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Biomedical subjects

B Blondel

Publications and source records attributed to B Blondel.

At least 37 records · Page 2Linked to original sources
PubMed2001

Detecting and eliminating erroneous gestational ages: a normal mixture model.

In perinatal research and clinical practice, gestational age is a crucial variable for measuring foetal 'growth' (birth weight for gestational age) and for estimating the risk of mortality and morbidity, yet reported gestational age values are affected by random and systematic errors due to the absence of a gold standard measure. Previous investigators have used birth weight (which is measured with greater validity and precision than is gestational age) to correct such errors, but existing methods are inadequate due to unreasonable assumptions about the distributions of birth weight and gestational age. We propose a new method for identifying and correcting implausible observations using the expectation-maximization (EM) algorithm. Using population-based data from U.S. birth certificates, we compare the resulting gestational ages, birth weight distributions at each gestational age, and gestational age-specific infant mortality based on the new method with those on the same population produced by previous published correction methods. The new method gives the best birth weight distributions for gestational age and the most realistic gestational-age-specific mortality rates, while each of the other methods has at least one significant flaw.

Algorithms↗
PubMed2001

Antenatal care in Europe: varying ways of providing high-coverage services.

OBJECTIVES: To describe the organizational characteristics of antenatal care and their relation to the utilization of health services and perinatal mortality in 13 European countries. METHODS: The main data source was a questionnaire on the organization and financing of antenatal care, filled out in 1995 by country representatives of a European Concerted Action. RESULTS: Thirteen systems for providing antenatal care were found. No clear grouping by organizational characteristics (uniformity, main care providers, integration, continuity of care, physical site, financing) emerged. Organizational characteristics and the utilization of antenatal services or perinatal mortality did not relate to each other. CONCLUSIONS: There is no single way to provide high-coverage services. Further studies are needed to relate organization characteristics to health impact, costs, and patient satisfaction.

Delivery of Health Care↗
PubMed2001

Trends in risk factors for caesarean sections in France between 1981 and 1995: lessons for reducing the rates in the future.

OBJECTIVE: To assess the effects of the characteristics of mothers, fetuses and maternity units on the trends in caesarean section use, especially for primiparae. DESIGN: Cross sectional surveys. SETTING: Maternity units. POPULATION: Two representative national samples of births including 5410 newborns in 1981 and 13318 in 1995. METHOD: Univariate analysis and logistic regression analysis. RESULTS: The overall rate of caesarean section rose from 10.7% in 1981 to 15.3% in 1995. This trend is mainly attributable to the increases in the proportion of previously sectioned women (from 4.1% to 8.2%) and in caesarean sections for primiparae (from 12.6% to 17.8%). Among primiparae several maternal risk factors such as late childbearing and obesity before pregnancy were more frequent in 1995 than in 1981. The increase in caesarean sections affected both the high risk group (25.4% to 32.4%) and the low risk group (8.1% to 12.0%). CONCLUSION: A significant reduction in the overall rate cannot be achieved without regulating caesarean section use for primiparae. Strategies to change delivery patterns should be aimed at both high and low risk women.

Adult↗
PubMed2001

Comparability of published perinatal mortality rates in Western Europe: the quantitative impact of differences in gestational age and birthweight criteria.

