Seasonality of birth: Two findings from the decennial census

Abstract

Two results on the seasonality of birth phenomenon are derived from tabulations of 1980 census data: first, that the familiar pattern of spring trough and summer peak prevailed in the decades before the establishment of a national birth registration data system; second, that the seasonal pattern is most pronounced for the lower socioeconomic group.     

Seasonal variation in conception and various pregnancy outcomes

Abstract

U.S. vital registration data on live births and data on abortions and ectopic pregnancies from a national hospital discharge survey were used to examine the seasonality of conceptions and the influence the conception pattern has on the monthly incidence of abortions and ectopic pregnancies. We found that in the United States conceptions follow a consistent seasonal pattern with the peak in November and December. However, when the pattern for conceptions is controlled, the monthly variation for abortions and ectopic pregnancies is not significant. Therefore, we find no monthly excess for any of these outcomes of pregnancy over that expected as a consequence of the seasonality of conception. We suggest the monthly variation for the number of each of these pregnancy outcomes will best be explained when the seasonal variation in conceptions is understood.     

Measuring Under-Five Mortality: Validation of New Low-Cost Methods

Background

There has been increasing interest in measuring under-five mortality as a health indicator and as a critical measure of human development. In countries with complete vital registration systems that capture all births and deaths, under-five mortality can be directly calculated. In the absence of a complete vital registration system, however, child mortality must be estimated using surveys that ask women to report the births and deaths of their children. Two survey methods exist for capturing this information: summary birth histories and complete birth histories. A summary birth history requires a minimum of only two questions: how many live births has each mother had and how many of them have survived. Indirect methods are then applied using the information from these two questions and the age of the mother to estimate under-five mortality going back in time prior to the survey. Estimates generated from complete birth histories are viewed as the most accurate when surveys are required to estimate under-five mortality, especially for the most recent time periods. However, it is much more costly and labor intensive to collect these detailed data, especially for the purpose of generating small area estimates. As a result, there is a demand for improvement of the methods employing summary birth history data to produce more accurate as well as subnational estimates of child mortality.

Methods and Findings

We used data from 166 Demographic and Health Surveys (DHS) to develop new empirically based methods of estimating under-five mortality using children ever born and children dead data. We then validated them using both in- and out-of-sample analyses. We developed a range of methods on the basis of three dimensions of the problem: (1) approximating the average length of exposure to mortality from a mother''s set of children using either maternal age or time since first birth; (2) using cohort and period measures of the fraction of children ever born that are dead; and (3) capturing country and regional variation in the age pattern of fertility and mortality. We focused on improving estimates in the most recent time periods prior to a survey where the traditional indirect methods fail. In addition, all of our methods incorporated uncertainty. Validated against under-five estimates generated from complete birth histories, our methods outperformed the standard indirect method by an average of 43.7% (95% confidence interval [CI] 41.2–45.2). In the 5 y prior to the survey, the new methods resulted in a 53.3% (95% CI 51.3–55.2) improvement. To illustrate the value of this method for local area estimation, we applied our new methods to an analysis of summary birth histories in the 1990, 2000, and 2005 Mexican censuses, generating subnational estimates of under-five mortality for each of 233 jurisdictions.

Conclusions

The new methods significantly improve the estimation of under-five mortality using summary birth history data. In areas without vital registration data, summary birth histories can provide accurate estimates of child mortality. Because only two questions are required of a female respondent to generate these data, they can easily be included in existing survey programs as well as routine censuses of the population. With the wider application of these methods to census data, countries now have the means to generate estimates for subnational areas and population subgroups, important for measuring and addressing health inequalities and developing local policy to improve child survival. Please see later in the article for the Editors'' Summary     

The uncounted: Citizenship and exclusion in the Israeli census of 1948

Previous research on official statistics, and the national census, has established the role of these practices in the construction of modern political institutions, particularly the state and citizenship. Studies have described the use of statistics in transforming a territorial population into a citizenry, but have not examined the role of the census in the exclusion that is an essential element in the constitution of citizenship. Based on a case study of the Israeli national census and registration of 1948, we discuss the use of this census to legitimate an ethnic/national exclusion at the heart of Israeli citizenship. It is this task that explains the peculiar features of our case: a census carried out in wartime, under a 7-hour general curfew.     

