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PubMed1996

Age at any birth and breast cancer in Italy.

To provide quantitative information on the role of age at any birth for breast cancer risk, we analyzed data from a cooperative Italian case-control study conducted between 1991 and 1994 on 2,569 incident, histologically confirmed breast cancer cases and 2,588 controls in hospital for acute, non-neoplastic, non-gynecological conditions. A single logistic model was fitted, including terms for number of births, age at each birth and at menarche, plus age and center. Age at first birth was the strongest reproductive determinant of subsequent breast cancer risk, with an estimated increase of 4.6% per year of delay of first birth. This was similar to the influence of age at menarche (4.7% decrease in risk per year of delay of menarche). Ages at subsequent births had an independent effect on breast carcinogenesis, with an estimated 0.7% increase in risk per year of delay. Multiparity showed also an independent protection on breast cancer risk, and a protective effect of parity > or = 3 was evident in all strata of age at first birth: the odds ratio was 0.81 for 3 births and 0.70 for > or = 4 births. However, the effect of parity was determined by the age of occurrence of various births.

Adolescent↗
PubMed1990

Childbearing in marriage and mortality from breast cancer in Norway.

The relationship between childbearing and mortality from breast cancer has been studied in a cohort of 822,593 currently married Norwegian women with information on parity from the Census in 1970 and follow-up till 1985. All age groups of parous women showed significant trends of decreasing mortality rates with increasing parity. Nulliparous women had the same mortality rates as uniparous women in all age groups. In a stratified analysis, for age group 45-74 years, the relative risk for uniparous women was between 3.8 and 4.5 dependent on age at first birth compared to women with 8-9 children, age at first birth before the age of 25 and last birth after the age of 30 years. In a multivariate analysis age and parity were stronger risk factors than age at first birth, while age at last birth was nonsignificant. Among women 45-74 years the population attributable risk of breast cancer mortality due to childbearing was 72%, using women with 8-9 children as the reference group. The use of different definitions of reference group for parity is discussed.

Adult↗
PubMedDate not supplied

Early childbearing and children's achievement and behavior over time.

CONTEXT: Compared with children of older women, children of women who had their first birth during their teens have long been believed to be at higher risk for a host of poor health, social and economic outcomes. Recent studies have failed to confirm this belief, but none have taken into account whether children's outcomes or the effects of early childbearing on those outcomes have changed over time. METHODS: Data from the National Longitudinal Survey of the Labor Market Experience of Youth and the Panel Study of Income Dynamics are used to separate the influence of changes from the 1960s through the 1990s in children's experiences from the effect of mother's age at first birth. RESULTS: Multivariate analyses controlling for social and demographic characteristics show that among children born to women from a particular birth cohort, those whose mothers first gave birth in their teens have significantly lower scores on a set of four achievement tests and significantly higher scores on a behavior-problem index than do children whose mothers delayed childbearing. However, when changes over time in children's outcomes and in the effect of early childbearing on those outcomes are taken into account, children born to women who began childbearing early score significantly worse than those whose mothers delayed their first birth on the behavior-problem index, but on only one achievement test. CONCLUSIONS: Comparisons by age at first birth among women born in the same period may misestimate the effects of early motherhood. Whether early childbearing's effects on children are overestimated or underestimated depends on whether test scores are rising or falling. Policymakers should be cautious in making decisions based on studies that do not take time trends into account.

Adolescent↗
PubMed2002

Breast cancer risk factors and age at diagnosis: an Icelandic cohort study.

An increasing number of studies indicates that the strength and even direction of association between breast cancer and established risk factors differ according to the woman's age when she develops the disease. This was studied in the setting of a population based cancer registry using a databank with information on age at menarche, parity, age at first birth, oral contraceptive (OC) use, lactation, height and weight. From a cohort of 80.219 women attending population-based cervical and breast cancer screening in Iceland, 1120 cases were identified, aged 26-90 years at diagnosis and 10,537 controls, individually matched to the cases on birth year and age when attending. Information given at last visit before diagnosis was used in the analysis, applying conditional logistic regression. Odds ratios and statistical strength of relationships varied according to age at diagnosis for age at first birth, number of births, duration of lactation, height and weight. The decreased risk associated with young age at first birth and increasing duration of breast feeding became less pronounced with advancing age at diagnosis. A reduced risk associated with an increasing number of births was not detected in women diagnosed under the age of 40. An increased risk associated with giving first birth after 30 years of age was mainly detected in women who had only given 1 birth and were diagnosed under the age of 40 (OR = 7.06 95% CI = 2.16-23.01). A positive association with height and especially with weight was confined to women diagnosed after the age of 55. The results confirm that age at diagnosis should be taken into account when studying the effects of breast cancer risk factors.