OBJECTIVE: To quantify the impact of publication criteria on differences in published national perinatal mortality rates among Western European countries. DESIGN: Descriptive study of perinatal mortality rates in Western European countries with adjustments for international differences in publication data. POPULATION: All live births and perinatal deaths in 1994 in Western European countries. METHODS: The 1994 perinatal mortality rates were obtained from national and Eurostat publications for Belgium, Denmark, Finland, France, Germany, Greece, The Netherlands. Norway, Portugal, Spain, Sweden, United Kingdom (England, Wales, Scotland, Northern Ireland). Two methods, one direct and one indirect, were used for adjusting these officially published rates for differences in registration laws or publication practices. For the indirect method adjustment factors were derived from an analysis of a large Finnish database using different cutoff points for gestational age and birthweight. For the direct method a common cutoff point was imposed for birthweight (1000g) and gestational age (28 completed weeks) on national perinatal mortality data, obtained from civil registration or hospital/obstetrics databases in each country. RESULTS: The published perinatal mortality rates ranged from 5.4 per 1000 total births in Sweden and Finland to 9.7 in Greece and Northern Ireland. The indirect adjustment method showed that some countries apply cutoff points for registration or publication of perinatal mortality which may raise the perinatal mortality rate by up to 17% above the most commonly used threshold for including live and stillbirths. The direct adjustment method showed that a common lower limit of 1000g for birthweight or 28 weeks for gestational age would reduce the perinatal mortality rate, but by a differing extent ranging from 14% to 40%. Both adjustment methods reduced the contrast between the countries' perinatal mortality rates, and changed their rank order. CONCLUSION: These quantitative results confirm that international differences in countries' published perinatal mortality rates partly reflect differences between countries' criteria for registration and publication of perinatal deaths.

Birth Weight↗
PubMed2001

A new and improved population-based Canadian reference for birth weight for gestational age.

BACKGROUND: Existing fetal growth references all suffer from 1 or more major methodologic problems, including errors in reported gestational age, biologically implausible birth weight for gestational age, insufficient sample sizes at low gestational age, single-hospital or other non-population-based samples, and inadequate statistical modeling techniques. METHODS: We used the newly developed Canadian national linked file of singleton births and infant deaths for births between 1994 and 1996, for which gestational age is largely based on early ultrasound estimates. Assuming a normal distribution for birth weight at each gestational age, we used the expectation-maximization algorithm to exclude infants with gestational ages that were more consistent with 40-week births than with the observed gestational age. Distributions of birth weight at the corrected gestational ages were then statistically smoothed. RESULTS: The resulting male and female curves provide smooth and biologically plausible means, standard deviations, and percentile cutoffs for defining small- and large-for-gestational-age births. Large-for-gestational age cutoffs (90th percentile) at low gestational ages are considerably lower than those of existing references, whereas small-for-gestational-age cutoffs (10th percentile) postterm are higher. For example, compared with the current World Health Organization reference from California (Williams et al, 1982) and a recently proposed US national reference (Alexander et al, 1996), the 90th percentiles for singleton males at 30 weeks are 1837 versus 2159 and 2710 g. The corresponding 10th percentiles at 42 weeks are 3233 versus 3086 and 2998 g. CONCLUSIONS: This new sex-specific, population-based reference should improve clinical assessment of growth in individual newborns, population-based surveillance of geographic and temporal trends in birth weight for gestational age, and evaluation of clinical or public health interventions to enhance fetal growth. fetal growth, birth weight, gestational age, preterm birth, postterm birth.

Algorithms↗
PubMed2001

Development and behaviour of seven-year-old triplets.

UNLABELLED: The aim of this study was to assess the development and behaviour of 7-y-old triplets, who were followed from delivery to 7 y of age. The McCarthy Scales of Children's Abilities (MSCA) and Achenbach's Child Behaviour Checklist (CBCL) were used to assess and compare development and behaviour in the triplets and in a control group of singletons. The sample included 33 sets of triplets and 33 singletons, all 7-y-olds, and comparable for sex and fathers' social class. The triplets' scores on the MSCA were all within normal range. Although their mean scores for all subtests were below those of singletons, they did not differ significantly. The mean CBCL scores, based on mothers' reports, indicated that the triplets had significantly fewer behavioural problems than the controls. In half the triplet sets, one child stood out as having more behavioural problems than the others. CONCLUSION: Further assessments of the development of triplets are needed; these should be based on larger study samples and should use information from teachers and external observers as well as mothers.

Chi-Square Distribution↗
PubMed2001

[Factors associated with cesarean section in France. Results from the 1995 National Perinatal Survey].