Epidemiology of congenital malformations in Gorno-Altaisk, Altai Republic, Russia

A retrospective epidemiological study has been performed using the data from healthcare institutions of the city of Gorno-Altaisk, Altai Republic, Russia for the period from 1983 to 2001. Congenital malformations (CMFs) have been studied in newborns, infants that died at ages under one year, and fetuses after 22 weeks of gestation. The most frequent malformations are those of the musculoskeletal and cardiovascular systems and multiple malformations, which account for 37.68, 18.22, and 8.9% of all congenital malformations, respectively. Their frequencies are 7.38, 3.57, and 1.74 per thousand, respectively. The frequency of congenital malformations subject to registration by the national system of CMF monitoring of the Russian Federation (21 malformation forms) is 6.08 per 1000 births and varies from 8.59 to 21.24. The frequency of the Down syndrome is 0.93 per 1000 births; it did not vary significantly during the period studied. The frequency of limb reduction deformities in the urban population of Altai Republic (0.32 per 1000 births) is higher than in other Siberian regions, including the cities of Kyzyl (Tyva Republic) and Tomsk and the Nyurba and Ust-Aldan uluses of Sakha Republic (Yakutia).     

Racial differences in the relationship between infant mortality and socioeconomic status

This study presents an ecological analysis of the relationship between infant mortality and economic status by race in metropolitan Ohio, using census data on mother's residence and economic status determined by the percentage of low-income families living in each area. The analysis updates previous studies as white-non-white comparisons for total infant mortality are examined for the US censuses of 1960, 1970, 1980, 1990 and 2000; and more detailed period- and broad cause-specific rates are presented for 2000. A pronounced inverse association is consistently found between income status and infant mortality for whites, while for non-whites this pattern first emerges in 1979-81, disappears during the 1980s and then returns more strongly during the 1990s. Similarly, the 2000 data reveal a consistent inverse pattern between income status and infant mortality for white and non-white neonatal and postneonatal death rates, as well as exogenous cause-specific death rates. It is concluded that low-income whites and non-whites have infant mortality rates substantially higher than the overall rate for the population. Policy implications are discussed.     

The Seasonality of Human Births, Melatonin and Cloud Cover

Introduction: Although the seasonality of human births has been known for nearly 175 years, it has not been adequately explained. Societal and environmental reasons have often been cited as the reasons for seasonality. Since increased light is known to initiate reproduction in many animals, photoperiod, light intensity and melatonin are likely variables related to this phenomenon. This retrospective study demonstrates a logical connection between these factors and human conceptions. Methodology: Seasonality data were extracted from previous studies. Daily cloud cover amounts were utilized as indices for environmental light intensity. Variables were evaluated by Pearsonian r. Discussion: Results were evaluated and discussed in a series of 11 sub-studies involving environmental light intensity and the seasonality of human births. Conclusion: Human birth seasonality may be primarily influenced by environmental light intensity with photoperiod in a secondary role. This result is supported by significant r-values for US and Europe, a logical link between US, Canadian, Indian, European, and Hong Kong conceptions as well as the concurrent transition of conceptions and cloud cover. Israeli conceptions, however, contradict US and European patterns.     

Congenital developmental defects in the genetic monitoring system. I. The selection of developmental defects subject to dynamic observation

The requirements for selection of congenital malformations in the system of genetic monitoring as models have been studied. Model malformations have been shown to be easily and reliably diagnosed even in infancy. Their rate should be not less than 1:5000 births. The precise knowledge of the genetics of model forms is needed as well. Down's syndrome registration is the most convenient method for evaluation of mutations in a genome. We recommend registration in total all multiple congenital malformations (without Down's syndrome) for estimation of dominant mutability dynamics, as it was shown that more than 11% of all multiple malformations are caused by sporadic dominant mutations.     

The ecology and evolution of reproductive synchrony

The temporal pattern of breeding in populations is often characterized by a pronounced temporal clustering of births, flowering or seed set. It has long been suspected that this phenomenon is not caused by climatic seasonality alone but that reproductive synchrony represents a strategy that individuals adopt to maximize reproductive success. The classical hypotheses predicting an adaptive advantage of reproductive synchrony incorporate both sociobiological and ecological explanations. However, new theoretical and empirical analyses have shown that the predicted advantage of reproductive synchrony depends on the ecological setting in which populations reproduce, and processes earlier thought to be responsible only for synchrony may under some ecological conditions lead to asynchronous reproduction being the best strategy.     

