Seasonality of coitus and seasonality of birth

Seasonal variation of birth rates has been observed in every population in which it has been studied. Many hypotheses have been advanced to account for the variation, including seasonal variation in frequency of coitus. This relationship is known to be true for other primates, but seasonal variation in coital rate has not been previously documented in man.This paper presents over one hundred woman-years of data on coital rates from about .fifty white, mostly well-educated, premenopausal, married, husband-present volunteers. Seasonal fluctuations were seen in coital rates, of about the same magnitude as seasonal variations in the white birth rates reported for New York City, 1962-64; for the United States, 1963; and for the highest socioeconomic quintile census tracts, Baltimore, 1952-56. However, shifting the birth rates back forty weeks to approximate conception dates revealed no association with the observed coital rates.If the pattern presented has great generality, seasonal variations in births cannot be explained by seasonality of coitus.     

High foetal mortality and birth intervals

Abstract Studies of birth intervals have generally separated the process into: (1) the period of infertility following a pregnancy termination; (2) the length ofthe interval from the end of the infertile period to the next conception (which reflects the probability of conception), and (3) the average duration of pregnancy for both live births and foetal deaths.(1) Empirically derived intervals between successive live births average from 19 to 30 lunar months(2) (Table 1), depending upon the population studied and the birth order.(3) Estimates of conception rates using birth intervals data require some estimate of the extent to which foetal wastage increases the birth interval.     

The effect of marital status at first birth on marital dissolution among adolescent mothers

The sequencing of marriage and first birth was expected to play an important role in the stability of marriage among adolescent mothers. We hypothesized that adolescent women who married prior to conception would have the lowest rates of marital disruption, followed by those who married between conception and birth. Adolescent women who gave birth prior to marriage were expected to suffer the highest rates of marital dissolution. The results provide partial support for our hypotheses. There is little difference in the probability of separation between adolescent mothers who had a postmarital conception and those who had a premarital conception but married before the birth. Having a premarital birth, however, significantly increases the probability of marital dissolution. We also hypothesized that marital status at first birth would have less effect on the probability of marital dissolution for blacks than for whites. This, too, is generally supported by our findings. Among black females, those with a premarital birth are the first to suffer a marital disruption, but by the end of ten years there is little difference in the probability of separation among the three marital status groups. In contrast, among white females, those with a premarital birth are the first to experience a disruption, and this differential persists over all subsequent marriage duration intervals. Thus, the sequencing of marriage relative to birth has similar short term effects for whites and blacks, but the effect for blacks is evident only in the short term. Ten years after the marriage, black adolescent mothers have similar rates of marital stability regardless of the sequencing of marriage. This is consistent with the findings of previous research and with our hypothesis; with the black family pattern of lower rates of marriage, higher rates of illegitimacy and higher divorce rates, the sequencing of marriage has no long lasting consequences on marital stability. Finally, our predicted decline in the effect of marital status at first birth over historical time also finds partial support. For white females there has been a change in the effect of marriage-first birth sequencing on separation over time. In the period encompassed by the women in our study, white adolescent mothers who married subsequent to the birth have been the most likely to experience a separation at all marriage duration intervals, but this differential narrows as age at interview declines. Among black females there has been no change in the effect of a premarital birth over time.(ABSTRACT TRUNCATED AT 400 WORDS)     

On some probability distributions for forward birth interval

Statisticians from Varanasi, India have proposed 2 mathematical models for forward birth interval which are more realistic than past models. For example, past models have assumed fecundability to be constant throughout a woman's reproductive life. On the other hand, the proposed models assume fecundability changes with parity. Further the statisticians use all types of marital durations making their models usable even for short marriage durations. The 1st model uses a parity specific model to develop a model for forward birth interval regarless of parity. The statisticians also include moments of the 1st and 2nd models as expressed for the rth order raw movement of these models to estimate some of their parameters. These models can be used to conduct prospective surveys of family planning programs since birth intervals can best evaluate the effect of these programs. These models have not yet been advanced enough to follow women over a fixed period, however. They only observe women until the last woman conceives. The statisticians do not apply the models to parity specific data because they were not available. Yet they do run the models with parities 0 and 1. The models reveal that the mean length of forward birth interval is strongly influenced by the conception rate which the woman has at the time of the survey. Thus, if women with a certain parity in a community begin an effective family planning method on the survey day, which in effect would reduce the prevailing conception rate, that method would significantly postpone the next live birth.     

