Allergy and acute leukaemia in children with Down syndrome: a population study. Report from the Mexican inter-institutional group for the identification of the causes of childhood leukaemia.

BACKGROUND: Allergies have been described as protective factors against the development of childhood acute leukaemia (AL). Our objective was to investigate the associations between allergy history and the development of AL and acute lymphoblastic leukaemia (ALL) in children with Down syndrome (DS). METHODS: A case-control study was performed in Mexico City. The cases (n=97) were diagnosed at nine public hospitals, and the controls (n=222) were recruited at institutions for children with DS. Odds ratios (OR) were calculated. RESULTS: Asthma was positively associated with AL development (OR=4.18; 95% confidence interval (CI): 1.47-11.87), whereas skin allergies were negatively associated (OR=0.42; 95% CI: 0.20-0.91). CONCLUSION: Our findings suggest that allergies and AL in children with DS share biological and immune mechanisms. To our knowledge, this is the first study reporting associations between allergies and AL in children with DS.

Breastfeeding and early infection in the aetiology of childhood leukaemia in Down syndrome.

BACKGROUND: For a child to develop acute leukaemia (AL), environmental exposure may not be sufficient: interaction with a susceptibility factor to the disease, such as Down syndrome (DS), may also be necessary. We assessed whether breastfeeding and early infection were associated with the risk of developing AL in children with DS. METHODS: Children with DS in Mexico City, and either with or without AL, were the cases (N=57) and controls (N=218), respectively. Population was divided in children with AL and with acute lymphoblastic leukaemia (ALL) and also in children < or = 6 and >6 years old. RESULTS: Breastfeeding and early infections showed moderate (but not significant) association for AL, whereas hospitalisation by infection during the first year of life increased the risk: odds ratios (confidence interval 95%) were 0.84 (0.43-1.61), 1.70 (0.82-3.52); and 3.57 (1.59-8.05), respectively. A similar result was obtained when only ALL was analysed. CONCLUSION: We found that breastfeeding was a protective factor for developing AL and ALL, and during the first year of life, infections requiring hospitalisation were related to a risk for developing the disease in those children with DS >6 years of age. These data do not support the Greaves's hypothesis of early infection being protective for developing ALL.

Incidence of childhood cancer in Latin America and the Caribbean: coverage, patterns, and time trends / Incidencia del cáncer infantil en América Latina y el Caribe: cobertura de los registros, patrones y tendencias a lo largo del tiempo / Incidência de câncer infantil na América Latina e no Caribe: cobertura, padrões e tendências temporais

ABSTRACT Objective. To provide a comprehensive overview of geographical patterns (2001-2010) and time trends (1993-2012) of cancer incidence in children aged 0-19 years in Latin America and the Caribbean (LAC) and interpret the findings in the context of global patterns. Methods. Geographical variations in 2001-2010 and incidence trends over 1993-2012 in the population of LAC younger than 20 years were described using the database of the third volume of the International Incidence of Childhood Cancer study containing comparable data. Age-specific incidence per million person-years (ASR) was calculated for population subgroups and age-standardized (WSR) using the world standard population. Results. Overall, 36 744 unique cases were included in this study. In 2001-2010 the overall WSR in age 0-14 years was 132.6. The most frequent were leukemia (WSR 48.7), central nervous system neoplasms (WSR 23.0), and lymphoma (WSR 16.6). The overall ASR in age group 15-19 years was 152.3 with lymphoma ranking first (ASR 30.2). Incidence was higher in males than in females, and higher in South America than in Central America and the Caribbean. Compared with global data LAC incidence was lower overall, except for leukemia and lymphoma at age 0-14 years and the other and unspecified tumors at any age. Overall incidence at age 0-19 years increased by 1.0% per year (95% CI [0.6, 1.3]) over 1993-2012. The included registries covered 16% of population aged 0-14 years and 10% of population aged 15-19 years. Conclusions. The observed patterns provide a baseline to assess the status and evolution of childhood cancer occurrence in the region. Extended and sustained support of cancer registration is required to improve representativeness and timeliness of data for childhood cancer control in LAC.

