Age at menarche and subsequent reproductive events

Menarche and Time to Cycle Regularity Among Individuals Born Between 1950 and 2005 in the US

Importance

Early menarche is associated with adverse health outcomes. Trends toward earlier menarche have been observed in the US, but data remain limited on differences by sociodemographic factors and body mass index (BMI). Time from menarche to cycle regularity is another understudied early-life characteristic with health implications.

Objectives

To evaluate the temporal trends and disparities in menarche and time to regularity and explore early-life BMI as a mediator.

Design, Setting, and Participants

This ongoing cohort study enrolled participants from an ongoing mobile application-based US cohort from November 14, 2019, to March 20, 2023.

Exposures

Birth year (categorized as 1950-1969, 1970-1979, 1980-1989, 1990-1999, and 2000-2005).

Main Outcomes and Measures

Main outcomes were age at menarche and time to regularity, which were self-recalled at enrollment. In addition, early (aged <11 years), very early (aged <9 years), and late (aged ≥16 years) age at menarche was assessed.

Results

Among the 71 341 female individuals who were analyzed (mean [SD] age at menarche, 12.2 [1.6] years; 2228 [3.1%] Asian, 3665 [5.1%] non-Hispanic Black, 4918 [6.9%] Hispanic, 49 518 [69.4%] non-Hispanic White, and 8461 [11.9%] other or multiple races or ethnicities), 5223 were born in 1950 to 1969, 12 226 in 1970 to 1979, 22 086 in 1980 to 1989, 23 894 in 1990 to 1999, and 7912 in 2000 to 2005. The mean (SD) age at menarche decreased from 12.5 (1.6) years in 1950 to 1969 to 11.9 (1.5) years in 2000 to 2005. The number of individuals experiencing early menarche increased from 449 (8.6%) to 1223 (15.5%), the number of individuals experiencing very early menarche increased from 31 (0.6%) to 110 (1.4%), and the number of individuals experiencing late menarche decreased from 286 (5.5%) to 137 (1.7%). For 61 932 participants with reported time to regularity, the number reaching regularity within 2 years decreased from 3463 (76.3%) to 4075 (56.0%), and the number not yet in regular cycles increased from 153 (3.4%) to 1375 (18.9%). The magnitude of the trend toward earlier menarche was greater among participants who self-identified as Asian, non-Hispanic Black, or other or multiple races (vs non-Hispanic White) (P = .003 for interaction) and among participants self-rated with low (vs high) socioeconomic status (P < .001 for interaction). Within a subset of 9865 participants with data on BMI at menarche, exploratory mediation analysis estimated that 46% (95% CI, 35%-61%) of the temporal trend in age at menarche was explained by BMI.

Conclusions and Relevance

In this cohort study of 71 341 individuals in the US, as birth year increased, mean age at menarche decreased and time to regularity increased. The trends were stronger among racial and ethnic minority groups and individuals of low self-rated socioeconomic status. These trends may contribute to the increase in adverse health outcomes and disparities in the US.

Causal associations between female reproductive behaviors and psychiatric disorders: a lifecourse Mendelian randomization study

BACKGROUND

The timings of reproductive life events have been examined to be associated with various psychiatric disorders. However, studies have not considered the causal pathways from reproductive behaviors to different psychiatric disorders. This study aimed to investigate the nature of the relationships between five reproductive behaviors and twelve psychiatric disorders.

METHODS

Firstly, we calculated genetic correlations between reproductive factors and psychiatric disorders. Then two-sample Mendelian randomization (MR) was conducted to estimate the causal associations among five reproductive behaviors, and these reproductive behaviors on twelve psychiatric disorders, using genome-wide association study (GWAS) summary data from genetic consortia. Multivariable MR was then applied to evaluate the direct effect of reproductive behaviors on these psychiatric disorders whilst accounting for other reproductive factors at different life periods.

RESULTS

Univariable MR analyses provide evidence that age at menarche, age at first sexual intercourse and age at first birth have effects on one (depression), seven (anxiety disorder, ADHD, bipolar disorder, bipolar disorder II, depression, PTSD and schizophrenia) and three psychiatric disorders (ADHD, depression and PTSD) (based on p<7.14×10-4), respectively. However, after performing multivariable MR, only age at first sexual intercourse has direct effects on five psychiatric disorders (Depression, Attention deficit or hyperactivity disorder, Bipolar disorder, Posttraumatic stress disorder and schizophrenia) when accounting for other reproductive behaviors with significant effects in univariable analyses.