Factors Affecting Birth Rates Among Black Women 20--24 Years of Age: A Trend Analysis (January 1972--March 1992)

This research provides a multivariate explanation of monthly (N = 243) birth rate variation for African-American women 20--24 years of age using time series analysis. The research explains both seasonal and intermediate variation in these birth rates. The independent variables were selected for their relationship to: economic understandings of fertility; developing understandings of the relationship of photoperiod to reproductive functioning; routine activity theory; and the relationship of birth rates to quality of life perspectives. The findings of this research are interpreted with respect to important developments and understandings in the quality of life literature. Concepts of 'compensatory validation' and 'contextual compatibility' are derived from quality of life understandings and Rainwater's (1974) concept of 'validating activities'. The previously identified importance of domains of intimacy, sexual activity and family life (Cummins, 1996; Alfonso et al., 1996) are related to empirical findings concerning the conception of children and incorporated into these theoretical concepts. Nine explanatory variables were selected. Theoretical, research and policy implications are summarized.     

The temporal relationship of marriage,conception, and birth in Massachusetts

An investigation into the timing of first births in relationship to the date of marriage in Massachusetts confirmed the finding of previous national and local birth timing studies that first births likely to have been conceived before the marriage of their parents constitute a substantial proportion of all first births. The differential frequency of premaritally conceived births among various subgroups appeared to account for the variation noted in the overall timing patterns of first births after marriage. Data were gathered through linkage of certificates of birth of a sample of legitimate first children with the marriage record of their parents. Analysis of the marriage-first birth interval by maternal age and race, type of marriage ceremony, and occupation of the bride and groom were conducted and comparisons with previously published data were made. Separate consideration was given to the frequency and characteristics of those births likely to be premaritally conceived and those likely to have been conceived after the wedding.     

Age-parity-specific birth rates and birth probabilities from census or survey data on own children

The ‘own-children’ method is a census- or survey-based reverse-survival technique for estimating age-specific birth rates for years previous to enumeration. In this paper it is extended to estimate birth rates and birth probabilities by parity as well as by age. The refined method is tested for accuracy by comparing ‘own-children’ estimates of age-parity-specific birth probabilities for the United States in 1969 with parallel estimates obtained by the method used in Vital Statistics of the United States. The ‘own-children’ estimates give relatively lower values at ages 15-19 and higher values at ages above 40, but compare well in between. The discrepancies are probably due mainly to adoption of illegitimate children of young mothers by older women. The ‘own-children’ estimate of the total fertility rate is very close to the published vital statistics estimate.     

Stabilization,birth waves,and the surge in the elderly*

Substantial regularities characterize the transition to stability that follows a shift from one set of vital rates to another. The new vital, rates interact with the population's initial age composition and generate birth waves whose amplitude and attenuation depend on the ratio of ultimate to initial growth and on the new pattern of stable net maternity. A greater change in growth and a later stable net maternity pattern produce larger fluctuations in the number of births. Stabilization begins at the youngest ages and proceeds upward. Sixty years after the shift, the birth waves have largely disappeared and the proportion under age 15 approximates the stable level implied by the new rates. Those patterns are manifest in the stabilization of both observed and Coale‐Demeny model stable populations.

When fertility falls, the new stable population has a larger fraction at all ages above (approximately) 30, with greater changes characterizing the extremes of life. Fifteen years after the fall, there is a trough in the number at ages 0–14. Sixty years after the fall, when the largest pre‐decline cohort is age 60–74 and the smallest post‐decline cohort is age 45–59, there is a surge in the relative size of the elderly population. Thus after two generations, the birth waves produced by a rapid decline in fertility accentuate the effects of population aging.     

Declining birth rates and growing populations

Excitement over declining fertility in the Third World needs caution for several reasons. First, it is now too late to solve the world's population problem. Second, the common belief that the birth decline is widespread and is affecting virtually all developing nations goes beyond the data. Third, the notion that birth rates are declining with great speed is not true when the rate is measured against either urbanization or mortality decline. Fourth, a sample of countries indicates that the decline is now slowing rather than accelerating. Fifth, the idea that the declines are due mainly to family planning, and can therefore be assured of continuance in the future, seems unwarranted.Revised version of a paper given at the annual meeting of the American Sociological Association, San Francisco, September 7, 1982.     

Preliminary inquiry into the difference in sex ratio at birth in China]

Based on population statistics from China's 2nd and 3rd national censuses, China's unusually high male/female birth rates are examined. It appears that the lower male/female birth rates are generally found in China's minority-populated autonomous regions. Xizang Autonomous Region (Tibet) has the nation's lowest male/female birth ratio of 101.3; the highest ratio, 112.5, is in Anhui province; the national average for 1981 was 108.47. Although geographic, socioeconomic, and other factors may be attributed to regional differences, it is maintained that the high male/female birth rate is universal throughout China. The significant difference between the relatively high male/female birth rate in China's urban areas in 1981 (109.9), and the lower rate in the rural areas (107.6) is challenged by the author, who suggests that China's urban statistics are unquestionably more reliable than the rural statistics. The author suggests that factors such as the importance of raising male offspring, China's traditionally male-dominated family system, and the desire for male farm workers is strongest in China's rural sector. The current male/female birth rate is not a recent trend; prior to 1949, the male/female birth rate ranged from 110 to 115.     