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RESUMO Objetivo. Apresentar uma visão abrangente dos padrões geográficos (2001 a 2010) e das tendências temporais (1993 a 2012) da incidência de câncer em crianças e jovens de 0 a 19 anos na América Latina e no Caribe (ALC) e interpretar os resultados no contexto de padrões mundiais. Métodos. Foram descritas variações geográficas de 2001 a 2010 e tendências de incidência de 1993 a 2012 na população com menos de 20 anos da ALC usando informações comparáveis da base de dados do terceiro volume do estudo International Incidence of Childhood Cancer. Foram calculadas taxas de incidência específica por idade por milhão de pessoas-ano (ASR, na sigla em inglês) para subgrupos populacionais e taxas padronizadas por idade usando a população padrão mundial (WSR, na sigla em inglês). Resultados. No total, foram incluídos 36 744 casos únicos. No período de 2001 a 2010, a WSR para todos os tumores combinados na faixa etária de 0 a 14 anos foi de 132,6. Os diagnósticos mais frequentes foram leucemia (WSR de 48,7), neoplasias do sistema nervoso central (WSR de 23,0) e linfoma (WSR de 16,6). A ASR para todos os tumores combinados na faixa etária de 15 a 19 anos foi de 152,3, e a maior taxa foi a de linfoma (ASR de 30,2). A incidência foi maior no sexo masculino do que no sexo feminino e maior na América do Sul do que na América Central e no Caribe. De modo geral, em comparação com as estimativas mundiais, a incidência na ALC foi menor, exceto para leucemia e linfoma entre 0 e 14 anos e para outros tumores e tumores não especificados em qualquer idade. A taxa de incidência na faixa etária de 0 a 19 anos aumentou em 1,0% ao ano (IC de 95% [0,6, 1,3]) entre 1993 e 2012. Os registros incluídos cobriam 16% da população de 0 a 14 anos e 10% da população de 15 a 19 anos. Conclusões. Os padrões observados servem de referência para avaliar o status e a evolução da ocorrência de câncer infantil na região. É necessário garantir um apoio ampliado e consistente aos registros de câncer para aprimorar a representatividade e a disponibilidade das informações em tempo adequado para o controle do câncer infantil na ALC.

Epidemiology of cancer in children under one year of age in Mexico City.

In this work, the epidemiology of cancer in children under one year of age in Mexico City is described. A survey (observational, descriptive and prolective study) from 1 January 1996 to 31 December 1999 was conducted at two paediatric hospitals of the Instituto Mexicano de Seguro Social in Mexico City (IMSS-MC). To calculate both the general and the by sex incidence (rates are given per 10) all new cases recorded for children under one year of age (numerator) and Mexico City population served by the IMSS (denominator) were used. When the total of 34 cases that fulfilled the requirements was analysed, an incidence of 194.5 was obtained. Leukaemia occupied first place with a rate of 68.6 and hepatic and germinal cells tumours occupied second place with an incidence of 28.6, whereas peripheral nervous system tumours (neuroblastoma) showed a very low rate (11.4). Overall, the male/female ratio for tumours was 1.4:1, with the ratio varying with different types of tumours. Cancer incidence in this population was shown to be close to that in developed countries, but differed in the distribution of the type of tumour: leukaemia had a very high incidence and that for neuroblastoma was very low.

The prevalence of NIDDM and associated coronary risk factors in Mexico City.