CONCLUSION

Our findings suggest that reproductive behaviors predominantly exert their detrimental effects on psychiatric disorders and age at first sexual intercourse has direct effects on psychiatric disorders.

From the Ground Up: A Multidisciplinary Approach to Past Fertility and Population Narratives

Population dynamics form a crucial component of human narratives in the past. Population responses and adaptations not only tell us about the human past but also offer insights into the present and future. Though an area of substantial interest, it is also one of often limited evidence. As such, traditional techniques from demography and anthropology must be adapted considerably to accommodate the available archaeological and ethnohistoric data and an appropriate inferential framework must be applied. In this article, I propose a ground-up, multidisciplinary approach to the study of past population dynamics. Specifically, I develop an empirically informed path diagram based on modern fertility interactions and sources of past environmental, sociocultural, and biological evidence to guide high-resolution case studies. The proposed approach is dynamic and can evolve in response to data inputs as case studies are undertaken. In application, this approach will create new knowledge of past population processes which can greatly enhance our presently limited knowledge of high-frequency, small-scale demographic fluctuations, as well as contribute to our broader understanding of significant population disturbances and change throughout human history.

The association between maternal stature and adverse birth outcomes and the modifying effect of race and ethnicity: a population-based retrospective cohort study

BACKGROUND

There are known differences in the risk of perinatal and maternal birth outcomes because of maternal factors, such as body mass index and maternal race. However, the association of maternal height with adverse birth outcomes and the potential differences in this relationship by race and ethnicity have been understudied.

OBJECTIVE

This study aimed to examine the association between maternal stature and adverse perinatal outcomes and the potential modification of the association by race and ethnicity.

STUDY DESIGN

This retrospective cohort study was conducted using data on all singleton births in the United States in 2016 and 2017 (N=7,361,713) obtained from the National Center for Health Statistics. Short and tall stature were defined as <10th and >90th percentiles of the maternal height distribution (<154.9 and >172.7 cm, respectively). Race and ethnicity categories included non-Hispanic White, non-Hispanic Black, American Indian or Alaskan Native Asian or Pacific Islander, and Hispanic. The primary outcomes were preterm birth (<37 weeks of gestation), perinatal death, and composite perinatal death or severe neonatal morbidity. Logistic regression was used to obtain adjusted odds ratios and 95% confidence intervals with adjustment for confounding by maternal age, body mass index, and other factors. Multiplicative and additive effect modifications by race and ethnicity were assessed.

RESULTS

The study population included 7,361,713 women with a singleton stillbirth or live birth. Short women had an increased risk of adverse outcomes, whereas tall women had a decreased risk relative to average-stature women. Short women had an increased risk of perinatal death and composite perinatal death or severe neonatal morbidity (adjusted odds ratios, 1.14 [95% confidence interval, 1.10-1.17] and 1.21 [95% confidence interval, 1.19-1.23], respectively). The association between short stature and perinatal death was attenuated in non-Hispanic Black women compared with non-Hispanic White women (adjusted odds ratio, 1.10 [95% confidence interval, 1.03-1.17] vs 1.26 [95% confidence interval, 1.19-1.33]). Compared with average-stature women, tall non-Hispanic White women had lower rates of preterm birth, perinatal death, and composite perinatal death or severe neonatal morbidity (adjusted odds ratios, 0.82 [95% confidence interval, 0.81-0.83], 0.95 [95% confidence interval, 0.91-1.00], and 0.90 [95% confidence interval, 0.88-0.93], respectively). The association between tall and average stature with perinatal death was reversed in Hispanic women (adjusted odds ratio, 1.27; 95% confidence interval, 1.12-1.44). Compared with average-stature women, all tall women had lower rates of preterm birth, particularly among non-Hispanic Black and Hispanic women.

CONCLUSION

Relative to average-stature women, short women have an increased risk of adverse perinatal outcomes across all race and ethnicity groups; these associations were attenuated in Hispanic women and for some adverse outcomes in non-Hispanic Black and Asian women. Tall mothers have a lower risk of preterm birth in all racial and ethnic groups, whereas tall non-Hispanic White mothers have a lower risk of perinatal death or severe neonatal morbidity compared with average-stature women.