Stabilization,birth waves,and the surge in the elderly

This study examines the transition of a population to stability following a shift to a new fixed set of vital rates. Specifically, the authors develop a simple discrete population model and use it to derive an explicit solution for the birth trajectory. "The new vital rates interact with the population's initial age composition and generate birth waves whose amplitude and attenuation depend on the ratio of ultimate to initial growth and on the new pattern of stable net maternity. A greater change in growth and a later stable net maternity pattern produce larger fluctuations in the number of births. Stabilization begins at the youngest ages and proceeds upward. Sixty years after the shift, the birth waves have largely disappeared and the proportion under age 15 approximates the stable level implied by the new rates. Those patterns are manifest in the stabilization of both observed and Coale-Demeny model stable populations." (SUMMARY IN FRE)     

The relationship of the crude birth rate and its components to social and economic development

Using well-known techniques of regression analysis, we decompose the crude birth rate into six analytical components, indicating illegitimacy, the marriage rate, legitimate fertility, and sex and age composition. All the components except sex structure are important in determining differences in crude birth rates across countries of the world. The model is elaborated by showing how economic development affects the crude birth rate through its basic demographic components.     

Caesarean section by country of birth in New South Wales,Australia

ObjectiveTo determine rates of caesarean section by country of birth and by obstetric risks.MethodsWe analysed the New South Wales Perinatal Data Collection data of women giving birth between January 2013 and December 2015. Obstetric risk was classified using the Robson’s 10-group classification. Multilevel logistic regression with a random intercept was used to measure the variation in caesarean section rate between immigrants from different countries and between regional immigrant groups.ResultsWe analysed data from 283,256 women, of whom 90,750 had a caesarean section (32.0%). A total of 100,120 women were born overseas (35.3%), and 33,028 (33.0%) had a caesarean section. The caesarean section rate among women from South and Central Asia ranged from 32.6% for women from Pakistan to 47.3% for women from Bangladesh. For South East Asia, women from Cambodia had the lowest caesarean section rate (19.5%) and women from Indonesia had the highest rate (37.3%). The caesarean section rate for North Africa and the Middle East ranged from 28.0% for women from Syria to 50.1% for women from Iran. Robson groups that accounted for most of the caesarean sections were women who had previous caesarean section (36.5%); nulliparous women, induced or caesarean section before labour (26.2%); and nulliparous women, spontaneous labour (8.9%).ConclusionsThe caesarean section rate varied significantly between women from different countries of birth within the same region. Women from some countries of birth had the higher caesarean section rates in some Robson groups.     

Vaginal birth after caesarean: Views of women from countries with low VBAC rates

Problem and background

Vaginal birth after caesarean section is a safe option for the majority of women. Seeking women’s views can be of help in understanding factors of importance for achieving vaginal birth in countries where the vaginal birth rates after caesarean is low.

Age at last birth and its components

This paper examines the ways in which the behavior of twentieth century cohorts of American women changed simultaneously in the three components of fertility that determine age at last birth--age at first birth, spacing between subsequent births, and parity progression ratios of subsequent births--to produce changes in the timing of the completion of childbearing. It decomposes changes in the mean age at last birth among cohorts and between whites and nonwhites to changes in these three components. To perform these analyses, we developed and applied a method to estimate the distributions and means of ages and last births, birth intervals, and parity progression ratios from age- and parity-specific fertility rates available from vital statistics data. Results show that the cohorts increased and decreased their age at first birth, birth intervals, and parity progression ratios of lower and higher birth orders in almost every possible combination so as to achieve a relatively young age at final birth.     

Giving birth after caesarean: Identifying shared preferences among pregnant women using Q methodology

BackgroundCaesarean rates are rising worldwide, the main contributor being the elective repeat caesarean. During the past decades, rates of vaginal birth after caesarean dropped considerably. This requires insight in women’s preferences regarding giving birth following a previous caesarean.AimTo gain a better understanding of women’s values and preferences regarding the upcoming birth following a previous caesarean. Using Q methodology, this study systematically explores and categorises their preferences.MethodsQ methodology is an innovative research approach to explore and compare a variety of viewpoints on a certain subject. Thirty-one statements on birth after caesarean were developed based on the health belief model. Thirty-six purposively sampled pregnant women with a history of caesarean ranked these statements from least to most important. By-person factor analysis was used to identify patterns which, supplemented with interview data, were interpreted as preferences.FindingsThree distinct preferences for giving birth after a caesarean were found; (a) “Minimise the risks for me and my child”, giving priority to professional advice and risk of adverse events, (b) “Seek the benefits of normal birth”, desiring to give birth as normal as possible for both emotional and practical reasons, (c) “Opt for repeat caesarean”, expressing the belief that a planned caesarean brings comfort.ConclusionsPreferences for birth after caesarean vary considerably among pregnant women. The findings help to understand the different types of information valued by women who need to decide on their mode of birth after a first caesarean.     