OBJECTIVE: to study the relationship between the cesarean section rates and the characteristics of newborns, mothers and maternity units, studying primary and repeat cesarean sections, and cesarean sections before and during labour separately. Population. Representative sample of births in France. METHOD: Univariate and multivariate analyses. RESULTS: The primary cesarean section rate (among women without previous cesarean section) was 11.0% and the repeat cesarean section rate was 62.9%. The main factors associated with primary cesarean sections were breech presentation, small-for-gestational age before term, and high birthweight, for characteristics of newborns, and parity 0,30 years old or more and high pre- pregnancy weight, for characteristics of mothers. These factors were linked to cesarean sections before labour and during labour. Preterm and post-term deliveries, educational level, and nationality played a different role before and during labour. Very few factors were linked to repeat cesarean sections. CONCLUSION: Various factors are associated with cesarean sections; they express the influence of both unfavorable medical conditions and particular medical care organisations.

Adult↗
PubMed2001

Inhibition of poliovirus RNA synthesis as a molecular mechanism contributing to viral persistence in the mouse central nervous system.

Many survivors of poliomyelitis, several decades after the acute phase of the disease, develop a set of new muscle symptoms called post-polio syndrome. The persistence of poliovirus (PV) in the central nervous system (CNS) may be involved in the aetiology of this syndrome. By using a mouse model, we have shown that PV persists in the CNS of paralysed mice for over a year after the acute disease. Detection of PV plus- and minus-strand RNAs in the spinal cord of paralysed mice suggested continuous PV RNA replication in the CNS. However, infectious PV particles could not be recovered from homogenates of CNS from paralysed mice beyond 20 days post-paralysis, indicating that PV replication was restricted. In an attempt to identify the molecular mechanism by which PV replication was limited, PV plus- and minus-strand RNA levels were estimated in the CNS of persistently infected mice by a semi-quantitative RT-nested PCR method. Results revealed that RNA replication was inhibited at the level of plus-strand RNA synthesis during persistent infection. Similar results were obtained in neuroblastoma IMR-32 cell cultures persistently infected with PV Restriction of PV RNA synthesis could be involved in persistence by limiting PV replication.

Animals↗
PubMed2001

Poliovirus persistence in human cells in vitro.

Poliovirus (PV) can persist in vivo in the intestine of immunocompromised hosts for years. Moreover, immunocompetent individuals who have survived paralytic poliomyelitis sometimes develop the post-poliomyelitis syndrome (PPS), consisting of a variety of symptoms including new muscular atrophies. PPS may be due to PV persistence. We have developed models of PV persistence in neural cells and epidermoid cells. Cell determinants are of crucial importance for the establishment of persistent infections in human neuronal cells, whereas viral determinants play the primary role in human epidermoid HEp-2 cells. The results obtained with these in vitro models show the capacity of PV to persist and reveal a virus and cell co-evolution involving PV-receptor interactions. In addition, they suggest that several mechanisms are used by PV to establish and maintain persistent infections.

Animals↗
PubMed2001

[Development of the main indicators of perinatal health in metropolitan France between 1995 and 1998. Results of the national perinatal survey].

OBJECTIVE: To study trends in the main indicators of health, medical practice and risk factors. POPULATION AND METHOD: We compared two samples; both included all stillbirths and live births during one week in France: 13,318 in 1995 and 13,718 in 1998. RESULTS: Between 1995 and 1998, there was an increase in maternal age, a development of some characteristics of care (antenatal care by maternity unit staff, HIV screening procedure, antenatal classes) and an increase in the proportion of caesarean sections and epidurals. The proportion of live births before 37 weeks of gestation increased from 5.4% to 6.2%. This trend is explained by an increase in preterm deliveries among twins. Specific questions in the 1998 questionnaire showed that 6.3% of women had received fertility treatment before this pregnancy, 11.1% had an amniocentesis, and 1.1% had an intrauterine transfer. CONCLUSION: This type of survey carried out every three years can show major changes in health, risk factors and medical practices and can yield quick answers to specific questions.

