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A series of 1 wt% supported Au, Pd and AuPd nanoalloy catalysts were prepared via microwave assisted reduction of PdCl2 and HAuCl4 in a facile, one pot process. The resulting materials showed excellent activity for the direct synthesis of hydrogen peroxide from hydrogen and oxygen, with a synergistic effect observed on the addition of Au into a Pd catalyst. Detailed electron microscopy showed that the bimetallic particles exhibited a core-shell morphology, with an Au core surrounded by an Au-Pd shell, with a size between 10-20 nm. The presence of Au in the shell was confirmed by EDX studies, with corroborating data from XPS measurements showing a significant contribution of both Au and Pd in the spectra, with the Au signal increasing as the total Au content of the catalyst increased. No PdO was observed, suggesting a complete reduction of the metal chloride nanoparticles. Unlike similar catalysts prepared by sol-immobilisation methodology, the core-shell structures showed excellent stability during the hydrogen peroxide synthesis reaction, and no catalyst deactivation was observed over 4 reuse cycles. This is the first time the preparation of stable core-shell particles have been reported using microwave assisted reduction. The observation that these particles are core-shell, without the need of a complicated synthesis or high thermal treatment and form in just 15 minutes presents an exciting opportunity for this experimental technique.
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We demonstrate the ability to position single and multiple filaments arbitrarily within the energy reservoir of a high power femtosecond laser pulse. A deformable mirror controlled by a genetic algorithm finds the optimal phase profile for producing filaments at user-defined locations within the energy reservoir to within a quarter of the nominal filament size, on average. This proof-of-principle experiment demonstrates a potential technique for fast control of the configuration of the filaments.
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Intrathoracic desmoid tumours are rare soft-tissue neoplasms arising from fascial or musculo-aponeurotic structures, accounting for less than 0.03% of all neoplasms. Most cases in fact represent intrathoracic extension of chest wall tumours. This case report describes the largest recorded true intrathoracic desmoid tumour without mediastinal or chest wall invasion. The tumour was completely excised through a left thoracotomy with negative tumour margins. Management of the patient will involve radiological surveillance. Desmoids are benign tumours that do not metastasise but have a high rate of recurrence, especially if tumour margins are positive after surgical resection. Complete surgical resection is the treatment of choice. Other treatment options include radiotherapy; non-steroidal inflammatory drugs or antioestrogen therapy (tamoxifen) or a combination thereof; and chemotherapy or targeted drug therapy.
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Figs (Ficus) have a reciprocally obligate mutualism with tiny, short-lived (1-2 days) fig wasps (Agaonidae). The small size and short life of these pollinators is expected to make them more vulnerable to climate change than their larger and longer-lived hosts. We experimentally tested the thermal tolerances of four species of adult female fig wasp from equatorial Singapore. The results suggest that an increase of 3°C or more above the current temperatures experienced across much of the equatorial tropics would markedly decrease the active adult lifespan of all four species. Fig plants are the centre of an intricate web of specialist and generalist animals. Unless fig wasps can acclimate or adapt to warmer temperatures in time, these responses may disrupt the mutualism, potentially affecting multiple trophic levels.
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Extinción Biológica , Calentamiento Global , Polinización , Avispas/fisiología , AnimalesRESUMEN
Exposing and stabilizing undercoordinated platinum (Pt) sites and therefore optimizing their adsorption to reactive intermediates offers a desirable strategy to develop highly efficient Pt-based electrocatalysts. However, preparation of atomically controllable Pt-based model catalysts to understand the correlation between electronic structure, adsorption energy, and catalytic properties of atomic Pt sites is still challenging. Herein we report the atomically thin two-dimensional PtTe2 nanosheets with well-dispersed single atomic Te vacancies (Te-SAVs) and atomically well-defined undercoordinated Pt sites as a model electrocatalyst. A controlled thermal treatment drives the migration of the Te-SAVs to form thermodynamically stabilized, ordered Te-SAV clusters, which decreases both the density of states of undercoordinated Pt sites around the Fermi level and the interacting orbital volume of Pt sites. As a result, the binding strength of atomically defined Pt active sites to H intermediates is effectively reduced, which renders PtTe2 nanosheets highly active and stable in hydrogen evolution reaction.
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Harmonics up to the 18th order are generated from solid targets by focusing 2 mJ, 50 fs pulses at 800 nm to a spot size of 1.7 µm (FWHM). To our knowledge, this is the first demonstration of high-harmonic generation with a very short focal length paraboloid (f/1.4) and kilohertz laser system. The harmonics have a low divergence (<4°) compared to the driving beam and conversion efficiencies (>10(-7) per harmonic) comparable to gas harmonics. No contrast enhancement techniques are employed, and the system is capable of operating at 500 Hz.