OBJECTIVE: To determine the prevalence of diabetes and associated coronary risk factors in the Mexico City population. RESEARCH DESIGN AND METHODS: A sample of 805 adults was selected from Mexico City. The participants, 20-90 years of age and living in the city, were selected by the method of multistage cluster sampling with proportional allocation. Diabetes was diagnosed by previous history or if fasting blood glucose was > or = 7.8 mmol/l ( > or = 7.8 mmol/l ( > or = 140 mg/dl). RESULTS: The crude rate prevalence of NIDDM was 8.7%, with an age-adjusted rate of 10.6% for women and 6.0% for men. Age strongly influenced diabetes prevalence, with a chi 2 of risk tendency of 39.1 (P < 0.00005). A significant proportion (5.9%) of younger individuals (35-44 years of age) was affected by the disease. Diabetes was associated with advanced age, had a greater impact in the low-income group, and showed increased odds ratio for hypertension, dyslipidemias, and myocardial infarction in men and women and for obesity only in women. CONCLUSION: There is a high prevalence of NIDDM in Mexico City that also strikes a significant group of younger individuals. Associated coronary risk factors are also common and more prevalent in diabetic individuals. Current epidemiological data in Mexico and Mexican-Americans in the U.S. suggest that we may be on the ascending limb for diabetes and cardiovascular disease. There is a critical need for resources to be allocated to programs for primary and secondary prevention, which must be well structured and organized so that proper standards of care are followed to prevent progression of the disease.

Univariate and multivariate analysis of risk factors for ovarian cancer: case-control study, Mexico City.

Female residents of the southern part of Mexico City diagnosed with epithelial ovarian cancer between 1989 and 1992 (n = 172) were interviewed regarding reproductive events. The same information was obtained from the controls (n = 441). There was an elevated risk for ovarian cancer associated with an increased number of abortions, relative risk = 3.66 (95% confidence interval = 1.02 - 13.45) for women with four fetal losses. Ovarian cancer risk was shown to decrease as parity increased, reaching a relative risk of 0.23 (95% confidence interval = 0.09 - 0.55) in women with four or more live births in the postmenopausal group. This negative association seems less evident in overall cases. Logistic regression methods were used and abortions and high estimated number of ovulatory cycles were found to be associated with an increased risk of ovarian cancer. The inclusion of nonreproductive variables such as educational status, in the logistic model, showed that cases had a lower educational level than that of controls.

High blood pressure and cardiovascular risk factors in an adult population of Mexico City. Characteristics of the studied population.

The present report is a description of the characteristics of a studied population and of the methodology used in a study performed to investigate high blood pressure prevalence and cardiovascular risk factors among the adult population of Mexico City. A cross-sectional study was conducted from January 1991 to March 1992. Random samplings of multiple stages was used and 825 adult subjects were studied in Mexico City. The following measurements were registered: blood pressure, body mass index (BMI), waist-hip ratio (WHR), total cholesterol (TC), triglycerides (TG), high density lipoproteins (HDL-C) and low density lipoproteins (LDL-C), lipoprotein (a) (Lp(a)), glucose and insulin. Personal and family history of cardiovascular illness were investigated, as well as exposure to some risk factors such as smoking, alcohol consumption and sedentarism. The response rate was 86.6%. The prevalence of high blood pressure was 21.1%, and of non-insulin dependent diabetes mellitus was 8.7%. Frequency of dyslipidemia in the studied sample was 24.4% for high TG, 23.6% for low HDL-C, 23.6% for high LDL-C, 14.9% for Lp(a) excess (Lp(a) > or = 30 mg/dl; overweight and obesity were more prevalent among women. The diversity of living conditions among the population of Mexico City was included in the sampling strategy design, not only to register the high blood pressure (HBP) frequency in each stratum but to identify other cardiovascular risk factors which could be decisive in the development of HBP. Regarding the features of the studied population, BMI did not reveal differences among men, but their TG levels were higher and HDL levels lower than those of other populations. In women, the results obtained for BMI, WHR, lipids and lipoproteins were also higher compared with the mean reported for other populations.

Incidence trends of acute leukemia among the children of Mexico City: 1982-1991.

The objective of this study was to identify the tendency of acute leukemia among children in Mexico City from 1982 to 1991. A hospital survey was performed. Medical records of children under 15 years of age with a diagnosis of acute leukemia were reviewed. The cases were chosen from hospitals which provide medical attention to children with cancer in Mexico City. The annual incidence rate (AIR) was calculated in general, by sex, age groups (under 1 year of age, from 1 to 4 years, 5 to 9 years and 10 to 14 years) and standardized with the world population. The trend was evaluated with Spearman's correlation method. Acute lymphoblastic leukemia showed a significantly increasing trend during the study period. The AIR was 7.75 (per million) in 1982 and 22.19 (per million) in 1991. For age groups a tendency to increase was observed in females of age group 1 to 4 years and in males of age group 10 to 14 years. Acute non-lymphoblastic leukemia did not display a specific trend. In conclusion, acute lymphoblastic leukemia shows a tendency to increase in the children of Mexico City.