Adult↗
PubMed2002

Grand multiparity and incidence of endometrial cancer: a population-based study in Finland.

The hormonal background of endometrial cancer is insufficiently characterised. We investigated the significance of parity, age at first birth, intensity between births, length of time from the first to the last birth and length of delivery-free premenopausal period in a cohort of grand multiparous (GM) women, i.e., women with at least 5 births. Data of the Population Register of Finland (86,978 GM-women) and the population-based Finnish Cancer Registry were combined. Standardised incidence ratios (SIRs) were calculated by dividing the number of observed cancer cases by the expected number based on the national incidence rates. Multivariate relative risks (RRs) were estimated by Poisson regression analysis. The SIR for endometrial cancer among GM-women was low [419 cases; SIR=0.57, 95% confidence interval (CI) 0.52-0.63]. The RR of endometrial cancer was 0.58 (95% CI 0.34-0.97) among women giving their first birth at an age of more than 30 years compared to women with first birth before the age of 20. In ages 50+ (94% of endometrial cancer cases), the RR for women with at least 8 births was 0.63 (95% CI 0.44-0.92) compared to those with 5 births, and those with a birth period of 20+ years had RR=0.57 (95% CI 0.34-0.96) compared to those with a period of <10 years, while prolonged average intensity between births showed only a small protective effect. The RR of endometrial cancer also correlated with the length of premenopausal delivery-free period (RR = 0.61, 95% CI 0.44-0.86) for women with a short (<10 years) period compared to women with a long (>15 years) period. Our findings, that a large number of births, old age at first birth, a long birth period and a short premenopausal delivery-free period reduced the risk of postmenopausal endometrial cancer of GM-women, emphasise the protective role of progesterone and the stimulatory role of estradiol in the hormonal background of this disease.

Adenocarcinoma↗
PubMed1994

Geographical differences and time trends in the seasonality of birth in Japan.

Seasonal variations of births in six different prefectures in Japan are analysed using Vital Statistics from 1974 to 1983. First births show a bimodal pattern with two peaks, one in winter (December-February) and the other in summer to early autumn (August-September). The seasonality of first births is statistically significantly correlated with the seasonality of marriages with 9 + 12*n (n = 0, 1, 2, 3) lag months. For subsequent births, the seasonal pattern is unimodal and there is also a geographical trend in seasonality of these births with a late spring peak in the northernmost prefecture of Japan giving way to an early autumn peak in the southernmost prefecture. These findings suggest that seasonal variations in marriage play some role in the seasonality of first births, while other features such as environmental factors could be associated with the seasonal variations of subsequent births. Changes in the seasonality of both births and marriages over time suggest that the modernization of Japanese society after the second World War could be responsible for the drastic changes in the pattern and degree of seasonality of births.

Analysis of Variance↗
PubMed2003

Interpregnancy interval and risk of preterm birth and neonatal death: retrospective cohort study.