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High intensity colliding laser pulses can create abundant electron-positron pair plasma [A. R. Bell and J. G. Kirk, Phys. Rev. Lett. 101, 200403 (2008)], which can scatter the incoming electromagnetic waves. This process can prevent one from reaching the critical field of quantum electrodynamics at which vacuum breakdown and polarization occur. Considering the pairs are seeded by the Schwinger mechanism, it is shown that the effects of radiation friction and the electron-positron avalanche development in vacuum depend on the electromagnetic wave polarization. For circularly polarized colliding pulses, these effects dominate not only the particle motion but also the evolution of the pulses. For linearly polarized pulses, these effects are not as strong. There is an apparent analogy of these cases with circular and linear electron accelerators to the corresponding constraining and reduced roles of synchrotron radiation losses.
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We investigate MeV-level attosecond electron bunches from ultrashort-pulse laser-solid interactions through similarities between experimental and simulated electron energy spectra. We show measurements of the bunch duration and temporal structure from particle-in-cell simulations. The experimental observation of such bunches favors specular reflection direction when focusing the laser pulse onto a subwavelength boundary of thick overdense plasmas at grazing incidence. Particle-in-cell simulation further reveals that the attosecond duration is a result of ultra-thin ([Formula: see text]tenth of a micron) gaps of zero electromagnetic energy density in the modulated reflected radiation, while the bunching (locally peaked electron concentration) comes from the highly-directional electron angular distribution acquired by the electrons in a grazing incidence setup. To isolate a single electron bunch, we perform simulations using 1-cycle laser pulses and analyze the effect of carrier-envelop phase with particle tracking. The duration of the electron bunch can be further decreased by increasing the laser intensity and the focal spot size, while its direction can be changed by tuning the preplasma density gradient.
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BACKGROUND: Studies of cancer incidence and early management will increasingly draw on routine electronic patient records. However, data may be incomplete or inaccurate. We developed a generalizable strategy for investigating presenting symptoms and delays in diagnosis using ovarian cancer as an example. METHODS: The General Practice Research Database was used to investigate the time between first report of symptom and diagnosis of 344 women diagnosed with ovarian cancer between 01/06/2002 and 31/05/2008. Effects of possible inaccuracies in dating of diagnosis on the frequencies and timing of the most commonly reported symptoms were investigated using four increasingly inclusive definitions of first diagnosis/suspicion: 1. "Definite diagnosis" 2. "Ambiguous diagnosis" 3. "First treatment or complication suggesting pre-existing diagnosis", 4 "First relevant test or referral". RESULTS: The most commonly coded symptoms before a definite diagnosis of ovarian cancer, were abdominal pain (41%), urogenital problems(25%), abdominal distension (24%), constipation/change in bowel habits (23%) with 70% of cases reporting at least one of these. The median time between first reporting each of these symptoms and diagnosis was 13, 21, 9.5 and 8.5 weeks respectively. 19% had a code for definitions 2 or 3 prior to definite diagnosis and 73% a code for 4. However, the proportion with symptoms and the delays were similar for all four definitions except 4, where the median delay was 8, 8, 3, 10 and 0 weeks respectively. CONCLUSION: Symptoms recorded in the General Practice Research Database are similar to those reported in the literature, although their frequency is lower than in studies based on self-report. Generalizable strategies for exploring the impact of recording practice on date of diagnosis in electronic patient records are recommended, and studies which date diagnoses in GP records need to present sensitivity analyses based on investigation, referral and diagnosis data. Free text information may be essential in obtaining accurate estimates of incidence, and for accurate dating of diagnoses.