Variations in number of births and perinatal mortality by day of week in England and Wales.

Analysis of the births that occurred in England and Wales during 1970-6 showed that they followed a seven-day cycle, being concentrated from Tuesdays to Fridays and least numerous on Sundays. This pattern became increasingly pronounced during the period examined. Relatively few births occurred on bank holidays, especially Christmas Day and Boxing Day. In general perinatal mortality was higher among babies born at weekends than among those born on weekdays. It is likely that the pattern seen in the numbers of births is associated to a large extent with elective intervention. It is not possible to draw any conclusions about the pattern seen in perinatal mortality as so far the analysis has been confined to crude rates.     

Deformed nasal septa and relaxed selection

Abstract

Demographic studies undertaken in several Andean countries have found that women residing at high altitudes have significantly fewer live births than do their low altitude counterparts. This reduction has been explained as being due to various factors: the debilitating effects of hypoxia upon the reproductive system; the effects of sociocultural factors which vary with altitude and which affect reproductive behavior; and errors in data collection. In order to examine the validity of some of these hypotheses, the fertility of a group of 906 Bolivian women residing at low, medium, and high altitudes was examined. The women were selected from the lower socioeconomic strata and reported never having used any method of contraception. A detailed analysis of the fertility of these women showed no significant altitude‐related differences in the number of live births. However, as a result of significantly higher childhood mortality rates at altitude, there was a significant reduction in numbers of living children. The results of this study suggest that the collection and analysis of census data that ignores socioeconomic differences within a population or differences among census units in neonatal or early childhood mortality may bias or complicate the study of the impact of altitude on human fertility. Although the present research does not prove that hypoxic stress does not affect the reproductive system, the results suggest that if altitude does reduce fecundity, the reduction is not great and is likely to be shown only through studies of reproductive physiology.     

Can Community Health Workers Report Accurately on Births and Deaths? Results of Field Assessments in Ethiopia,Malawi and Mali

Introduction

Most low-income countries lack complete and accurate vital registration systems. As a result, measures of under-five mortality rates rely mostly on household surveys. In collaboration with partners in Ethiopia, Ghana, Malawi, and Mali, we assessed the completeness and accuracy of reporting of births and deaths by community-based health workers, and the accuracy of annualized under-five mortality rate estimates derived from these data. Here we report on results from Ethiopia, Malawi and Mali.

Method

In all three countries, community health workers (CHWs) were trained, equipped and supported to report pregnancies, births and deaths within defined geographic areas over a period of at least fifteen months. In-country institutions collected these data every month. At each study site, we administered a full birth history (FBH) or full pregnancy history (FPH), to women of reproductive age via a census of households in Mali and via household surveys in Ethiopia and Malawi. Using these FBHs/FPHs as a validation data source, we assessed the completeness of the counts of births and deaths and the accuracy of under-five, infant, and neonatal mortality rates from the community-based method against the retrospective FBH/FPH for rolling twelve-month periods. For each method we calculated total cost, average annual cost per 1,000 population, and average cost per vital event reported.

Results

On average, CHWs submitted monthly vital event reports for over 95 percent of catchment areas in Ethiopia and Malawi, and for 100 percent of catchment areas in Mali. The completeness of vital events reporting by CHWs varied: we estimated that 30%-90% of annualized expected births (i.e. the number of births estimated using a FPH) were documented by CHWs and 22%-91% of annualized expected under-five deaths were documented by CHWs. Resulting annualized under-five mortality rates based on the CHW vital events reporting were, on average, under-estimated by 28% in Ethiopia, 32% in Malawi, and 9% in Mali relative to comparable FPHs. Costs per vital event reported ranged from $21 in Malawi to $149 in Mali.

Discussion

Our findings in Mali suggest that CHWs can collect complete and high-quality vital events data useful for monitoring annual changes in under-five mortality rates. Both the supervision of CHWs in Mali and the rigor of the associated field-based data quality checks were of a high standard, and the size of the pilot area in Mali was small (comprising of approximately 53,205 residents in 4,200 households). Hence, there are remaining questions about whether this level of vital events reporting completeness and data quality could be maintained if the approach was implemented at scale. Our experience in Malawi and Ethiopia suggests that, in some settings, establishing and maintaining the completeness and quality of vital events reporting by CHWs over time is challenging. In this sense, our evaluation in Mali falls closer to that of an efficacy study, whereas our evaluations in Ethiopia and Malawi are more akin to an effectiveness study. Our overall findings suggest that no one-size-fits-all approach will be successful in guaranteeing complete and accurate reporting of vital events by CHWs.     