Adult↗
PubMed2000

Expression of mutated poliovirus receptors in human neuroblastoma cells persistently infected with poliovirus.

Poliovirus (PV) is able to establish persistent infections in human neuroblastoma IMR-32 cells [Colbère-Garapin et al. (1989) Proc. Natl. Acad. Sci. USA 86, 7590]. During persistent infection, PV mutants are selected that display substitutions of residues in regions of the capsid known to interact with the PV receptor (PVR), a glycoprotein of the immunoglobulin superfamily. The mechanism of persistent infection in IMR-32 cells may therefore involve the selection of mutant PVRs. To test this hypothesis, the sequences of the PVR mRNAs in uninfected IMR-32 cells and in two independent IMR-32 cell cultures persistently infected with the Mahoney strain of PV type 1 (PV1/Mahoney) were determined. The PVR mRNA population of uninfected cells was homogeneous, and no mutation was repeatedly found, whereas that of persistently infected cells displayed missense mutations. Particular mutations were repeatedly detected, and all of them mapped to the N-terminal domain of PVR (domain 1), which interacts directly with PV. These mutations generated several types of PVR variants with the following substitutions: Ala67-->Thr alone, Ala67-->Thr associated with Gly39-->Ser, and Arg104-->Gln. Functional analysis of PVR in murine LM cells, stably expressing each of the PVR forms, showed that the PVR forms selected during persistent infection conferred on LM cells partial resistance to PV1/Mahoney-induced lysis. Although adsorption onto PVR seemed to be independent of the PVR form, an analysis of the conformational changes of the capsid during the early steps of the PV cycle provided evidence that the Ser39/Thr67 and Gln104 substitutions almost halved the conversion of 160S infectious particles into 135S A particles associated with the PV-PVR interaction. Altogether, these findings indicate that during persistent infection, specific mutations were selected in the domain 1 of PVR and that these mutations increased the resistance of cells to PV-induced lysis. These results are discussed in view of the position of the mutations on PVR.

Amino Acid Substitution↗
PubMed2000

[Trends in infant mortality in France: frequency and causes from 1950 to 1997].

OBJECTIVES: To present an analysis of the infant mortality trends and causes of death in France from the beginning of the 1950s, neonatal (0-27 days) and post-neonatal mortality (27-364 days) being considered separately. MATERIAL AND METHODS: We used the data from the national registries of births computed by INSEE (National Institute of Statistics and Economic Surveys) and of causes of deaths computed by Inserm (National Institute of Health and Medical Research). We analysed the evolution of the infant death rates from 1950 to 1997, the overall mortality for males and the percentages of causes of death at three different periods. RESULTS: Mortality has changed according to neonatal or post-neonatal ages. A constant improvement was recorded for neonatal mortality up to 1995 (2.9 per 1,000), while there was a stagnation for post-neonatal mortality between 1979 and 1993, followed by a sharp decrease (2.0 per 1,000 in 1995). During the neonatal age the main causes of death are conditions generated in the neonatal period and congenital abnormalities, both decreasing regularly; during the post-neonatal age the main cause is sudden infant death syndrome, which fell dramatically during the last four years. CONCLUSION: Several factors related to medical care, nursing and type of registration are contributing simultaneously to the important variations in mortality found in our results.

Cause of Death↗
PubMed2000

[Mothers of triplets and their children: course from 4 to 7 years after birth].

OBJECTIVES: To study the psychological health of the mothers and their difficulties seven years after the birth of triplets and to compare these results with those obtained at four years. DATA AND METHODS: Eleven mothers of triplets were followed up from birth to seven. At four and seven years the psychological status of the mothers and their relationships with the triplets were evaluated using a semi-structured interview and the level of depression was measured using a standardized scale (CES-D). At seven years the scores were compared to those of mothers having a singleton child of the same age. RESULTS: At seven years three mothers of triplets out of 11 still suffered of depressive symptoms. These symptoms were more frequent than among control mothers but non significantly. One mother of triplets out of two (6/11), twice more than at four years, appreciated the increase of her educative tasks and the decrease of practical problems. In the other half of the sample problems still persisted between adults and children. CONCLUSION: Although the situation seemed to improve at seven years, the mother's psychological distress and quality of relationship with the children remained preoccupying in one family out of two.