OBJECTIVE: To determine whether a short interval between pregnancies is an independent risk factor for adverse obstetric outcome. DESIGN: Retrospective cohort study. SETTING: Scotland. SUBJECTS: 89 143 women having second births in 1992-8 who conceived within five years of their first birth. MAIN OUTCOME MEASURES: Intrauterine growth restriction (birth weight less than the 5th centile for gestational age), extremely preterm birth (24-32 weeks), moderately preterm birth (33-36 weeks), and perinatal death. RESULTS: Women whose subsequent interpregnancy interval was less than six months were more likely than other women to have had a first birth complicated by intrauterine growth restriction (odds ratio 1.3, 95% confidence interval 1.1 to 1.5), extremely preterm birth (4.1, 3.2 to 5.3), moderately preterm birth (1.5, 1.3 to 1.7), or perinatal death (24.4, 18.9 to 31.5). They were also shorter, less likely to be married, and more likely to be aged less than 20 years at the time of the second birth, to smoke, and to live in an area of high socioeconomic deprivation. When the outcome of the second birth was analysed in relation to the preceding interpregnancy interval and the analysis confined to women whose first birth was a term live birth (n = 69 055), no significant association occurred (adjusted for age, marital status, height, socioeconomic deprivation, smoking, previous birth weight vigesimal, and previous caesarean delivery) between interpregnancy interval and intrauterine growth restriction or stillbirth. However, a short interpregnancy interval (< 6 months) was an independent risk factor for extremely preterm birth (adjusted odds ratio 2.2, 1.3 to 3.6), moderately preterm birth (1.6, 1.3 to 2.0), and neonatal death unrelated to congenital abnormality (3.6, 1.2 to 10.7). The adjusted attributable fractions for these associations were 6.1%, 3.9%, and 13.8%. The associations were very similar when the analysis was confined to married non-smokers aged 25 and above. CONCLUSIONS: A short interpregnancy interval is an independent risk factor for preterm delivery and neonatal death in the second birth.

Birth Intervals↗
PubMedDate not supplied

Education and timing of parenthood among Canadian women: a cohort analysis.

This research examines factors associated with the timing of first birth in Canada, focusing primarily on the role of women's educational attainment. Proportional hazards modelling techniques are applied to data from the 1984 Canadian Fertility Survey (CFS) in order to determine how educational attainment, estimated as close as possible to the date of first birth, influences the timing of first birth and whether the importance of this variable varies according to age cohorts. The results suggest that among a number of variables useful for distinguishing different levels of risk, educational attainment proves to be the most important predictor in the model. Education exerts a substantial positive influence on birth timing for women of all age groups. As expected, moreover, significant cohort differences are also evident, with the greatest to the smallest impact on the risk from the youngest to the oldest cohorts. These clear-cut cohort differences indicate a fundamental change in the effects of education over time, a trend most likely resulting from substantial changes in both the content and social significance of formal schooling during the past few decades.

Adolescent↗
PubMed1996

Nurses' health study: log-incidence mathematical model of breast cancer incidence.

BACKGROUND: In 1983, Pike et al. developed a mathematical model to quantify the effects of reproductive risk factors on the incidence of breast cancer. In 1994, we modified that model to correct some deficiencies in the original model, including a lack of terms for spacing of births and an inability to easily accommodate births after age 40 years. Our extended Pike model, while improving on the original, still has serious disadvantages, such as difficulty in translating model parameters into relative risks (RRs) and an incomplete fit to data that slightly overestimated incidence for premenopausal women with an early age at first birth and that underestimated incidence for post-menopausal women with a late age at first birth. PURPOSE: We undertook both the development of a new mathematical model to quantify the effects of reproductive risk factors on breast cancer incidence and validation of the model. METHODS: A new log-incidence model of breast cancer incidence was developed using nonlinear regression methods, and a study population consisting of 89,132 women in the Nurses' Health Study from which a total of 2249 incident cases of breast cancer were identified. Subjects were followed from the return of the 1976 Nurses' Health Study questionnaire until June 1, 1990, or until the last questionnaire was returned, until the development of any cancer, or until death, yielding 1,148,593 person-years of follow-up. The log-incidence models were fitted using iteratively reweighted least squares analysis. RESULTS: The log-incidence model provided a better fit to that data than the extended Pike model, with parameter estimates interpretable in terms of RRs. This new model can be fitted using standard commercially available statistical software. In the model, younger parous women are generally at slightly higher risk than nulliparous women, which is true for both the observed and expected RRs, and older parous women, aged 55-64 years with an early age at first birth, are at lower risk than nulliparous women,while older women with a late age at first birth are at substantially higher risk than nulliparous women. CONCLUSION: Log-incidence models, such as this one, provide an efficient framework for modeling the effect of lifestyle risk factors on breast cancer incidence that may be specifically targeted to certain time periods of a woman's reproductive life.

