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PubMed1992

Marriage conception interval.

The relationship between length of menstrual cycle and first birth interval is explored using data for 400 urban and 190 rural women in Lodha, India. The women were divided into three groups: urban women married before menarche, urban women married after menarche, and rural women married before menarche. The results indicate that "marriage-conception is delayed with longer menstrual cycles. Thus the females with longer menstrual cycle lengths appear to have a lesser chance of reproductive performances during the span of their reproductive life than those who are with shorter cycle lengths."

Asia↗
PubMedDate not supplied

How does variation in fetal loss affect the distribution of waiting times to conception?

Unmeasured variation has long been a concern in analyses of the waiting time to conception. Recent work by Heckman and Walker (1991) and Trussell and Rodriguez (1990) has underscored the fact that statistical considerations alone cannot discriminate among likely models describing the distribution. Here, we specify a single theoretically important source of heterogeneity, namely variability in intrauterine mortality, and assess its effects on the waiting times to a conception which results in a live birth. We find that the effects on the waiting times to a conception which results in a live birth. We find that the effects of variation in fetal loss are confined to the tail of the distribution. Unless variation in fetal loss is extremely large or a substantial proportion of observed waiting times are initiated at late ages, variation in fetal loss does not appear to explain much variation in conception waits. We conclude that heterogeneity in fetal loss does not explain the variation in fecundability that has been observed for first birth intervals. This conclusion supports the hypothesis that at early ages (below age 35) variation in the waiting time to a fertile conception may largely reflect the proportion of nonsusceptible couples in the population. The analyses suggest that for the purposes of testing theoretically motivated models, future efforts should be directed toward examining reproductive experience after age 35 and toward incorporating information on characteristics of the fertile period as it becomes known.

Abortion, Spontaneous↗
PubMed1994

Breast cancer incidence before age 55 in relation to parity and age at first and last births: a prospective study of one million Norwegian women.

We examined the relation between breast cancer, parity, and age at first and last births in a large national cohort of young women in Norway. We estimated relative incidence rates by Poisson regression analyses of person-years at risk with parity and age at last (most recent) birth as time-dependent variables. A total of 1,071,795 women were included in follow-up, contributing a total of 16,643,883 person-years in the age range 20-54 years. Follow-up times ranged from 1 month to 34.5 years. A total of 4,302 women were diagnosed with breast cancer during follow-up. With adjustment for age at first and last births, high parity was associated with an overall reduced risk of breast cancer (incidence rate ratio = 0.46; 95% confidence interval = 0.36-0.59 for women with five or more children vs uniparous women). Among women age 20-29 years, however, the results suggested an increase in risk with increasing parity (incidence rate ratio = 1.25; 95% confidence interval = 0.64-2.45 for women with three children vs uniparous women). The protective effect of high parity was particularly strong among women with first birth before the age of 20 years and rather weak among those with first birth at age 30 years or more. Low ages at first and last births were both associated with reduced breast cancer risk in analyses with adjustment for the other factor, with the association with age at last birth being slightly stronger.

Adult↗
PubMed1990

Age at first marriage and fertility in rural Anhui, China.

This paper examines the changing nuptiality pattern of rural China, particularly rural Anhui in relation to the planned social changes since 1949 and their effect on fertility. The data are from the 1/1000 Fertility Survey of China, conducted by the Family Planning Commission in 1982. Before the family planning programme was introduced to rural Anhui (1972), the changing nuptiality pattern was indirectly affected by the planned social changes; after 1972, the substantial increase in age at first marriage was mainly due to the family planning programme. More recently, the centrally controlled social structure is loosening, due to the economic reform and the nuptiality pattern seems to join the 1972 trend, suggesting that the dramatic change of nuptiality pattern during the early 1970s to early 1980s was a temporary one. But its effect on fertility is clear, and the shortening interval between marriage and first birth may bring difficulties for future population control in rural China.

Adult↗
PubMed1988

Socio-demographic correlates of divorce in New Zealand.