The relationships between women's reproductive factors: a Mendelian randomisation analysis

BACKGROUND

Women's reproductive factors include their age at menarche and menopause, the age at which they start and stop having children and the number of children they have. Studies that have linked these factors with disease risk have largely investigated individual reproductive factors and have not considered the genetic correlation and total interplay that may occur between them. This study aimed to investigate the nature of the relationships between eight female reproductive factors.

METHODS

We used data from the UK Biobank and genetic consortia with data available for the following reproductive factors: age at menarche, age at menopause, age at first birth, age at last birth, number of births, being parous, age first had sexual intercourse and lifetime number of sexual partners. Linkage disequilibrium score regression (LDSC) was performed to investigate the genetic correlation between reproductive factors. We then applied Mendelian randomisation (MR) methods to estimate the causal relationships between these factors. Sensitivity analyses were used to investigate directionality of the effects, test for evidence of pleiotropy and account for sample overlap.

RESULTS

LDSC indicated that most reproductive factors are genetically correlated (rg range: |0.06-0.94|), though there was little evidence for genetic correlations between lifetime number of sexual partners and age at last birth, number of births and ever being parous (rg < 0.01). MR revealed potential causal relationships between many reproductive factors, including later age at menarche (1 SD increase) leading to a later age at first sexual intercourse (beta (B) = 0.09 SD, 95% confidence intervals (CI) = 0.06,0.11), age at first birth (B = 0.07 SD, CI = 0.04,0.10), age at last birth (B = 0.06 SD, CI = 0.04,0.09) and age at menopause (B = 0.06 SD, CI = 0.03,0.10). Later age at first birth was found to lead to a later age at menopause (B = 0.21 SD, CI = 0.13,0.29), age at last birth (B = 0.72 SD, CI = 0.67, 0.77) and a lower number of births (B = -0.38 SD, CI = -0.44, -0.32).

CONCLUSION

This study presents evidence that women's reproductive factors are genetically correlated and causally related. Future studies examining the health sequelae of reproductive factors should consider a woman's entire reproductive history, including the causal interplay between reproductive factors.

Offspring Production Among the Relatives of Istmo Zapotec Men and Muxes

Male androphilia (i.e., sexual attraction toward adult males) is influenced by biological factors, reliably occurs across diverse cultures, and has persisted over evolutionary time despite the fact that it reduces reproduction. One possible solution to this evolutionary paradox is the sexually antagonistic gene hypothesis (SAGH), which states that genes associated with male androphilia reduce reproduction when present in males but increase reproduction when present in their female relatives. The present study tested the SAGH among the Istmo Zapotec-a non-Euro-American culture in Oaxaca, Mexico, where transgender and cisgender androphilic males are known as muxe gunaa and muxe nguiiu, respectively. To test the SAGH, we compared offspring production by the biological relatives of muxe gunaa (n = 115), muxe nguiiu (n = 112), and gynephilic men (i.e., cisgender males who are sexually attracted to adult females; n = 171). The mothers and paternal aunts of muxe gunaa had higher offspring production than those of muxe nguiiu. Additionally, the relatives of muxe gunaa had more offspring than those of gynephilic men, whereas no such differences were found between the families of gynephilic men and muxe nguiiu. Elevated reproduction by the mothers and, particularly the aunts, of muxe gunaa is consistent with the SAGH. However, the absence of group differences between gynephilic men and muxe nguiiu, and the group differences between the two types of muxes are not predicted by the SAGH. This is the first study to demonstrate reproductive differences between kin of transgender and cisgender androphilic males within the same non-Euro-American culture.

Is menarche occuring earlier among Lebanese girls?

BACKGROUND

Early menarche is associated with increased risks for several diseases such as cardiovascular diseases and breast cancer. This analysis aimed at generating evidence on a historical trend towards younger age at menarche among Lebanese girls.

METHODS

A secondary analysis was conducted on data consolidated from three serial cross-sectional national surveys of women in Lebanon (2007, 2009 and 2012). A total of 6150 women were included in order to study the association between date of birth intervals and age at menarche.

RESULTS

The mean age at menarche was 13.06 years, with a peak of the distribution at age 12. Women born before 1950 had a significantly higher mean age at menarche (13.21) compared to those born in 1970 and thereafter (12.95). A stratified analysis showed that women living outside the metropolitan Greater Beirut (GB) area were characterized by an older mean age at menarche (13.11) in all date of birth intervals compared to those in GB (12.89). However, age at menarche declined more significantly over the last two decades among women outside GB, compared to those living in GB.

