A simple model for complex dynamical transitions in epidemics.
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Dramatic changes in patterns of epidemics have been observed throughout this century. For childhood infectious diseases such as measles, the major transitions are between regular cycles and irregular, possibly chaotic epidemics, and from regionally synchronized oscillations to complex, spatially incoherent epidemics. A simple model can explain both kinds of transitions as the consequences of changes in birth and vaccination rates. Measles is a natural ecological system that exhibits different dynamical transitions at different times and places, yet all of these transitions can be predicted as bifurcations of a single nonlinear model. (+info)
Polycystic ovaries and recurrent miscarriage--a reappraisal.
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The prevalence of polycystic ovaries (PCO) was established amongst 2199 consecutive women (median age 33 years; range 19-46) with a history of recurrent miscarriage (median 3; 3-14). A diagnosis of PCO was made if the ovarian volume was enlarged (>9 ml), there were >/=10 cysts of 2-8 mm in diameter in one plane and there was increased density of the stroma. In a cohort study, the prospective pregnancy outcome of 486 of the women scanned who were antiphospholipid antibody negative and who received no pharmacological treatment during their next pregnancy was studied. The prevalence of PCO was 40.7% (895/2199). The livebirth rate was similar amongst women with PCO (60.9%; 142/233) compared to that amongst women with normal ovarian morphology (58.5%; 148/253; not significant). Neither an elevated serum luteinizing hormone concentration (>10 IU/l) nor an elevated serum testosterone concentration (>3 nmol/l) was associated with an increased miscarriage rate. Polycystic ovarian morphology is not predictive of pregnancy loss amongst ovulatory women with recurrent miscarriage conceiving spontaneously. The search for a specific endocrine abnormality that can divide women with PCO into those with a good and those with a poorer prognosis for a future successful pregnancy continues. (+info)
Reproductive longevity and increased life expectancy.
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BACKGROUND: Female life expectancy in developed countries has increased by 30 years in the twentieth century. AIM: To determine if there has been an increase in reproductive longevity. METHODS: We analysed age-specific fertility data from birth statistics for the USA, Canada, Japan, France, Sweden, the UK and Australia. RESULTS: Since 1940, birth rates for women aged 35 and over have declined. Among women aged 50 years and older, there has been no increase in births. Fertility rates in 1990 were 0.0 to 0.044 per 1000 women, with total numbers ranging from 0 to 60 births. CONCLUSION: The fertile years have not been prolonged in the cohort of women whose life expectancy has increased so dramatically this century. This suggests that reproductive senescence is tightly controlled and not extended by factors that enhance female longevity. Other physiological mechanisms may also be fixed within narrow age limits. (+info)
Economic activity and congenital anomalies: an ecologic study in Argentina. ECLAMC ECOTERAT Group.
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In this study, we analyze the association between industrial activity and the occurrence of 34 congenital anomalies. We selected 21 counties in Argentina during 1982-1994 and examined a total of 614,796 births in these counties in consecutive series. We used the International Standard Industrial Classification of All Economic Activities (United Nations, 1968) as an indicator of exposure to 80 specific industrial activities. Incidence rate ratios for each congenital anomaly were adjusted by the socioeconomic level of the county according to a census index of social deprivation. For a given exposure/anomaly association to be considered as significant and relevant, the exposure had to be a statistically significant risk for the occurrence of the anomaly and an increase in the birth prevalence rate of the congenital anomaly type involved had to be observed in those counties where the putative causal activity was being performed. Significant associations (p < 0.01) were identified between textile industry and anencephaly, and between the manufacture of engines and turbines and microcephaly. These observations are consistent with previous reports on occupational exposure, and their further investigation by means of case-control studies is recommended. (+info)
Adolescent pregnancy and childbearing: levels and trends in developed countries.
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CONTEXT: Adolescent pregnancy occurs in all societies, but the level of teenage pregnancy and childbearing varies from country to country. A cross-country analysis of birth and abortion measures is valuable for understanding trends, for identifying countries that are exceptional and for seeing where further in-depth studies are needed to understand observed patterns. METHODS: Birth, abortion and population data were obtained from various sources, such as national vital statistics reports, official statistics, published national and international sources, and government statistical offices. Trend data on adolescent birthrates were compiled for 46 countries over the period 1970-1995. Abortion rates for a recent year were available for 33 of the 46 countries, and data on trends in abortion rates could be gathered for 25 of the 46 countries. RESULTS: The level of adolescent pregnancy varies by a factor of almost 10 across the developed countries, from a very low rate in the Netherlands (12 pregnancies per 1,000 adolescents per year) to an extremely high rate in the Russian Federation (more than 100 per 1,000). Japan and most western European countries have very low or low pregnancy rates (under 40 per 1,000); moderate rates (40-69 per 1,000) occur in Australia, Canada, New Zealand and a number of European countries. A group of five countries--Belarus, Bulgaria, Romania, the Russian Federation and the United States--have pregnancy rates of 70 or more per 1,000. The adolescent birthrate has declined in the majority of industrialized countries over the past 25 years, and in some cases has been more than halved. Similarly, pregnancy rates in 12 of the 18 countries with accurate abortion reporting showed declines. Decreases in the adolescent abortion rate, however, were less prevalent. CONCLUSIONS: The trend toward lower adolescent birthrates and pregnancy rates over the past 25 years is widespread and is occurring across the industrialized world, suggesting that the reasons for this general trend are broader than factors limited to any one country: increased importance of education, increased motivation of young people to achieve higher levels of education and training, and greater centrality of goals other than motherhood and family formation for young women. (+info)
Historical analysis of the development of health care facilities in Kerala State, India.