Note on the reliability and validity of mothers' retrospective reports of their children's birthweights.

Using data from the 1973, 1976, and 1982 National Survey of Family Growth Studies, mothers' retrospective reports of their children's birthweights are compared across surveys and with vital registration data. Comparisons focus on estimated levels for blacks and whites, and on the effects of possible determinants. Despite the fact that nonresponse is more common for blacks, especially for births occurring at dates more distant from the surveys, results show that retrospective reports of low birthweight (less than 5.5 pounds) provide valid and reliable estimates of trends and differentials.     

Epidemiology of Congenital Malformations in Gorno-Altaisk,Altai Republic,Russia

A retrospective epidemiological study has been performed using the data from healthcare institutions of the city of Gorno-Altaisk, Altai Republic, Russia for the period from 1983 to 2001. Congenital malformations (CMFs) have been studied in newborns, infants that died at ages under one year, and fetuses after 22 weeks of gestation. The most frequent malformations are those of the musculoskeletal and cardiovascular systems and multiple malformations, which account for 37.68, 18.22, and 8.9% of all congenital malformations, respectively. Their frequencies are 7.38, 3.57, and 1.74, respectively. The frequency of congenital malformations subject to registration by the national system of CMF monitoring of the Russian Federation (21 malformation forms) is 6.08 per 1000 births and varies from 8.59 to 21.24. The frequency of the Down syndrome is 0.93 per 1000 births; it did not vary significantly during the period studied. The frequency of limb reduction deformities in the urban population of Altai Republic (0.32 per 1000 births) is higher than in other Siberian regions, including the cities of Kyzyl (Tyva Republic) and Tomsk and the Nyurba and Ust-Aldan uluses of Sakha Republic (Yakutia)     

Unwanted conceptions: Research on undesirable consequences

Attempts have been made to identify factors influencing the number of males per 100 females at birth, also called the secondary sex ratio. It has been proposed to vary inversely with the frequency of prenatal losses, but available data lend at best only weak support for this hypothesis. Statistical analyses have shown that comparisons between secondary sex ratios demand large data sets. Variations in the secondary sex ratio that have been reliably identified in family data have mostly been slight and without a notable influence on national birth registers. For Sweden, 1751–1950, the secondary sex ratio among all births and live births revealed increasing trends. The Swedish results are compared with available findings for live births in Finland, Norway, Denmark, and the small Icelandic population. For Norway and Denmark, the secondary sex ratio increased during 1801–1950. A similar, but stronger pattern was observed for Finland (1751–1950) and Iceland (1838–1950). During the latter half of the twentieth century, marked decreases were observed in all countries. Attempts to identify reliable associations between secondary sex ratios and stillbirth rates have been made, but no consistent results have emerged.     

Temporal trends in the secondary sex ratio in Nordic countries

Attempts have been made to identify factors influencing the number of males per 100 females at birth, also called the secondary sex ratio. It has been proposed to vary inversely with the frequency of prenatal losses, but available data lend at best only weak support for this hypothesis. Statistical analyses have shown that comparisons between secondary sex ratios demand large data sets. Variations in the secondary sex ratio that have been reliably identified in family data have mostly been slight and without a notable influence on national birth registers. For Sweden, 1751-1950, the secondary sex ratio among all births and live births revealed increasing trends. The Swedish results are compared with available findings for live births in Finland, Norway, Denmark, and the small Icelandic population. For Norway and Denmark, the secondary sex ratio increased during 1801-1950. A similar, but stronger pattern was observed for Finland (1751-1950) and Iceland (1838-1950). During the latter half of the twentieth century, marked decreases were observed in all countries. Attempts to identify reliable associations between secondary sex ratios and stillbirth rates have been made, but no consistent results have emerged.     