CONCLUSIONS

Epidemiological figures emerging from this study confirm that trends in Lebanon are in line with a global pattern of decreasing age at menarche. Urban-rural differences suggest that higher caloric content of diet and consequent early overweight, more evident in urban areas, are likely determinants of younger menarche. Evidence from this study calls for an urgent implementation of comprehensive multisectoral obesity prevention in children in Lebanon.

Is the timing of menarche correlated with mortality and fertility rates?

Timing of menarche has largely been studied in the context of a secular trend. However, since mortality and fertility rates are fundamental demographic factors linked to a population’s developmental and reproductive characteristics, we expect that the timing of menarche, a precondition to reproduction, is also associated with these vital rates. We conduct an analysis of 89 countries and 21 demographic, socioeconomic, nutritional, and educational variables selected for their known influence on menarche. Model results predict that a country’s fertility and adult female mortality rates are significant predictors of mean age at menarche, while other covariates are not. Specifically, menarche is delayed in countries with high mortality and high fertility, which may be proxies for assessing overall environmental quality. We emphasize that, for a comprehensive understanding of the timing of menarche, it is critical to take into account both individual- and population-level influences.

Father Absence and Accelerated Reproductive Development in Non-Hispanic White Women in the United States

Girls who experience father absence in childhood also experience accelerated reproductive development in comparison with peers with present fathers. One hypothesis advanced to explain this empirical pattern is genetic confounding, wherein gene-environment correlation (rGE) causes a spurious relationship between father absence and reproductive timing. We test this hypothesis by constructing polygenic scores for age at menarche and first birth using recently available genome-wide association study results and molecular genetic data on a sample of non-Hispanic white females from the National Longitudinal Study of Adolescent to Adult Health. We find that young women's accelerated menarche polygenic scores are unrelated to their exposure to father absence. In contrast, polygenic scores for earlier age at first birth tend to be higher in young women raised in homes with absent fathers. Nevertheless, father absence and the polygenic scores independently and additively predict reproductive timing. We find no evidence in support of the rGE hypothesis for accelerated menarche and only limited evidence in support of the rGE hypothesis for earlier age at first birth.

Age at menarche and prevalence of preterm birth: Results from the Healthy Baby Cohort study

Little is known about the impact of age at menarche on preterm birth. The aim of this study was to examine the association between age at menarche and preterm birth. A total of 11,016 Chinese women who gave birth to live singleton infants were recruited from the Healthy Baby Cohort between 2012 and 2014 in the province of Hubei, China. Age at menarche was reported via face-to-face interviews and was categorized into five groups (≤11, 12, 13, 14 and ≥15 years). Gestational age was estimated using maternal last menstrual period. Preterm birth was defined as delivering a live singleton infant at <37 weeks' gestational age. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Earlier menarche (≤11 years) was associated with an increased prevalence of preterm birth (OR: 1.67, 95% CI: 1.18, 2.36) compared with menarche age at 13 years after controlling for the potential confounders. The findings of our study suggested that a history of earlier menarche might be useful for identifying women at higher risk of preterm birth.

Adolescent Pregnancy

Adolescent pregnancy, although on the decline, represents a significant public health concern. Often adolescents present late to prenatal care, either from lack of knowledge, fear of consequences, limited access, stigma, or all of the above. Although multifaceted, there are many risks both to mother and child that are increased in adolescent pregnancy. Many are unintended and are at risk for repeat adolescent pregnancy, especially within the first 2 years. Risks include but are not limited to: low birth weight, preterm delivery, stillbirth, and preeclampsia, as well as feelings of social isolation, delayed or neglected educational goals, and maternal depression.

Parity, Age at First Birth, and Risk of Death from Bladder Cancer: A Population-Based Cohort Study in Taiwan

The evidence is limited on the relationship between reproductive factors and bladder cancer (BC). We studied 1,292,462 women who had a first and singleton delivery between 1 January 1978 and 31 December 1987. Each woman in the study cohort was tracked from their first childbirth to 31 December 2009. Vital status of the women was determined by crosswalking records with a computerized mortality database. We used Cox proportional hazard regression models to estimate the hazard ratios (HRs) of death from BC associated with maternal age at first birth and parity. The data showed 63 BC deaths during 34,980,246 person-years of follow-up. BC mortality rate was 0.90 cases for every 100,000 person-years. Compared with women who gave birth under the age of 23, the adjusted HR was 1.24 (95% confidence interval (CI) = 0.66–2.35) for women who gave birth between age 23 and 26 and 2.30 (95% CI = 1.21–4.39) for women who gave birth over the age of 26. Increasing age at first birth (p for trend = 0.01) is associated with a trend in increasing risk of BC mortality. Relative to women who had a single childbirth, the adjusted HRs were 1.17 (95% CI = 0.51–2.69) for women who gave birth to two children, and 1.31 (95% CI = 0.56–3.10) for women with three or more childbirths, respectively. These results were not statistically significant. Study results suggests that giving birth at an early age may confer a protective effect on the risk of death from BC.