Nonmarital Childbearing in Russia: Second Demographic Transition or Pattern of Disadvantage?

Using retrospective union, birth, and education histories that span 1980–2003, this study investigates nonmarital childbearing in contemporary Russia. We employ a combination of methods to decompose fertility rates by union status and analyze the processes that lead to a nonmarital birth. We find that the increase in the percentage of nonmarital births was driven mainly by the growing proportion of women who cohabit before conception, not changing fertility behavior of cohabitors or changes in union behavior after conception. The relationship between education and nonmarital childbearing has remained stable: the least-educated women have the highest birth rates within cohabitation and as single mothers, primarily because of their lower probability of legitimating a nonmarital conception. These findings suggest that nonmarital childbearing Russia has more in common with the pattern of disadvantage in the United States than with the second demographic transition. We also find several aspects of nonmarital childbearing that neither of these perspectives anticipates.     

Regression analysis of the relationship between the birth rate and proportion of first order births in 1981]

Generally speaking, various fertility indicators such as the birth rate, average fertility rate, and total fertility rate have a close relationship. Various regression analyses have also been made by using different data on population statistics to describe their internal relationships. A regression analysis of the relationship between the birth rate and proportion of first order births, however, has not been made. Data collected by family planning staff at various places show that the places with a high rate of first order births normally have a lower birth rate, and the places with a low rate of first order births very often have a high birth rate. From here we may find that the proportion of the first order births is moving in two opposite directions, and there is no determined relationship between them. It is impossible to use one indicator to calculate the other's indicator. Only a regression analysis can be made to study the relationship between the two. The birth rate and proportion of first order births in 1981 showed some negative relationship, but the use of a regression equation should still be restricted. The regression equation between the birth rate and proportion of first order births may reflect a correct relationship when the region and the number of first order births are fixed. Therefore, any factor which has an impact on the number of first order births also has an influence on the use of regression equation.     

Prospective study of birth interval dynamics in rural Bangladesh

Abstract A group of 209 married, fecund women in rural Bangladesh were studied prospectively for 24 months from 1969 to 1971 to define some of the biological and sociological factors relating to fertility performance. These women were selected from a larger study population of 112,000 that had been followed with a daily house-to-house vital registration programme since 1966. The selected women were interviewed bi-weekly and were asked questions about menstruation, pregnancy, lactation, husband's occupational absences, and monthly urine tests for pregnancy were taken. The results for 193 non-contracepting women revealed that the seasonal pattern of births previously observed in this population could be associated with a corresponding seasonal pattern of conceptions and that this was due to a seasonal trend in fecundability. The highest conception rates were in the coolest months of the year. Post-partum lactational amenorrhoea was very prolonged, averaging 17 months for women with a surviving child. The appearance of the first post-partum menstrual flow (onset of ovulation) also had a seasonal trend which could not be adequately explained. The median waiting time to conception, once menstruation had resumed was eight months. This interval was influenced by seasonal fluctuations, as well as by the age of women and by husbands' absences. The foetal wastage rate was 15·0 per 100 conceptions, with 62 per cent of the foetal losses occurring during the second month of gestation. Overall, the average birth interval was 33 months, with the prolonged lactational amenorrhoea accounting for almost 45 per cent of this interval. From the Department of Population Dynamics, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland 21205.     

Development of birth registration and birth statistics in the United States

The registration of vital events in the United States has always been under the authority of State and local areas. The preparation of national birth statistics has been made possible through a co-operative working arrangement between the Federal Government and the States. This paper traces the development of registration systems in the United States from colonial days to the present period. The absence of adequate registration systems throughout the country, during the nineteenth century, led to the use of data collected in the decennial population censuses of 1850–1900 for estimating birth rates. This procedure was abandoned because of the unreliability of the results. Steps leading to the formation of the national birth-registration area in 1915, when it included ten States and the District of Columbia, and. activities resulting in its completion in 1933 are discussed.

A major portion of the paper outlines the nation-wide test of birth-registration completeness conducted in 1940 in conjunction with the decennial census of population. Important results of the test are presented, and the methodology is explained. A similar test is being carried out in 1950. Data derived will be used to focus attention on local areas requiring registration promotion. Correction factors for statistical series based on registered events will also be obtained. The final section of the paper indicates the steps States are taking to improve quality of reporting on the birth record. Changes in the content of the standard certificate of live birth since 1915 are summarized and the statistics tabulated from birth certificates detailed.