Using Health Extension Workers for Monitoring Child Mortality in Real-Time: Validation against Household Survey Data in Rural Ethiopia

Background

Ethiopia has scaled up its community-based programs over the past decade by training and deploying health extension workers (HEWs) in rural communities throughout the country. Consequently, child mortality has declined substantially, placing Ethiopia among the few countries that have achieved the United Nations’ fourth Millennium Development Goal. As Ethiopia continues its efforts, results must be assessed regularly to provide timely feedback for improvement and to generate further support for programs. More specifically the expansion of HEWs at the community level provides a unique opportunity to build a system for real-time monitoring of births and deaths, linked to a civil registration and vital statistics system that Ethiopia is also developing. We tested the accuracy and completeness of births and deaths reported by trained HEWs for monitoring child mortality over 15 -month periods.

Methods and Findings

HEWs were trained in 93 randomly selected rural kebeles in Jimma and West Hararghe zones of the Oromia region to report births and deaths over a 15-month period from January, 2012 to March, 2013. Completeness of number of births and deaths, age distribution of deaths, and accuracy of resulting under-five, infant, and neonatal mortality rates were assessed against data from a large household survey with full birth history from women aged 15–49. Although, in general HEWs, were able to accurately report events that they identified, the completeness of number of births and deaths reported over twelve-month periods was very low and variable across the two zones. Compared to household survey estimates, HEWs reported only about 30% of births and 21% of under-five deaths occurring in their communities over a twelve-month period. The under-five mortality rate was under-estimated by around 30%, infant mortality rate by 23% and neonatal mortality by 17%. HEWs reported disproportionately higher number of deaths among the very young infants than among the older children.

Conclusion

Birth and death data reported by HEWs are not complete enough to support the monitoring of changes in childhood mortality. HEWs can significantly contribute to the success of a CRVS in Ethiopia, but cannot be relied upon as the sole source for identification of vital events. Further studies are needed to understand how to increase the level of completeness.     

Seasonality of births in nineteenth-century urban Tasmania.

The monthly distribution of births for Hobart Town, Van Diemen's Land, during the period 1839-1859 is examined. Prior research on two rural registration districts in nineteenth-century Tasmania revealed patterns of birth seasonality. The pattern was responsive to both the distinctive seasonal rhythm of regional economic activities and the birth interval and differed from the pattern for all of Tasmania in the twentieth century. Here, I argue that the aggregate monthly pattern of births in a mid-nineteenth-century urban registration district was, by contrast, not seasonal. Some seasonality was found among farmers, seamen, and dealers in foodstuffs but not in other industry groups. Class differences were not apparent. The research establishes that the seasonal distribution of mid-nineteenth-century urban births corresponds neither to nineteenth-century rural patterns nor to the patterns evident in the twentieth century.     

Defensive localism in white and black: a comparative history of European-American and African-American youth gangs

Despite the largely voluntary character of Nigerian immigration to the United States since 1970, it is not clear that their patterns of integration have emulated those of earlier immigrants who, over time, traded their specific national origins for “American” or “White” identities as they experienced upward mobility. This path may not be available to Nigerian immigrants. When they cease to be Nigerian, they may become black or African-American. In this paper, I use US Census data to trace patterns of identity in a Nigerian second-generation cohort as they advance from early school-age in 1990 to adulthood in 2014. The cohort shrinks inordinately across the period as its members cease to identify as Nigerian, and this pattern of ethnic attrition is most pronounced among the downwardly mobile – leaving us with a positively select Nigerian second generation and, perhaps, unduly optimistic assessments of Nigerian-American socioeconomic advancement.     

Demographic and socioeconomic determinants of low birth weight and preterm births among natives and immigrants in Greece: an analysis using nationwide vital registration micro-data

The present study makes use of nationwide individual-level vital registration data on the single live births occurring in Greece in 2006 to explore associations of socio-demographic factors with adverse pregnancy outcomes, using multinomial logistic regression models. The findings indicate that important risk factors associated with low birth weight preterm and intra-uterine growth retarded births (IUGR) include female sex, primiparity, age of mother over 35, illegitimacy and prior history of stillbirths, infant and child deaths. These constitute risk factors for normal weight preterm births as well, though associations with sex and primiparity in this case point to the opposite direction. Residing in large metropolitan areas is related to a greater risk of an IUGR birth. Among Greek women, educational attainment has a protective effect while housewife status is linked to higher chances of an IUGR birth. For immigrant mothers however, the opposite holds. The study also shows that normal weight preterm births form a distinct group.