Nutritional state alterations in children with acute lymphoblastic leukemia during induction and consolidation of chemotherapy.

The objective of the study was to determine if children with high risk acute lymphoblastic leukemia (ALL) exhibit higher frequency of alterations in nutritional state during the phases of induction and consolidation of chemotherapy than children with low risk ALL, based on the arm muscle area. The design was concurrent comparative cohorts. It was performed at pediatric hematology service of the Hospital General del Centro Médico Nacional "La Raza" and hematology service of the Hospital de Pediatría del Centro Médico Nacional "Siglo XXI". One hundred-five patients were incorporated into the study: 53 with high risk (HR) ALL and 52 with low risk (LR) ALL. Basal measurements of arm circumference and tricipital skinfold were surveyed monthly (for 3 months) by standardized personnel. Altered nutritional state during follow-up was defined as the loss of 10% or more of the arm muscular area (AMA) measured at diagnosis. Statistics of proportion analysis with a significance level of 0.05 and relative risk (RR) with confidence intervals (CI) were calculated. In the first month the RR was 0.77 (CI 0.31-1.87); the LR group was the most affected. In the second month the RR was 7.31 (CI 1.41-38.03); the most affected group was the HR. In the third month the RR was 1.77 (CI 0.60-4.92); the HR group was the most affected. High-risk patients show a higher frequency of nutritional state alterations reflected in AMA during the second month after diagnosis. This may be caused by the more aggressive chemotherapy received by these patients.

Epidemiology of lymphomas in children residing in Mexico City.

BACKGROUND: The aim of this paper is to present the epidemiological characteristics of time, subject and place of lymphomas in children residing in Mexico City, Mexico (MC). METHODS: The type of study was a retrospective hospital survey. All records of children with lymphomas registered between 1982 and 1991 at the main hospitals that treat children with cancer in MC were reviewed. Neoplasms were classified into Hodgkin's disease (HD) and non-Hodgkin's lymphomas (NonHL). Trend and incidence by sex, age and area of residence in MC were evaluated. Time of diagnosis, as well as parental occupation and educational level, were registered. RESULTS: A trend was only observed for HD in the total group (r:0.62; P = 0.05). In 1991, incidence for HD was 6.12 (rates x 10(6)) and 3.87 for NonHL. The highest average incidence was found in children 5-9 years of age (5.40) for HD, and in the age groups of 1-4 and 5-9 (3.10 and 3.33, respectively), for NonHL. Incidence was higher among boys for both lymphoma categories, but the male-to-female ratio was much higher in HD. Time of diagnosis, incidence in terms of place of residence, and parental educational level and occupation also differed from one lymphoma category to the other. CONCLUSION: The epidemiology of HD is different from that of NonHL, both showing a pattern similar to that of Latin American children.

Malnutrition in childhood lymphoblastic leukemia: a predictor of early mortality during the induction-to-remission phase of the treatment.

BACKGROUND: Previous reports have shown that undernourished children with acute lymphoblastic leukemia (ALL) have a poorer long-term survival as compared with children with normal nourishment status. It has been shown that both the relapse and mortality rates of undernourished children with ALL are higher during the continuation phase of the chemotherapy and are apparently related to a poor tolerance of ablative chemotherapy. No previous articles have analyzed the early mortality rate of these patients. METHODS: We carried out a case-control study, and have studied the effect of severe malnutrition on the mortality of 17 children with ALL during the initial induction-to-remission phase of the treatment. These 17 cases were compared with 76 controls who had survived at least the phases of induction and consolidation. RESULTS: It was found that the chance of dying during the initial phase of the treatment was 2.6 times higher (confidence interval 95%: 0.55-11.89) in undernourished children with ALL than in those children with normal nourishment status. The risk of death increased with the severity of undernourishment (p = 0.04). CONCLUSIONS: These data confirm the prognostic value of malnutrition in children with ALL and suggest that undernourishment may also influence early mortality during the induction-to-remission phase of the treatment.