Parity, Age at First Birth, and Risk of Death from Non-Hodgkin's Lymphoma: A Population-Based Cohort Study in Taiwan

We undertook this study to examine whether there exists an association between parity and age at first birth and risk of death from non-Hodgkin’s lymphoma (NHL). Our sample included a total of 1,292,462 women who had a first and singleton childbirth between 1 January 1978 and 31 December 1987. We followed each subject from their first childbirth to 31 December 2009, and determined their vital status by merging natality data with Taiwan’s national death certificate database. Hazard ratios (HR) of death from NHL associated with parity and age at first birth were estimated using Cox proportional hazard regression models. In all, 412 NHL deaths were recorded during 34,980,246 person-years of follow-up. NHL mortality rate was 1.18 cases per 100,000 person-years. Older age at first birth (>23 vs. ≤23 years) was linked to an increased risk of death from NHL (adjusted HR = 1.41; 95% CI = 1.13–1.75). Controlling for age at first birth, the adjusted HR were 0.74 (95% CI = 0.55–0.98) for women with 2 births, and 0.71 (95% CI = 0.53–0.95) for women with 3 births or more, respectively, when compared with women with only 1 birth. A statistically significant downward trend in the adjusted HR for NHL death was detected with increasing parity (p for trend = 0.05). The HR of death from NHL was decreased by 7% (HR = 0.93; 95% CI = 0.87–0.99) for each additional parity. Our findings are consistent with reproductive factors (parity and early age at first birth) conferring a protective effect against the risk of NHL death.

Age at menarche in a group of French schoolgirls

BACKGROUND

Mean age at menarche in France decreased from 12.78 years in 1979 to 12.6 years in 1994. The aim of this study was to determine mean age at first menstruation in French adolescent girls in order to study the secular trend.

METHODS

Age at first menstruation was noted to the nearest month during recording of anthropometric measurements in three secondary schools in the Aisne administrative department, France, in classes in years 7, 8, 9 and 10. A total of 339 girls aged 11-15 ½ years were examined. The majority were from a social background of workers, employees and middle managerial staff. Mean age at first menses and standard deviation were calculated using the probits method.

RESULTS

Mean age was 12.5 ± 0.08 years (χ(2) γ=14 = 16.7, P > 0.05), indicating that it had remained stable for more than 15 years.

CONCLUSIONS

A secular decline has already been observed in Belgium, Britain, Hungary, Scandinavia and the USA. In all these countries, age at menarche has reached a stable level at around 13 ± 0.5 years.

Parity, age at first birth, and risk of death from asthma: evidence from a cohort in taiwan

This study was undertaken to examine whether there is an association between age at first birth and parity and risk of asthma death. The study cohort consisted of 1,292,462 women in Taiwan who had a first live birth between 1 January 1978 and 31 December 1987. We tracked each woman from the date of their first childbirth to 31 December 2009, and their vital status was ascertained by linking records with the computerized mortality database. Cox proportional hazard regression models were used to estimate hazard ratios of death from asthma associated with parity and age at first birth. A trend of increasing risk of asthma death was seen with increasing age at first birth. The adjusted hazard ratio was 0.75 (95% confidence interval (CI) = 0.53–1.08) among women with two live births and 0.53 (95% CI = 0.36–0.78) among those with three or more births, compared with women who had one live birth. There was a significant decreasing trend in adjusted hazard ratios of asthma death with increasing parity. This study is the first to provide evidences to support an association between reproductive factors (parity and early age at first birth) and the risk of asthma death.

Age at menarche and pregnancy-related pelvic pain

AIM

Menarcheal age is a predictor of several complications related to pregnancy and diseases later in life. We aimed to study if menarcheal age is a risk factor for pregnancy-related pelvic pain.