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Neoplasias Ováricas/diagnóstico , Bases de Datos Factuales , Errores Diagnósticos , Medicina Familiar y Comunitaria/estadística & datos numéricos , Femenino , Control de Formularios y Registros/normas , Control de Formularios y Registros/estadística & datos numéricos , Humanos , Incidencia , Sistemas de Registros Médicos Computarizados , Neoplasias Ováricas/complicaciones , Neoplasias Ováricas/terapia , Atención Primaria de Salud , Sistema de Registros , Factores de Tiempo , Reino UnidoRESUMEN
BACKGROUND AND PURPOSE: Stereotactic ablative body radiotherapy for lung plans requires 4DCT. Most radiotherapy centres use this to determine an internal target volume (ITV), despite studies suggesting that planning on a mid-ventilation (Mid-V) phase can reduce target volumes. The purpose of this study is two-fold: to determine whether the Mid-V approach provides adequate coverage and to discuss methods to enable the Mid-V approach to be applied more widely. METHOD: 4D scans of 79 patients were outlined on every phase. The mid-V phase was identified. Margins were determined from the range of motion, and plans generated with a 55â¯Gy prescription. A grid-based method was used to get the probability of tumour coverage in the presence of systematic and random uncertainties, with and without blurring for breathing motion. RESULTS: For the Mid-V plans with the margins calculated from the van-Herk formula, after blurring doses for breathing, the coverage (dose covering 95% of the CTV 95% of the time) was greater than for plans with isotropic 5â¯mm margins uncorrected for breathing (58.2â¯Gy v 57.3â¯Gy). Similar results were obtained for a linear margin chosen as 0.15 of the breathing range. Deformable contour propagation in a commercial outlining system (ProSoma) identified the same mid-V phase in the majority of cases. CONCLUSION: Our results confirm that a mid-V approach can be used to reduce the PTV size, with no loss of tumour coverage. We propose the use of a simplified margin formula equal to the margin ignoring breathing plus 0.15 of the range of motion.
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Neoplasias Pulmonares/diagnóstico por imagen , Neoplasias Pulmonares/radioterapia , Radiocirugia/métodos , Planificación de la Radioterapia Asistida por Computador/métodos , Algoritmos , Tomografía Computarizada Cuatridimensional/métodos , Humanos , Imagenología Tridimensional/métodos , Neoplasias Pulmonares/fisiopatología , Dosificación Radioterapéutica , Mecánica RespiratoriaRESUMEN
The one-step vacuum carbonization synthesis of a platinum nano-catalyst embedded in a microporous heterocarbon (Pt@cPIM) is demonstrated. A nitrogen-rich polymer of an intrinsic microporosity (PIM) precursor is impregnated with PtCl62- to give (after vacuum carbonization at 700 °C) a nitrogen-containing heterocarbon with embedded Pt nanoparticles of typically 1â»4 nm diameter (with some particles up to 20 nm diameter). The Brunauer-Emmett-Teller (BET) surface area of this hybrid material is 518 m² g-1 (with a cumulative pore volume of 1.1 cm³ g-1) consistent with the surface area of the corresponding platinum-free heterocarbon. In electrochemical experiments, the heterocarbon-embedded nano-platinum is observed as reactive towards hydrogen oxidation, but essentially non-reactive towards bigger molecules during methanol oxidation or during oxygen reduction. Therefore, oxygen reduction under electrochemical conditions is suggested to occur mainly via a 2-electron pathway on the outer carbon shell to give H2O2. Kinetic selectivity is confirmed in exploratory catalysis experiments in the presence of H2 gas (which is oxidized on Pt) and O2 gas (which is reduced on the heterocarbon surface) to result in the direct formation of H2O2.
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OBJECTIVE: This study examines the maternal characteristics and birth outcomes of infants of U.S. resident Asian-Indian-American (AIA) mothers and compares those to infants of U.S. resident Whites and African-American (AA) mothers. METHODS: Single live births to U.S. resident mothers with race/ethnicity coded on birth certificate as AIA, non-Hispanic White, or non-Hispanic AA were drawn from NCHS 1995 to 2000 U.S. Linked Live Birth/Infant Death files. RESULTS: Compared to AAs or Whites, AIAs have the lowest percentage of births to teen or unmarried mothers and mothers with high parity for age or with low educational attainment. After taking these factors into account, AIA had the highest risk of LBW, small-for-gestational age and term SGA births but a risk of infant death only slightly higher than Whites and far less than AAs. CONCLUSIONS: The birth outcomes of AIAs do not follow the paradigm that more impoverished minority populations should have greater proportions of low birth weight and preterm births and accordingly greater infant mortality rates.