Prevalence of high blood pressure and associated coronary risk factors in an adult population of Mexico City.

BACKGROUND: Several studies have addressed arterial hypertension prevalence in Mexico. However, few include an analysis of other types of hypertension and their associated risk factors. The present work describes the prevalence of high blood pressure (HBP), isolated systolic hypertension (ISH) and diastolic hypertension (DH) and their association to certain risk factors of cardiovascular disease in an adult population of Mexico City. METHODS: A cross-sectional study was performed on 825 subjects aged between 20 and 90 years, selected by multistage cluster sampling. HBP was diagnosed by previous history if systolic blood pressure was > or = 140 mmHg and/or diastolic blood pressure > or = 90 mmHg. The measurements taken included body mass index, waist-to-hip ratio, systolic and diastolic blood pressure, levels of insulin, glucose, trigylycerides, total cholesterol, high and low density lipoprotein cholesterol, and lipoprotein(a). RESULTS: Prevalence adjusted by age for HBP was 19.4%, for ISH, 4.7%, and for DH, 4.1%. Age had an important influence on HBP and ISH with a highly significant X2t. The profile of metabolic variables was modified according to sex and type of hypertension. Thus, in DH, metabolic variables were more affected than in other types of hypertension. CONCLUSIONS: Results in HBP prevalence in the present study were lower than in other surveys performed in Mexico. It must be noted, however, that much care should be taken to choose the strategy of subject selection, since results of the prevalence of a disease depend on it to a great extent. The ISH and DH and their association to risk factors must be studied thoroughly because they constitute different clinical entities.

[Frequency and risk factors associated with metronidazole therapeutic noncompliance]. / Frecuencia y factores de riesgo asociados al incumplimiento terapéutico con metronidazol.

OBJECTIVE: to determine the frequency and risk factors of non-compliance to oral metronidazole. STUDY DESIGN: comparative cross-sectional survey. STUDY UNITS: 111 patients who received oral metronidazole. SETTING CHARACTERISTICS: two medical units: one primary level unit and one secondary care unit of the Mexican Institute of Social Security. MEASUREMENTS: non-compliance was assessed by home interview and pill count. MAIN RESULTS: frequency of non-compliance was 55%. Risk factors for non-compliance were: female sex (OR = 3.0; p less than 0.05); side effects (OR = 3.1; p less than 0.05); low literacy (OR = 3.75; p less than 0.05). Stratified analysis showed no interaction between variables. CONCLUSIONS: frequency of non-compliance to metronidazole is high, and could affect the effectiveness of medical care. Female patients with low literacy and who suffer side effects are a high risk group for non-compliance.

[Diagnostic performance of immunologic tests in amebic liver abscess using receiver operating characteristic curves]. / Rendimiento diagnóstico de las pruebas inmunológicas en absceso hepático amibiano a través de curvas de características operantes del receptor.

Objectives. 1) To identify the tests of immunological diagnosis with a high diagnostic efficiency in amebic liver abscess. 2) To determine the ideal cutoff point for such tests. 3) To identify the influence degree of the antigen used over the test efficiency. Design. Comparative survey. Study units. Analysis of 24 articles identified in the medical literature about tests of immunological diagnosis in amebic liver abscess. Measurements. Starting from the articles, operating characteristics curves (ROC) were established derived from the test application to patients with amebic liver abscess. Results. A great variability in the diagnostic efficiency was identified between the various tests, even when the analysis was focused on the investigations of a specific test. It was not possible to conclude which test had a major degree of efficiency due to such variability. The cutoff level considered as relevant was higher than the one traditionally used for indirect hemagglutination and it had concordance with the one presently accepted for the fluorescence antibodies test. By maintaining steady the spectrum of the study patients and the type of test, variability among the tests persisted. This was due to the use of different antigens. Conclusions. A great variation in the diagnostic efficiency of the analyzed tests was identified. The variation source was the type of test, the antigen used and probably the illness spectrum.