Adult↗
PubMedDate not supplied

Factors associated with inadequate prenatal care during the second pregnancies among African-American women.

A longitudinally linked data set for Georgia was used to identify characteristics, including previous prenatal care use and complications at the first birth, associated with prenatal care use in the second pregnancy among 8,224 African-American women. More than 70% of the women who were < 25 years of age at their first birth (younger women) and almost 40% of women who were > or = 25 years at their first birth received inadequate care with at least one of their first two births. Women who received inadequate care in their first pregnancy were more likely to receive inadequate care in their second pregnancy than women who received adequate care in their first pregnancy. Younger women with a history of a stillbirth, neonatal death, or vacuum extraction were less likely to receive inadequate care in their subsequent pregnancy. Although this study was not able to evaluate the content of prenatal care, it suggested that many African-American women may not receive sufficient care to prevent adverse pregnancy outcomes. Women who receive inadequate care in their first pregnancy must be targeted for interventions that help them overcome economic, situational, or attitudinal barriers to receiving adequate care in their next pregnancy.

Adolescent↗
PubMed1995

Reproductive factors and colon cancer: the influences of age, tumor site, and family history on risk (Utah, United States).

The Utah (United States) Population Database was used to evaluate the associations between reproductive factors and colon cancer risk and the impact that family history, age at diagnosis, and tumor site have on these associations. From the cohort of (White) women in the database, all first-primary cases of colon cancer (n = 819) and controls who had complete fertility information (n = 3,202) were examined. The majority of tumors (68.6 percent) among women diagnosed at age 64 years or less were in the distal segment of the colon, while among women 65 or older, the majority of tumors (55.7 percent) were proximal. Women diagnosed before age 65 had a lower risk of colon cancer with increasing numbers of liveborn children (odds ratio [OR] = 0.6, 95 percent confidence interval [CI] = 0.3-0.9 for women with five or more children compared with women with one or two children). A long interval between first and second births (first birth-interval) was associated with increased risk of tumors in the distal segment of the colon (OR = 1.4, CI = 1.0-2.0) and among women diagnosed before age 65 (OR = 1.6, CI = 1.0-2.5); a longer, average birth-interval was associated with increased risk of proximal tumors (OR = 1.5, CI = 1.1-2.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Pooled analysis of 3 European case-control studies: I. Reproductive factors and risk of epithelial ovarian cancer.

The role of reproductive factors in the aetiology of epithelial ovarian cancer has been re-assessed in a meta-analysis of 3 hospital-based case-control studies conducted in Europe (i.e. Italy, the United Kingdom and Greece), providing a total dataset of 1,140 cases and 2,724 controls. Multiple logistic regression models were used to obtain relative risk (RR) estimates adjusted for study centre, age, socio-cultural indicators, age at menopause, and oral contraceptive use. The risk decreased with increasing number of births and the trend in risk was significant (chi 2(1) = 7.50, p less than 0.01). In comparison to nulliparous women, those who reported 4 or more births had a 40% reduction in risk of ovarian cancer (RR = 0.6, 95% confidence interval, CI: 0.4-0.8). An RR estimate of 1.4 (95% CI: 1.1-1.7) as found, overall, for age of 35 or more at first birth compared to age of 25 or less at first birth. In each stratum and overall, nulliparous women did not appear to be at increased risk compared to those who delayed birth of their first child until age 35 or more. In each study, as well as in the overall dataset, an inverse association between number of abortions and ovarian cancer risk emerged. Overall, the inverse relationship was highly significant, RR estimates for 1 and 2 or more abortions, as compared to none, being 0.9 (95% CI: 0.8 and 1.1) and 0.7 (95% CI: 0.6-0.9) respectively. The effects of parity, age at first birth and number of abortions emerged consistently in various strata of study centre and age.

Abortion, Spontaneous↗
PubMed1996

Malignant melanoma: reduced risk associated with early childbearing and multiparity.