MATERIAL AND METHODS

A nested case-control study was conducted within the Danish National Birth Cohort, a cohort of pregnant women, recruited during 1996-2002, and their children. In the second trimester of pregnancy the women provided information about age at menarche and potential confounders. Selection of cases (n = 2227) was based on self-reported pelvic pain during pregnancy from an interview done 6 months post-partum. The controls (n = 2588) were randomly selected among women who did not report pelvic pain. We used logistic regression analysis to calculate odds ratios (OR) for pregnancy-related pelvic pain according to age at menarche.

RESULTS

In the cohort, 18.5% of all pregnant women reported pregnancy-related pelvic pain. Compared to women who were 12-14 years old at menarche, the adjusted OR for overall pelvic pain were 1.4 (95% confidence interval [CI] 1.1-1.7) in women 11 years or younger and 0.8 (95%CI 0.6-0.9) in women 15 years or older. The corresponding adjusted OR for severe pelvic pain were 1.6 (95%CI 1.3-2.0) and 0.7 (95%CI 0.6-0.9). When age was analyzed as a continuous variable, the odds for overall and severe pelvic pain decreased with 14% and 16%, respectively, for each increasing year.

CONCLUSIONS

The risk of pregnancy-related pelvic pain decreased with increasing menarcheal age in an 'exposure-response' pattern. A low menarcheal age is a risk indicator and may be a risk factor for pregnancy-related pelvic pain.

Parity, age at first birth, and risk of death from brain cancer: a population-based cohort study in Taiwan

Background

This study was undertaken to examine whether there is an association between parity and age at first birth and risk of death from brain cancer.

Methods

The study cohort consisted of 1,292,462 women who had a first and singleton childbirth between Jan. 1, 1978 and Dec. 31, 1987. We tracked each woman from the time of their first childbirth to December 31, 2009, and their vital status was ascertained by linking records with the computerized mortality database. Cox proportional hazard regression models were used to estimate the hazard ratios (HR) of death from brain cancer associated with parity and age at first birth.

Results

There were 316 brain cancer deaths during 34,980,246 person-years of follow-up. The mortality rate of brain cancer was 0.90 cases per 100,000 person-years. The adjusted HR was 1.35 (95% CI= 0.91-2.01) for women who gave birth between 21 and 25, 1.61 (95% CI=1.05-2.45) for women who gave birth after 25 years of age, respectively, when compared with women who gave birth less than 20 years. A trend of increasing risk of brain cancer was seen with increasing age at first birth. The adjusted HR were 0.73 (95% CI= 0.53-0.99) for women who had 2 children, and 0.60 (95% CI =0.43-0.83) for women with 3 or more births, respectively, when compared with women who had given birth to only 1 child. There was a significant decreasing trend in the HRs of brain cancer with increasing parity.

Conclusions

This study provides evidence that reproductive factors (parity and early age at first birth) may confer a protective effect on the risk of death from brain cancer.

Maternal smoking during pregnancy and reproductive health of daughters: a follow-up study spanning two decades

STUDY QUESTION

Does in utero exposure to constituents of cigarette smoke have a programming effect on daughters' age of menarche and markers of long-term reproductive health?

SUMMARY ANSWER

In utero exposure to constituents of cigarette smoke was associated with earlier age of menarche and--to a lesser extent--changes in the testosterone profile of the young women.

WHAT IS KNOWN ALREADY

Studies observe potential effects of in utero exposure to constituents of cigarette smoke on the intrauterine formation of female gonads, but the consequences on long-term reproductive health in daughters remain unclear.

STUDY DESIGN, SIZE AND DURATION

A prospective cohort study was designed using data from 965 pregnant women enrolled prior to a routine 30th-week antenatal examination at a midwifery practice in Denmark from 1988 to 1989 and a follow-up of their 19-21-year-old daughters in 2008.