[Cryptosporidium parvum infection in malnourished and non malnourished children without diarrhea in a Mexican rural population]. / Infección por Cryptosporidium parvum en niños desnutridos y no desnutridos sin diarrea en una población rural mexicana.

UNLABELLED: Cryptosporidium parvum is associated with diarrheic disease and mainly affects children and immunocompromised hosts. In most of the cases, cryptosporidiosis infection is asymptomatic in immunocompetent subjects. The objectives of the study were to determine the frequency of asymptomatic infection caused by the parasite in children with and without malnutrition and to determine the risk factors associated to infection. METHODS: Children from one to fifteen years old without diarrhea were included, somatometry were performed. The socioeconomic and sanitary conditions were investigated for each family and community. The Faust method and Kinyoun stain were employed identify parasites and Cryptosporidium parvum in feces. Odds ratio (OR), 95% confidence intervals (75% CI), chi 2 Mantel-Haenszel, Fisher exact test and chi 2 trends were calculated. RESULTS: One hundred thirty two children were included. In 10/132 (7.5%) cysts of Cryptosporidium were found, 7/71 in children with malnutrition (9.8%) and 3/61 without malnutrition (4.9%) p = 0.23. 69.7% of the children had parasitosis. According to the presence of C. parvum in feces, the different factors calculated were: Diarrhea in family OR = 5.82 (95%IC 0.86-39.18), not hand washing OR = 5.08 (95%IC 0.62-110.49), age less than 5 years old OR = 4.90 (95%IC 0.60-106.9), drinking non-potable water OR = 3.34 (95%IC 0.40-73.01) and malnutrition 2.11 (95%IC 0.46-10.89). Association was found between the number of people in the same house and the risk of infection (p = 0.005). The presence of diarrhea in the family (OR = 4.15, 95%IC 0.47-36.91) and drinking non-potable water (OR = 4.19, 95%IC 0.48-36.32) were the significant factors in the regression logistic model. CONCLUSIONS: The frequency of Cryptosporidium infection were 7.5%. Diarrhea in the family, overcrowding and drinking non-potable water were associated with C. parvum infection, malnutrition was not a significant risk factor.

Validation of a prognostic index in the critically ill newborn.

OBJECTIVE: Elaborate and assess the degree of validity of a prognostic model for evaluating patients admitted to the Neonatal Intensive Care Unit (NICU). DESIGN: Cases and controls nested in a cohort. SETTING: NICU of two tertiary hospitals and another second level hospital. PATIENTS: The study was carried out in two phases. During the first phase (elaboration of a model), 336 newborns were studied; 112 belonged to the case group (dead patients) and 224 to the control group (live patients discharged). For the second phase (model validation), 300 patients were included that did not participate in the first phase, 100 cases and 200 controls. MEASUREMENTS: For each patient admitted to the study, clinical, paraclinical, perinatal and comorbidity factors were determined within the first 12 hours. Variables of statistical significance in the bivariate analysis were included in a logistic regression model with the objective of identifying a prognostic model. RESULTS: The variables that constituted the prognostic index were gestational age x birth weight, the paO2/FiO2 ratio x O2 saturation, arrest cardiac, major congenital malformations, septicemia and base excess. The model showed to have a sensitivity of 70% and a specificity of 91% during the elaboration cohort. In the validation cohort, sensitivity was 68% and specificity was 92%, a positive predictive value of 80%, negative predictive value of 85% and a correct classification rate was 84%. CONCLUSIONS: The Neonatal Mortality Prognostic Index (NMPI) developed in this study showed to be useful for the evaluation of hospital mortality for severely ill newborns admitted to NICU.

[Classification by levels of clinico-epidemiological research designs]. / Clasificación en niveles de los diseños de investigación clínico-epidemiológicos.