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Kerala's development experience has been distinguished by the primacy of the social sectors. Traditionally, education and health accounted for the greatest shares of the state government's expenditure. Health sector spending continued to grow even after 1980 when generally the fiscal deficit in the state budget was growing and government was looking for ways to control expenditure. But growth in the number of beds and institutions in the public sector had slowed down by the mid-1980s. From 1986-1996, growth in the private sector surpassed that in the public sector by a wide margin. Public sector spending reveals that in recent years, expansion has been limited to revenue expenditure rather than capital, and salaries at the cost of supplies. Many developments outside health, such as growing literacy, increasing household incomes and population ageing (leading to increased numbers of people with chronic afflictions), probably fueled the demand for health care already created by the increased access to health facilities. Since the government institutions could not grow in number and quality at a rate that would have satisfied this demand, health sector development in Kerala after the mid-1980s has been dominated by the private sector. Expansion in private facilities in health has been closely linked to developments in the government health sector. Public institutions play by far the dominant role in training personnel. They have also sensitized people to the need for timely health interventions and thus helped to create demand. At this point in time, the government must take the lead in quality maintenance and setting of standards. Current legislation, which has brought government health institutions under local government control, can perhaps facilitate this change by helping to improve standards in public institutions. (+info)
Births: final data for 1998.
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OBJECTIVES: This report presents 1998 data on U.S. births according to a wide variety of characteristics. Data are presented for maternal demographic characteristics including age, live-birth order, race, Hispanic origin, marital status, and educational attainment; maternal lifestyle and health characteristics (medical risk factors, weight gain, and tobacco and alcohol use); medical care utilization by pregnant women (prenatal care, obstetric procedures, complications of labor and/or delivery, attendant at birth, and method of delivery); and infant health characteristics (period of gestation, birthweight, Apgar score, abnormal conditions, congenital anomalies, and multiple births). Also presented are birth and fertility rates by age, live-birth order, race, Hispanic origin, and marital status. Selected data by mother's State of residence are shown including teenage birth rates and total fertility rates, as well as data on month and day of birth, sex ratio, and age of father. Trends in fertility patterns and maternal and infant characteristics are described and interpreted. METHODS: Descriptive tabulations of data reported on the birth certificates of the 3.94 million births that occurred in 1998 are presented. RESULTS: Birth and fertility rates increased in 1998 by about 1 percent, the first increase since 1990. Birth rates for teenagers fell 2-5 percent. Rates for women in their twenties increased 1-2 percent each, whereas rates for women in their thirties rose 2-4 percent. All measures of childbearing by unmarried women increased in 1998; the number of births rose 3 percent, the birth rate increased about 1 percent while the percent of births that were to unmarried women rose to 32.8 percent. Smoking by pregnant women overall dropped again in 1998, but continued to increase among teenagers. Improvements in prenatal care utilization continued. The cesarean delivery rate increased for the second year after declining for 7 consecutive years. The proportion of multiple births continued to rise; higher order multiple births (e.g., triplets, quadruplets) rose by 13 percent in 1998, following a 14 percent rise from 1996 to 1997. Key measures of birth outcome--the percents of low birthweight and preterm births--increased. These changes are in large part the result of increases in multiple births. (+info)
Fertility outcome after ectopic pregnancy and use of an intrauterine device at the time of the index ectopic pregnancy.
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Fertility after ectopic pregnancy (EP) was investigated in a non-selected population taking into account intrauterine device (IUD) use at the time of the EP. Between January 1992 and June 1996, 647 women listed in the EP register of Auvergne (France) were followed up. The analysis included only the 328 women who were seeking to become pregnant: 23 women using IUD at the time of the index EP (IUD users) and 305 IUD non-users. Among IUD users, there was no recurrence of EP, and the 1 year cumulative rate was 87% [95% confidence interval (CI): 73-100%] for intrauterine pregnancies and 86% (95% CI: 72-100%) for deliveries. Among IUD non-users, the 2 year cumulative rate for recurrence of EP was 28% (95% CI: 17-39%), and the 1 year cumulative rates were 60% (95% CI: 53-66%) for intrauterine pregnancies and 44% (95% CI: 38-56%) for deliveries. The adjusted intrauterine pregnancy rate of IUD users was not significantly different from that of IUD non-users. However, IUD non-users had more miscarriages, so their delivery rate was lower. (+info)