PARTICIPANTS/MATERIALS, SETTING AND METHODS

The pregnant women provided information on lifestyle factors during pregnancy, including the exact number of cigarettes smoked per day during the first and the second trimesters. A total of 438 eligible daughters were asked to complete a web-based questionnaire on reproductive health and subsequently invited to participate in a clinical examination during 2008. Of the 367 daughters (84%) who answered the questionnaire, 267 (61%) agreed to further examination. Information on menstrual pattern was provided at examination, blood samples were drawn to be analyzed for serum levels of reproductive hormones [FSH, LH, estradiol (E(2)), sex hormone-binding globulin, anti-Müllerian hormone, dehydroepiandrosterone-sulphate (DHEAS), free testosterone and free E(2)] and number of follicles (2-9 mm) were examined by transvaginal ultrasound. The daughters were divided into three exposure groups according to the level of maternal smoking during first trimester [non-exposed (reference), low-exposed (mother smoking >0-9 cigarettes/day) and high-exposed (mother smoking ≥ 10 cigarettes/day)]. Data were analyzed by multiple regression analyses in which we adjusted for potential confounders. Both crude and adjusted test for trend were carried out using maternal smoking during the first trimester as a continuous variable.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed an inverse association between in utero exposure to constituents of cigarette smoke and age of menarche (P = 0.001). Daughters exposed to >0-9 cigarettes/day debuted with -2.7 [95% confidence interval (CI) -5.2 to -0.1] percentage earlier age of menarche, whereas daughters exposed to ≥ 10 cigarettes/day had -4.1 (95% CI: -6.6 to -1.5) percentage earlier age of menarche corresponding to 6.5 (95% CI: -10.7 to -2.2) months. There was a non-significant tendency towards lower levels of testosterone and DHEAS with increasing in utero exposure to constituents of cigarette smoke but no associations with follicle number, cycle length or serum levels of the other reproductive hormones were observed.

LIMITATIONS AND REASONS FOR CAUTION

We collected information on age of menarche retrospectively but the recall time was relatively short (2-10 years) and the reported values were within the normal range of Caucasians. Analyses of reproductive hormones are presented only for the group of daughters who were non-users of hormonal contraceptives because users were excluded, leaving only a low number of daughters available for the analyses (n = 75), as reflected in the wide CIs. The analyses of hormones were further adjusted for menstrual phase at time of clinical examination (follicular, ovulation and luteal phase) because blood samples were not collected on a specific day of the menstrual cycle.

WIDER IMPLICATIONS OF THE FINDINGS

This study supports the limited evidence of an inverse association between maternal smoking during pregnancy and age of menarche and further addresses to what extent reproductive capacity and hormones may be programmed by maternal smoking during pregnancy. A trend toward earlier maturation of females is suggested to have implications on long-term reproductive function.

STUDY FUNDING/COMPETING INTEREST(S)

Supported by a scholarship from The Lundbeck Foundation (R93-A8476). No conflict of interest declared.

Higher parity and earlier age at first birth are associated with lower risk of death from colon cancer

This study was undertaken to examine whether there is an association between parity and age at first birth and risk of colon cancer. The study cohort consisted of 1,292,462 women who had a first and singleton childbirth between 1978 and 1987. We tracked each woman from the time of their first childbirth to December 31, 2009, and their vital status was ascertained by linking records with the computerized mortality database. We used the Cox proportional hazards model with time-dependent covariates to estimate the hazard ratios (HR) of death from colon cancer associated with parity and age at first birth. We limited eligible colon cancer deaths to those who were 45 years old or more to exclude possible heredity colon cancer cases, which usually occur at an early age. There were 670 colon cancer deaths during 34,980,246 person-years of follow-up. The colon cancer death rate was 1.96 cases per 100,000 person-years. The adjusted HR was 2.76 (95% CI = 1.60-4.75) for women who gave birth between 20 and 24 years and 7.35 (95% CI = 4.28-12.62) for women who gave birth after 24 years of age when compared with women who gave birth at younger than 20 years. A rising risk of colon cancer was seen with increasing age at first birth. The adjusted HR were 0.81 (95% CI = 0.65-1.02) among women with two live births, 0.93 (95% CI = 0.74-1.18) among women with three live births and 0.72 (95% CI = 0.51-1.00) for women with four or more births when compared with women who had given birth to only one child. The present study provides evidence that reproductive factors (parity and early age at first birth) may confer a protective effect on the risk of colon cancer.