"This paper links data obtained from a one-in-five systematic sample of New Zealand divorce files covering the period 1940-78 with published marriage and birth statistics to examine socio-demographic differentials in divorce rates among couples married between 1939 and 1973. Differentials investigated are those by age at marriage, relative age of bride and groom, marital status prior to marriage, relative marital status of bride and groom, pregnancy status of the wife at marriage, timing of the first birth, religion, country of birth and socioeconomic status. Several findings of overseas studies, such as the special proneness to divorce of very youthful marriages and remarriages following previous divorces, are verified for New Zealand. After controlling for age at marriage, pregnancy does not seem to have directly increased the risk of divorce."

Birth Intervals↗
PubMed1987

Menstrual and reproductive factors and the risk of myocardial infarction in women under fifty-five years of age.

The relationship between menstrual and reproductive factors and subsequent risk of coronary heart disease was investigated in a hospital-based case-control study of 202 women with acute myocardial infarction and 374 control subjects admitted for a wide spectrum of acute conditions unrelated to any of the established risk factors for ischemic heart disease. No consistent association was observed with age at menarche or menopausal status, but women with a lifelong irregular menstrual cycle pattern were at significantly elevated risk of myocardial infarction (relative risk = 1.8, 95% confidence interval = 1.1 to 2.9). No clear trend in risk was evident with the number of livebirths, miscarriages, or induced abortions. However, women whose first pregnancy or livebirth occurred before age 20 years showed elevated risks of subsequent myocardial infarction compared with nulliparous ones (relative risks = 2.3; 95% confidence interval = 1.1 to 4.9), and there was a significant trend of increasing risk with earlier first birth. These associations were evident in both younger and middle-age women and were not explained by allowance for several identified potential confounding factors.

Adult↗
PubMed2005

Barriers to minority participation in breast carcinoma prevention trials.

BACKGROUND: Breast carcinoma prevention trials must recruit large cohorts of women who have an above-average risk of developing breast carcinoma. Recruitment for the Study of Tamoxifen and Raloxifene (STAR) trial required volunteers to complete a risk assessment questionnaire form (RAF). Women whose estimated risk of developing breast carcinoma in the next 5 years was > or = 1.67% based on the Gail model were invited to participate in STAR. Less than 4% of participants in the previously conducted P1 (tamoxifen vs. placebo) trial were minority women. We, therefore, studied barriers to minority participation in STAR among black, white, and Hispanic women who completed an RAF. METHODS: The authors analyzed the association of Gail model risk factors, education, and insurance with race/ethnicity using chi-square tests and two-sided P values. They developed logistic regression models of trial eligibility, controlling for the Gail model risk factors, education, and insurance status. RESULTS: Among 823 women who completed an RAF, white women were 10 times as likely as Hispanic women and 45 times as likely as black women to be eligible for STAR. Age at first birth (P = 0.04), having an affected first-degree relative (P < 0.0001), having had a biopsy (P < 0.0001), education (P < 0.0001), and insurance status (P < 0.0001) varied by race/ethnicity. All variables except insurance status were associated with eligibility when race was excluded from the model. In a model that included race/ethnicity, the same factors remained statistically significant. CONCLUSIONS: These findings suggested that both the race/ethnicity adjustment and socioeconomic factors were barriers to eligibility for and contribute to low minority participation in breast cancer prevention trials.

Black or African American↗
PubMed1992

Seasonality of preterm births in Japan.

Seasonal variations in the proportion of preterm births in Japan from January 1979 to December 1983 are analysed using a traditional method of time-series analysis, which divides the variation in a series into trend, seasonal variation, other cyclic change, and remaining irregular fluctuations. It is shown that the proportion of preterm births in Japan have a clear seasonal periodicity with two peaks in summer and winter. Analysis of seasonality by period of gestation shows that interesting differences in kurtosis and skewness exist between summer and winter, i.e. the summer increase in preterm births was characterized by an increase of skewness which means an extension of the lower part of the distribution. On the other hand, the winter increase was characterized by a decrease of kurtosis which corresponds to a flat-topped distribution. This result suggests that causes of preterm births might be different between the two seasons. Theoretical simulations based on actual birth data in Japan over the period, are carried out to examine how season of conception could influence seasonal variations in the proportion of preterm births. Results show that, at least for first births, seasonality in conception rates could be one explanatory factor for the observed seasonal variation in proportions of preterm births. Another analysis reveals that conception in May and June are more likely to result in preterm births in Japan.

Epidemiology↗
PubMed1997

Lactation history and breast cancer risk.