Pigmentary changes during pregnancy and sex-specific differences in incidence patterns of cutaneous malignant melanoma (CMM) suggest that sex hormones may be involved in the development of CMM. We explored possible associations between childbearing and the risk of CMM in a case-control study "nested' in a nation-wide cohort. A total of 4,779 incident cases of CMM in women aged 24-65 were compared with 23,888 individually age-matched controls. Delayed childbearing was associated with an increased risk of CMM, corresponding to approximately 16% per 5 years. Parous women had a significantly lower risk of CMM compared with nulliparous women; in univariate analysis there was an 8% reduction in risk for each additional birth (odds ratio = 0.92; 95% confidence interval = 0.89-0.95). In multivariate analyses the risk of CMM was best explained by a model including both age at first birth and parity. Age at first birth was the most important variable. Time since most recent birth was unrelated to risk of CMM. These findings indicate that early childbearing and multiparity reduce the risk of CMM. Conceivable explanations are hormonal changes induced by childbearing, enhanced immunologic activity via exposure to fetal antigens during pregnancy, or long-lasting effects of pregnancy-associated hyperpigmentation. Our results need confirmation in studies with proper adjustment for confounding; less sun exposure in young mothers and high parity women may represent an alternative explanation but is unlikely to explain entirely the twofold difference in risk found between extreme categories of age at first birth and parity.

Adult↗
PubMed1985

Reproductive and hormonal factors and breast cancer in a Northern Italian population.

Between January 1980 and March 1983, data were collected to evaluate risk factors for breast cancer in a case-control study based on 368 women with breast cancer admitted to the General Hospital of Pordenone (a district in North Eastern Italy with a particularly high breast cancer mortality rate), and 373 age-matched controls. Nulliparity or low parity, late age at first birth and later menopause were associated with an increased risk of breast cancer. The elevated risk associated with nulliparity could be almost completely explained by marital status, thus pointing to a specific protection given by parity, rather than some putative influence of infertility or subfertility in breast cancer cases. Likewise, risk did not vary materially according to history of abortions when marital status was controlled for. Increased risk associated with later age at first birth, on the other hand, was not accounted for by marital status or parity. The population studied, though frequently multiparous, showed late average at first birth: this might, at least partly, explain its high mortality rate from breast cancer. The risk estimate was higher if menarche occurred below age 15; however, there was no evidence of a trend for the relative risk to rise with lower age at menarche. The use of oral contraceptives or other female hormones (such as oestrogen replacement therapy) did not appear to be related to the risk of breast cancer. The role of the major menstrual and reproductive variables considered (age at menarche, parity, age at first birth) was apparently stronger in pre-menopausal women, thus suggesting an influence of these factors (and possibly, their hormonal correlates) on one of the latter stages of the process of carcinogenesis.

Abortion, Spontaneous↗
PubMed2006

Pregnancy history and incidence of melanoma in women: a pooled analysis.

There is evidence that pregnancy history including age at first birth and parity may play a role in risk of cutaneous melanoma in women, although, epidemiological findings are inconsistent. We conducted a collaborative analysis of these factors using the original data from ten completed case-control studies (2391 cases and 3199 controls), and assessed the potential confounding effects of socioeconomic, pigmentary, and sun exposure-related factors. We found no overall association with ever having a live birth (pooled odds ratio (pOR) 0.95, 95% confidence interval (CI) 0.67-1.35). However, we detected a reduced risk of melanoma among women with higher parity (> or = 5 versus no live births pOR 0.76, 95% CI 0.49-1.18, each live birth pOR 0.95, 95% CI 0.91-0.99, p trend = 0.05). Women with both earlier age at first birth (e.g., <20 years) and higher parity (e.g., > or = 5 live births) had a particularly lower risk than women with later age at first birth (e.g., > or = 25 years) and lower parity (e.g., <5 live births) (pOR 0.33, 95% CI 0.14-0.75). The results are compatible with an effect of reproductive history-related factors on melanoma risk, but also could reflect differences in other factors, such as sun exposure history.

Adult↗
PubMed2006

Clinical stage of breast cancer by parity, age at birth, and time since birth: a progressive effect of pregnancy hormones?