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Asiático/estadística & datos numéricos , Emigración e Inmigración/estadística & datos numéricos , Resultado del Embarazo/etnología , Resultado del Embarazo/epidemiología , Adolescente , Adulto , Negro o Afroamericano , Certificado de Nacimiento , Peso al Nacer , Femenino , Edad Gestacional , Humanos , India/etnología , Mortalidad Infantil , Recién Nacido de Bajo Peso , Recién Nacido , National Center for Health Statistics, U.S. , Embarazo , Nacimiento Prematuro , Estados Unidos/epidemiología , Población BlancaRESUMEN
Recent theory has demonstrated a novel physics regime for magnetic reconnection in high-energy-density plasmas where the magnetic field is advected by heat flux via the Nernst effect. Here we elucidate the physics of the electron dissipation layer in this regime. Through fully kinetic simulation and a generalized Ohm's law derived from first principles, we show that momentum transport due to a nonlocal effect, the heat-flux-viscosity, provides the dissipation mechanism for magnetic reconnection. Scaling analysis, and simulations show that the reconnection process comprises a magnetic field compression stage and quasisteady reconnection stage, and the characteristic width of the current sheet in this regime is several electron mean-free paths. These results show the important interplay between nonlocal transport effects and generation of anisotropic components to the distribution function.
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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.
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Articulaciones del Carpo/patología , Enfermedades de los Caballos/diagnóstico , Enfermedades de los Caballos/epidemiología , Cojera Animal/diagnóstico , Condicionamiento Físico Animal/efectos adversos , Animales , Huesos del Carpo/diagnóstico por imagen , Huesos del Carpo/patología , Articulaciones del Carpo/diagnóstico por imagen , Femenino , Miembro Anterior , Enfermedades de los Caballos/diagnóstico por imagen , Enfermedades de los Caballos/patología , Caballos , Cojera Animal/diagnóstico por imagen , Cojera Animal/epidemiología , Cojera Animal/patología , Masculino , Condicionamiento Físico Animal/métodos , Prevalencia , Radiografía , Factores de Riesgo , Esclerosis/diagnóstico , Esclerosis/diagnóstico por imagen , Esclerosis/epidemiología , Esclerosis/veterinaria , Índice de Severidad de la EnfermedadRESUMEN
The authors tested the hypothesis that people addicted to opiates manifest more psychopathology in areas that have been identified as predictors for high risk of suicidal behavior than do normal control subjects. They gave 278 patients in a methadone maintenance program and 207 normal control subjects the index of Potential Suicide (IPS), a scale designed to assess suicidal risk. Using discriminate function analysis, the authors found that 87% of 100 of the methadone patients and 98% of 100 of the normal control subjects were correctly identified on the basis of the IPS data.
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Opio , Conducta Social , Trastornos Relacionados con Sustancias/psicología , Suicidio , Adulto , Femenino , Humanos , Masculino , Metadona/uso terapéutico , Persona de Mediana Edad , Pruebas Psicológicas , Riesgo , Trastornos Relacionados con Sustancias/tratamiento farmacológico , Intento de SuicidioRESUMEN
OBJECTIVE: To explore the association between adequacy of prenatal care utilization and subsequent pediatric care utilization. DESIGN: A longitudinal follow-up of a nationally representative sample of infants born in 1988. PARTICIPANTS: Nine thousand four hundred forty women who had a live birth in 1988, and whose child was alive at the time of interview, and 8285 women from the original sample who were reinterviewed in 1991. MAIN OUTCOME MEASURE: There were four outcome measures: number of well-child visits; adequate immunization for diphtheria, tetanus, and pertussis; adequate immunization for polio; and continuity of a regular source of care, as measured by the number of sites for pediatric care. RESULTS: Children whose mothers had less than adequate prenatal care utilization had significantly fewer well-child visits, and were significantly less likely to have adequate immunizations, even after income, health insurance coverage, content of prenatal care, wantedness of child, sites of prenatal and pediatric care, and maternal and pregnancy risk characteristics were taken into account. Less than adequate prenatal care utilization was not associated with having more than one pediatric care site. CONCLUSIONS: Prenatal care utilization can be used to identify and target interventions to women who are at risk for not obtaining well-child care or complete immunizations for their children.
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Servicios de Salud del Niño/estadística & datos numéricos , Aceptación de la Atención de Salud/estadística & datos numéricos , Atención Prenatal/estadística & datos numéricos , Preescolar , Femenino , Estudios de Seguimiento , Humanos , Lactante , Recién Nacido , Estudios Longitudinales , Masculino , Embarazo , Vacunación/estadística & datos numéricosRESUMEN
Postnatal assessment of gestational age in preterm neonates traditionally has been performed using the methods of Dubowitz and Ballard. This study was designed to determine the accuracy of these methods in a sample of very low birth weight preterm neonates. Dubowitz and Ballard examinations were done on 110 preterm neonates within the first 72 hours of life by a neonatologist masked to the gestational age assessed antenatally. Mean birth weight was 1066 +/- 256 g (SD). These data were compared with gestational age assessments using last menstrual period and best obstetric estimate calculated by an obstetrician unaware of the neonatal examination. Mean gestational age using last menstrual period was 28.3 +/- 2.9 weeks. Mean differences between last menstrual period and Dubowitz/Ballard were -2.8 +/- 2.1 weeks and -2.6 +/- 2.2 weeks, respectively. Results using best obstetric estimate were similar. An ophthalmologist examined lens vessels of 89 neonates. A similar pattern toward overestimation of gestational age interval by Dubowitz/Ballard was seen at each lens vessel grade. The Dubowitz and Ballard examinations are inaccurate methods of assessing gestational age in preterm neonates with birth weights less than 1500 g.