Lifetime lactation in relation to breast cancer risk was examined in a case-control study in two counties in western New York. Cases were women age 40 years and over with incident, primary, histologically confirmed breast cancer. Controls were age- and county-frequency matched, selected from New York State driver's license records (for those less than age 65 years) and from Health Care Finance Administration Records (for those age 65 or more). Included were women with at least one livebirth (253 premenopausal and 367 postmenopausal cases and 266 premenopausal and 427 postmenopausal controls). Breast cancer risk was very weakly associated with long duration of lactation among premenopausal women; the odds ratio for at least 20 months lifetime lactation was 0.50 (95% confidence interval 0.21-1.12). Among postmenopausal women, the protective effect of lactation was restricted to women with first lactation before age 25 years (odds ratio = 0.67, 95% confidence interval 0.46-0.95). However, age at first birth was highly correlated with age at first lactation. Neither insufficient milk as a reason for not breastfeeding nor having received medication to stop milk flow was associated with increased risk. These findings are in accordance with accumulating evidence that lactation may have a weak protective effect on breast cancer risk.

Aged↗
PubMedDate not supplied

[Birth center, symbols and assistance-related principles].

UNLABELLED: The first Birth Center of the Family Health Program has specific symbols. The purpose was the identification of symbols that permeate the ideas, beliefs, values, practices, and principles that guide the assistance given at the Birth Center. Ethnography was the research method; thematic oral history was the resource employed to interview obstetric nurses in the House. RESULTS: The House has the symbolic value of innovation in assisted deliveries. Humanized care to pregnant women is the principle that guide practices. FINAL CONSIDERATIONS: The symbols of the House and the care practices developed constitute a reference to the other birth centers being proposed in Brazil, and should be known by obstetrical nurses.

Birthing Centers↗
PubMed2000

Divorce in Ethiopia: the impact of early marriage and childlessness.

Forty-five per cent of first marriages in Ethiopia end in divorce within 30 years, and two-thirds of women who divorce do so within the first 5 years of marriage. This paper looks at two factors that may have an impact on the risk of divorce in Ethiopia: early age of first marriage, and childlessness within the first marriage. Data used were from the 1990 National Family and Fertility Survey conducted by the Government of Ethiopia. A total of 8757 women of reproductive age (15-49) were analysed. Life table analysis was used to determine the median age at first marriage, first birth and the median duration of marriage. Cox models were analysed to determine the differentials of divorce. The results of this analysis showed that both early age at marriage and childlessness have a significant impact on the risk of divorce. An inverse relationship was found between age at marriage and risk of divorce. Having a child within the first marriage also significantly reduced the risk of divorce. In addition, several cultural and socioeconomic variables were significant predictors of divorce.

Adolescent↗
PubMed1998

Adolescent childbearing in developing countries: a global review.

This article discusses the current levels and recent trends in the rate of adolescent childbearing, the timing of the first birth, and births to unmarried women for 43 developing countries. Differences in rates of adolescent childbearing by residence and level of education are also examined. The analysis is based on nationally representative fertility surveys. Substantial declines in adolescent fertility have occurred in North Africa and Asia, but levels are still high in some countries. Declines are beginning to occur in sub-Saharan Africa, but current levels are still high in most countries of this region, and the proportion of births to unmarried adolescents is increasing in some countries. In Latin America, where the level of teenage childbearing is moderate, declines are less prevalent and some small increases have occurred. Higher education is associated with lower rates of adolescent childbearing, but other socioeconomic changes cancel or reduce this effect in several countries.

Adolescent↗
PubMed1984

A hazard rate approach to the timing of births.

"This paper discusses two approaches that economists have taken in analyzing the timing of births. It formulates an empirical model appropriate for one of these approaches and demonstrates its usefulness using household survey data from Costa Rica. The hazard rate technique employed in this paper is a natural way of modeling a broad class of problems where the occurrence of an event is uncertain." The study also indicates that "historical data can be used to determine whether the strong trend in the relationship between regional mortality levels and the age at first birth is real or the result of inappropriate data. Additionally, data from other countries might be employed to determine whether the significant effect of male education levels on the risk of subsequent births is a general result. Finally..., the predictions of theoretical models dealing with the number and pace of births can be tested using data from younger women."

Age Factors↗
PubMed1994

The demography of Kiribati: estimates from the 1985 census.