Breast cancer diagnosed during pregnancy or 1 to 2 years after birth often occurs at a late stage. Little is known about tumor characteristics in the high-risk period shortly after a childbirth. We here explore whether stage of disease differs according to timing of births. Results are based on 22,351 Norwegian breast cancer patients of parity 0 to 5, ages 20 to 74 years. The proportion of stage II to IV tumors was considerably higher among parous than nulliparous women at age <30 years (52.7% versus 36.8%, P=0.009), but similar or lower in other age groups (P(interaction)=0.029). In general, the largest proportion of stage II to IV tumors was found among women diagnosed during pregnancy or <2 years after birth. However, among women with late-age births (first or second birth >or=30 years, third birth >or=35 years), as well as women with an early second birth (<25 years), the proportion with advanced disease was rather similar or even higher among those diagnosed 2 to 6 years after birth (49.3-56.0%). The association between clinical stage and time since birth reached statistical significance among women with a late first or second birth and among all triparous women (P <or= 0.032). The subgroups with a high proportion of advanced disease 2 to 6 years after birth corresponded quite well to those previously found to have the most pronounced transient increase in risk after birth. Thus, pregnancy hormones may have a progressive effect on breast cancer tumors in addition to a possible promoting effect. A potential effect of prolactin is discussed.

Adolescent↗
PubMed1997

Adjusting cesarean delivery rates for case mix.

OBJECTIVES: (1) To describe the issues in developing a clinical predictor of cesarean delivery that could be used to adjust reported cesarean rates for case mix, and (2) to compare its performance to other, simpler predictors using clinical and statistical criteria. DATA SOURCES: Singleton births greater than 2,500 grams in Washington State in 1989 and 1990 for whom mothers and infant hospital discharge records could be matched to birth certificate data. DESIGN: Statistical analysis of retrospective merged hospital and birth certificate data, which were used to develop variables and models to predict the probability that any particular delivery would be a cesarean. PRINCIPAL FINDINGS: Merged data led to better predictor variables than those based on one source. A simple four-category hierarchical classification into births with prior cesarean, breech but no prior cesarean, first birth, and other explains 30 percent of the variance in individual cesarean rates. The full clinical model fit the data well and explained 37 percent of the variance. Multiparas without serious complications comprised 35 percent of the mothers and averaged less than 2 percent cesareans. A hospital's predicted cesarean rate depends strongly on the proportion of its births that are first births. CONCLUSION: Government and private agencies have reported cesarean rates as measures of hospital performance. Depending on data and resources available, both simple and complex measures of case mix can be used to adjust reported rates. These adjustments should not include all variables related to the rates. Proper adjustments may not alter hospital rankings greatly, but they will improve the validity and acceptability of the reports.

Birth Certificates↗
PubMed2005

Differences in breast cancer risk factors by tumor marker subtypes among premenopausal Vietnamese and Chinese women.

We evaluated associations between reproductive and lifestyle risk factors with breast cancer tumor marker status in a case-control study. Cases were premenopausal women living in Vietnam and China who were eligible for a clinical trial of oophorectomy and tamoxifen as treatment for breast cancer (n = 682). Controls were nonrelative hospital visitors, matched on age to the cases (n = 649). Immunohistochemical analysis was used to identify the presence of estrogen receptor (ER) and progesterone receptor and the overexpression of HER-2/neu oncogene. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using unconditional logistic regression, adjusted for known confounders. Overall, 280 (61%) tumor samples were ER positive and 176 (38%) were ER negative. HER-2/neu overexpression was detected in 161 (35%) samples, whereas 286 (26%) samples were HER-2/neu negative. We observed an inverse trend between increasing parity and decreasing breast cancer risk (P = 0.002). Women ages > or =25 years at first birth had increased breast cancer risk compared with women ages <25 years at first birth (OR, 1.53; 95% CI, 1.20-1.95). Women who consumed alcohol had increased risk of breast cancer compared with women who did not (OR,1.85; 95% CI, 1.32-2.61). Compared with controls, OR estimates for breast cancer by parity and age at first birth were significantly associated with ER and/or HER-2/neu tumor status by Wald test (P < 0.05). Family history, age at menarche, cumulative lactation, body mass index, and education were not significantly related to breast cancer risk. Our findings support the hypothesis that some breast cancer risk factors differ by ER and HER-2/neu tumor marker subtypes.

Adult↗