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Edad Gestacional , Recién Nacido de Bajo Peso , Recien Nacido Prematuro , Peso al Nacer , Femenino , Humanos , Recién Nacido , Cristalino/crecimiento & desarrollo , MasculinoRESUMEN
Few authors have published investigations regarding a possible association between preeclampsia and changing paternity. This study employs an epidemiological approach to explore the relationship between severe preeclampsia and changes in paternity patterns among multigravidae in a Caribbean community (Guadeloupe, French West Indies). Multiparae who were diagnosed with preeclampsia or eclampsia with fetal complications (transfer of their infants in the Neonatal Department) and controls were examined (134 mothers' interviews). Information concerning paternity for the index and previous pregnancies was collected from three groups: women with pregnancy-induced hypertension (PIH); women with chronic hypertension (CH); and a control group consisting of women without hypertension during pregnancy. In 21/34 (61.7%) of PIH mothers, the father of the current pregnancy was different than that of the former, compared to 4/40 (10%) among CH and 10/60 (16.6%) in the controls (P < 0.0001). Moreover, considering three and four consecutive pregnancies, there was a significant trend (P < 0.005 and P < 0.02) for an increase in PIH with having a different father in each successive pregnancy. Patterns of changing paternity were significantly correlated with pregnancy-induced hypertension in multiparae but not with chronic hypertension and controls.
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Paternidad , Preeclampsia/etiología , Adulto , Femenino , Humanos , Hipertensión/etiología , Masculino , Paridad , Embarazo , Complicaciones Cardiovasculares del Embarazo/etiología , Análisis de Regresión , RiesgoRESUMEN
OBJECTIVE: To develop a current national fetal growth curve that can be used as a common reference point by researchers to facilitate investigations of the predictors and consequences of small and large for gestational age delivery. METHODS: Single live births to United States resident mothers in 1991 (n = 3,134,879) were used for the development of this curve, which was compared with four previously published fetal growth curves. Techniques were developed to address cases with implausible birth weight-gestational age combinations and to smooth fetal growth curves across gestational age categories. RESULTS: In general, the previously published fetal growth curves underestimated the 1991 United States reference curve. This underestimation is most apparent during the latter weeks of gestation, approximately 33-38 weeks. CONCLUSION: Our findings indicate that the prevalence of fetal growth restriction (FGR) will vary markedly, depending on the fetal growth curve used. Furthermore, many previously published fetal growth curves no longer provide an up-to-date reference for describing the distribution of birth weight by gestational age and for determining FGR that is consistent with the most recent live birth data for the entire United States.
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Desarrollo Embrionario y Fetal , Edad Gestacional , Humanos , Valores de Referencia , Estados UnidosRESUMEN
This study proposes a redesigned measure of prenatal care utilization based on modifications made to a preexisting index of the adequacy of such care. Six prenatal care utilization groups were delineated: intensive, adequate, intermediate, inadequate, no-care, and missing/unknown. Using 430,349 cases from South Carolina and North Carolina vital records from 1978 to 1982 (live birth-infant death cohort files for white resident mothers), this proposed prenatal care utilization measure was examined by maternal sociomedical risk characteristics (age-parity, marital status, education, complications of pregnancy, and previous pregnancy terminations) and by pregnancy outcomes (birth weight, gestational age, and birth weight- and gestational age-specific neonatal mortality). The intensive prenatal care group had relatively more pregnancy complications but also the most preferred pregnancy outcomes. Appreciable differences in birth weight and gestational age distributions were observed among the prenatal care categories within maternal risk status groups. Increased utilization of prenatal care was associated with higher mean birth weight and gestational age. However, after controlling for maternal risk status, an appreciable variation in birth weight- and gestational age-specific neonatal mortality was not apparent across prenatal care groups.