"This paper presents an analysis of the 1985 census [of Kiribati] and compares projections made on the basis of that analysis with the 1990 enumeration. Comparison is made throughout with the estimates derived from [the] 1978 census." Information is provided on population growth and structure, child and adult mortality, marriage and first birth, and fertility.

Birth Order↗
PubMed1979

Family formation and the life cycle.

Mathematical expressions are developed for certain life cycles when only the age-specific birth and death rates are known. The probability at birth that a woman will have a specified number of children and the expected length of time spent before the first birth, between the first and the last child, and between the last child and the time of the woman's death are shown to be calculable. Expressions for the probability of at least one child outliving the mother and for the expected number of children outliving the mother are also developed and are evaluated for three selected countries with different birth and death rates to show how these life cycles depend on birth and death rates.

Birth Rate↗
PubMed1989

Conceptive delays of twin-prone mothers: a demographic epidemiologic approach.

We studied the time interval to the first birth and to the twin birth using statistical and mathematical models in two groups of mothers, those with twins and those with singletons, from the same population. We made use of a pair-matched case-control design. We treated the maternal birth cohort and parity as confounders and thus as controlled. We also investigated the sex of twin pairs as an interactive variable, employing such methods as survival curve testing and using geometric, gamma, and exponential distributions where appropriate. The expectations derived from the mathematical models yield numerical estimates of fertility components. The results suggest that unlike-sex twin-prone mothers have higher fecundity than controls when they conceive singletons. Further, fecundity appears high and unimpaired before the birth of twins. Mothers of like-sex twins experience somewhat shorter and but more variable birth intervals than corresponding controls before the birth of twins, suggesting within-group heterogeneity. Specifically, the birth of like-sex twins is preceded by low fecundity and a short period of postpartum amenorrhea. Biologically, like-sex (presumably monozygotic) twin-prone mothers have a hormonal defect related eventually to menopausal status that interferes with ovulation and perhaps with lactation. As for unlike-sex twin-bearing mothers, they probably experience a displacement of their maximum fertility potential toward early reproductive life and an extension of their menstrual life. From a methodologic standpoint, the study of the fertility of twin-prone mothers cannot proceed without estimates of the fertility components of birth intervals, as these intervals do not lend themselves to straightforward analytical interpretations by statistical analyses.

Adult↗
PubMed1991

[Life-style and demographic behavior: an application of latent class analysis].

"The aim of this study is to construct a lifestyle typology which is relevant for demographic behaviour. The concept lifestyle is defined as attitudes towards marriage, family, parenthood and the labour force participation of women. The lifestyle indicators available in the 1988 Netherlands Fertility Survey are used to construct a typology by means of latent-class-models.... The lifestyle typology can be used in two ways for projection purposes. Firstly, it can be as an explanatory variable in models for demographic behaviour. This application is demonstrated with a discrete-time hazard model for first births....Secondly, it can be used to identify innovators with respect to demographic behaviour and to quantify alternative hypotheses about the number of followers. This is demonstrated by calculating the future proportion of childlessness." (SUMMARY IN ENG)

Attitude↗
PubMed1996

Abortion and breast cancer risk.

The relationship between spontaneous and induced abortions and breast cancer risk was analyzed using data from a case-control study conducted between June 1991 and February 1994 in 6 Italian centers on 2,569 histologically confirmed incident breast cancer cases and 2,588 controls admitted to hospital for a wide range of acute, non-neoplastic, non-hormone-related diseases. One or more abortions were reported by 31% of cases and 32% of controls, corresponding to a multivariate odds ratio (OR) of 1.0 (95% confidence interval [CI], 0.8-1.1). No trend in risk was observed with increasing number of total abortions or spontaneous and induced abortions separately. No significant relationship was found between the risk of breast cancer and history of spontaneous or induced or total abortions in separate strata of age at diagnosis, number of children, time of abortion in relation to first birth and family history of breast cancer. When abortion was the outcome of the first pregnancy, the OR was 1.2 for spontaneous and 1.3 for induced abortion, in relation to women with birth as outcome of the first pregnancy, and 1.0 and 1.1, respectively, when the reference category was nulligravidae. Thus, our results indicate a lack of association between induced and spontaneous abortions and breast cancer risk.

Abortion, Induced↗