Depression↗
PubMed2000

Changes in risk factors of preterm delivery in France between 1981 and 1995.

Because of the important changes in medical care and the social context of pregnancy, the relevance of well-established risk factors of preterm delivery (< 37 weeks) needs to be re-assessed. The objective of this study was to determine whether the associations between maternal characteristics and preterm delivery in France in 1995 were similar to those in 1981. We used two national representative samples of births, 5577 newborns in 1981 and 13318 in 1995. Univariable and multivariable analyses were applied to identify variables associated with increased risk of preterm delivery. Some risk factors were similar in 1981 and 1995, including age > 34 years and previous adverse obstetric history. Other factors that were observed in 1981 but which were not linked to preterm delivery in 1995 included the mothers being very young, single or foreign. However, parity and previous induced abortion were associated with preterm delivery in 1995, but not in 1981. These results show that the definition of high-risk groups used in prevention programmes should be brought up to date regularly.

Abortion, Induced↗
PubMed2000

[Risk factors for prematurity in France and comparisons between spontaneous prematurity and induced labor: results from The National Perinatal Survey 1995].

OBJECTIVE: To study risk factors of total preterm delivery, spontaneous preterm delivery and induced preterm delivery. POPULATION: Representative sample of births in 1995 in France, including 12869 single births. METHOD: Preterm deliveries included all births before 37 weeks. Risk factors were analyzed with logistic regression. Factors of spontaneous preterm delivery (after spontaneous onset of labor) and factors of induced preterm delivery (after induction or cesarean section before labor) were compared with polytomous logistic regression. RESULTS: The main risk factors of preterm delivery were history of adverse pregnancy outcome (ORa=4. 5), history of induced abortion (ORa=1.5), 35 year old or more (ORa=1.5) and inadequate antenatal care (ORa=2.1). Other factors such as age under 20 or being single were not significantly linked to preterm delivery. Risk factors differed slightly between spontaneous and induced preterm deliveries. CONCLUSION: The present risk factors do not always correspond with the well-known factors. Thus the assessment of risk factors would be necessary at regular interval. The small differences between the risk factors of spontaneous preterm delivery and induced preterm delivery may be explained by difficulties in defining those two types of preterm delivery or by difficulties in distinguishing specific causes for each of them.

Adult↗
PubMed1999

Birth outcomes of immigrant women in the United States, France, and Belgium.

OBJECTIVES: To compare maternal characteristics and birth outcomes of Mexico-born and native-born mothers in the United States and those of North African mothers living in France and Belgium to French and Belgian nationals. METHODS: We examined information from single live birth certificates for 285,371 Mexico-born and 3,131,632 U.S.-born mothers (including 2,537,264 U.S.-born White mothers) in the United States, 4,623 North African and 103,345 Belgian mothers in Belgium, and a French national random sample consisting of 632 North African and 11,185 French mothers. The outcomes were mean birthweight, low birthweight, and preterm births. Differences between native/nationals and foreign-born mothers in each country were assessed in bivariate and multivariate analyses controlling for maternal risk factors. RESULTS: The adjusted odds for low birthweight were lower for immigrants than native/nationals by 32% in the United States, by 32% in Belgium, and by 30% in France. The adjusted odds for preterm births were lower for immigrants compared with native/nationals by 11% in the United States and by 23% in Belgium. In France, the odds for preterm births were comparable for immigrants and naturalized mothers. Infants of immigrant mothers also had higher mean birthweights in all three countries. CONCLUSION: Despite their disadvantaged status, Mexico-born and North African-born women residing in the United States, France, and Belgium show good birth outcomes. These cannot be explained solely by traditional risk factors. Protective factors and selective migration may offer further clues.

Adolescent↗