20-34 years, 13+ years of education, multiparae, with average parity for age, adequate prenatal care, vaginal delivery, and no reports of medical risk factors, tobacco use or alcohol use during pregnancy. Marked racial variation in birthweight percentiles by gestational age was evident. Compared with ELR White mothers, the risk of an SGA infant was 2.64 times greater for ELR African-American mothers and the risk of infant mortality was 1.61 times greater. For the ELR group, the infant mortality rates of African-American and White infants at or below the 10th percentile of birthweight for gestational age of their respective maternal race group were essentially identical after controlling for gestational age. In conclusion, race differences in fetal growth patterns remained after controlling for risk status. Efforts to remove racial disparities in infant mortality will need to develop aetiological pathways that can explain why African-Americans have relatively higher rates of preterm birth and higher infant mortality rates among term and non-SGA infants.

Adult↗
PubMed1999

Changing pregnancy outcomes of Samoan women in Hawaii.

In the state of Hawaii, Samoan mothers are known for the large average birthweight and low percentage of low birthweight (< 2500 g) of their infants, in spite of the relatively low socio-economic status of the population. This paper reports the findings of a temporal trend analysis of birth outcomes of Samoan women and identifies worrying changes. Data were obtained from Hawaii birth certificates. Single live births to Hawaii-resident Samoan and Caucasian women from 1979 to 1994 were included in the study. Infants of Samoan women experienced a 75 g decline in mean birthweight and an increase in the percentage of low (< 2500 g) and very low (< 1500 g) birthweight from 2.6 and 0.4 to 3.8 and 0.8 respectively. During the same time, infants of Caucasian mothers experienced an increase in mean birthweight and a decline in low birthweight, while very low birthweight did not change. Maternal socio-demographic characteristics explained only part of the findings and use of prenatal care did not appear to be associated with any birth outcome indicators. Multiple regression analyses identified an adjusted loss of 50.8 g in birthweight and a 1.48 increase in the odds ratio of small-for-gestational-age associated with birth at the end (1991-4) compared with the beginning (1979-82) of the study period. Further studies focusing on maternal health status and psycho-social variables, including the effect of acculturation-related stress, are warranted to identify at least some of the determinants of the changes identified by this analysis.

Adolescent↗
PubMed1998

Influence of diabetes during pregnancy on gestational age-specific newborn weight among US black and US white infants.

This study examined the impact of maternal diabetes on birth weight for gestational age patterns of all term black infants and white infants in the United States using data derived from the 1990-1991 US Live Birth File of the National Center for Health Statistics. Infants of both black mothers and white mothers exhibited the expected fetal overgrowth associated with maternal diabetes. However, the increase in birth weight was much greater in infants of black than white diabetic mothers in comparison with their nondiabetic counterparts, as measured by the discrepancy in birth weight between infants of diabetic and nondiabetic mothers at each gestational week, the incidence of large for gestational age, high birth weight, small for gestational age, and low birth weight. After adjustment for maternal hypertension, prenatal care use, and sociodemographic factors, the disparity in mean birth weight associated with diabetes was 211.67 g in black infants and 115.74 g in white infants. The adjusted odds ratios of birth weight > or = 4,000 g were 2.98 (95% confidence interval 2.89-3.12) for black infants and 1.83 (95% confidence interval 1.78-1.89) for white infants. Given the potential risks for mothers and infants consequent to maternal diabetes and fetal hyperinsulinemia, further investigation of the prevalence, characteristics, and outcomes of diabetes during pregnancy among black mothers and infants is warranted.

Adult↗