The objective was to identify the characteristics of epidemiologic designs enabling their classification. A critical review of the literature in the clinical epidemiologic area was done to establish the main differences between designs. A meeting with experts to discuss this controversial topic and obtain criteria by consensus was organized. We propose an integral classification based on levels with two fundamental shafts: intervention and explanatory reasoning.

[Puerperium with short-term hospitalization]. / Puerperio de corta estancia hospitalaria.

Seventy seven cases with discharge before 12 hours post-partum and 240 cases with discharge after 24 or more hours after delivery, were evaluated at Hospital General de México, in an observational, prospective, cohort, study in low risk deliveries. Both groups were reviewed ten days after delivery. There were no different ratios for abnormal uterine hemorrhage, urinary tract infection or endometritis. Thrombophlebitis was more frequent in early discharge patients, both statistically and clinically significant (RR3.58, CI95% 1.48-8.67, P = 0.003). This finding is discussed, as well as measures to prevent it. It is concluded that early discharge programs in low risk conditions, are convenient.

[The trend in pregnancies terminated by a cesarean operation in Mexico during 1991-1995]. / Tendencia de los embarazos terminados por operación cesárea en México durante el periodo 1991-1995.

In the last decades has been a worldwide trend to increase the number of cesarean sections as an alternative of obstetric resolution, phenomenon for which it was proposed a variety of explanation, this fact remains practically unknown in the institutions of the National Health System (NHS) in Mexico. To identify the trend of the pregnancy to end for cesarean sections during the years of 1991-1995 in the 32 states of de country, as well as of all the institutions of the National Health System. Descriptive, cross sectional and retrospective. We use the data of the Bureau of Statistics and Informatics of de Health Ministry of each one of the 32 states of the country, of the years 1991 to 1995, and of the number of cesarean sections made in the hospitals of the different institutions of the NHS. We started off with a data-base, to calculate frequency tables, and the specific rate of the cesarean section for each year, for each one of the states and institutions of the NHS. We calculate the secular trends using the annual rates of cesarean section, for each one of the states and institutions of the NHS. We also made bivariate analysis and estimated the odds ratio (OR) and 95% Confidence Interval (95% IC); and the statistic X2 for trend, setting the two tailed statistic significance level of 0.05. During the study period, there was 7,503,817 births in all hospitals of the NHS, of these births 1,929,865 (25.72%) was resolved by cesarean section. For the whole period it there was a clear trend to increment of the cesarean section, the rate for 1991 was 20.44%, and by 1995 was 28.58%, the raise for the period was 39.82%, with values of the OR for trend of 1.56; 95% IC (1.55-1.57). "P" < 0.05. The rate for institutions attending open population had an increment of 35.08% [OR trend 1.45; 95% IC (1.43-1.46), "p" < 0.05], of them the highest rate was for the State System of Health in 1995 with 29.78%, the rates for the remaining institutions varied from 16.57% for the IMSS/SOLIDARIDAD and 21.7% for the Health Ministry, all trends were statistically significant. In relation to the institutes attending closed population the raise was of 53.27% [OR trend 1.82; 95% IC (1.81-1.83), "p" < 0.05], with the highest rate for the National Defense Ministry which had a rate of 51-15%, the rates for the remaining institutions varied from 33.52% for the Mexican Institute of Social Security (IMSS) to 43.89% for the Institute of Safety and Social Services for the State Workers (ISSSTE), with exception of the Management of the Medical Services of the Mexican Oils (PEMEX) and the Marine Ministry (SECMAR), all trends were statistically significant. When the analysis of the cesarean section rates for the 32 states of the Mexican Republic was carried out, we found that in 1995, the national average rate was 28.58%, the lowest rate corresponded to the state of Zacatecas with 19.82% and the highest to the state of Nuevo León with 42.14%. There was a tendency to increment for all states which varied from 23.55% for the state Chiapas and 67.97% for the states of Querétaro, all increments were statistically significant. We conclude, that rates of cesarean section for both, institutions of NHS and states of the Mexican Republic, are of the highest in the world, no matter what big the interinstitutional and interstate variation are. The highest rates occurred in institutions attending closed population, and the states with a higher degree of socioeconomic development.