The relationship between fertility and lifespan in humans

Evolutionary theories of aging predict a trade-off between fertility and lifespan, where increased lifespan comes at the cost of reduced fertility. Support for this prediction has been obtained from various sources. However, which genes underlie this relationship is unknown. To assess it, we first analyzed the association of fertility with age at menarche and menopause, and with mortality in 3,575 married female participants of the Rotterdam Study. In addition, we conducted a candidate gene study where 1,664 single nucleotide polymorphisms (SNPs) in 25 candidate genes were analyzed in relation to number of children as a measure of fertility. SNPs that associated with fertility were analyzed for association with mortality. We observed no associations between fertility and age at menarche (p = 0.38) and menopause (p = 0.07). In contrast, fertility was associated with mortality. Women with two to three children had significantly lower mortality (hazard ratio (HR), 0.82; 95% confidence interval (95% CI), 0.69-0.97) compared to women with no children. No such benefit was observed for women with four or more children, who had a similar mortality risk (HR, 0.93; 95% CI, 0.76-1.13) as women with no children. The analysis of candidate genes revealed four genes that influence fertility after correction for multiple testing: CGB/LHB gene cluster (p = 0.0036), FSHR (p = 0.023), FST (p = 0.023), and INHBA (p = 0.021). However, none of the independent SNPs in these genes predicted mortality. In conclusion, women who bear two to three children live longer than those who bear none or many children, but this relationship was not mediated by the candidate genes analyzed in this study.

Parity, age at first birth, and risk of death from liver cancer: Evidence from a cohort in Taiwan

BACKGROUND AND AIM

The present study was undertaken to examine whether there is an association between parity and age at first birth and risk of liver cancer.

METHODS

The study cohort consisted of 1,292,462 women who had a first and singleton childbirth between 1 January 1978 and 31 December 1987. We tracked each woman from the time of their first childbirth to 31 December 2007, and their vital status was ascertained by linking records with the computerized mortality database. Cox proportional hazard regression models were used to estimate the relative risks (RR) of death from liver cancer associated with parity and age at first birth.

RESULTS

There were 826 liver cancer deaths during 32,464,186.58 person-years of follow-up. The mortality rate of liver cancer was 2.54 cases per 100,000 person-years. The adjusted RR was 1.59 (95% confidence interval [CI] = 1.36-1.86) for women who gave birth between 26 and 30, 2.41 (95% CI = 1.81-3.20) for women who gave birth between 31 and 35, and 6.26 (95% CI = 4.27-9.19) for women who gave birth after 35 years of age, respectively, when compared with women who gave birth at less than 25 years of age. The adjusted RR was 0.72 (95% CI = 0.59-0.87) for women who had two to three children, and 0.63 (95% CI = 0.47-0.84) for women with four or more births, respectively, when compared with women who had given birth to only one child.

CONCLUSIONS

The present study suggests that reproductive factors (parity and early age at first birth) may confer a protective effect on the risk of liver cancer.

Teen motherhood in cross-cultural perspective

Teen motherhood is the prevalent childbearing pattern in most traditional populations. Yet early motherhood is associated with negative biological and social outcomes in the developed world. We review the teen pregnancy literature in light of this discrepancy, emphasizing two core debates. The first debate centers on whether teens have poor pregnancy outcomes compared to older women, and whether negative outcomes are biologically based. Second, we consider the debate over the confounding effects of socio-economic conditions associated with being young. When teens are considered as a group, results are inconsistent across studies. When teens are disaggregated by age, the strongest finding across studies is that biological risk is concentrated in only the youngest of mothers. Negative consequences are associated with teen motherhood not because of chronological age per se, but because of relative developmental maturity and the availability of non-maternal support. In most traditional societies as well as in some sectors of developed societies, teen motherhood occurs within the context of extended kin networks and is subsidized through reliable economic and childcare assistance. Child-rearing practices, rather than pregnancy per se, may explain much of the discrepancy in the prevalence, success and attitudes toward teen motherhood in traditional and developed societies.

Outcomes of early pubertal timing in young women: a prospective population-based study

OBJECTIVE

Early pubertal timing in girls is associated with psychosocial problems throughout adolescence, but it is unclear whether these problems persist into young adulthood. The authors analyzed outcomes in adolescence and young adulthood in girls in a longitudinal study.

METHOD

The data for this study were from the prospective population-based Great Smoky Mountains Study (N=1,420), which initially recruited children at ages 9, 11, and 13 and followed them into young adulthood. Pubertal timing was defined on the basis of self-reported Tanner stage and age at menarche. Outcome measures included functioning related to crime, substance use, school/peer problems, family relationships, sexual behavior, and mental health in adolescence (ages 13 to 16) as well as crime, substance use, education/socioeconomic status, sexual behavior, and mental health in young adulthood (ages 19 and 21).

RESULTS

In adolescence, early-maturing girls displayed higher levels of self-reported criminality, substance use problems, social isolation, early sexual behavior, and psychiatric problems. By young adulthood, most of these differences had attenuated. Functioning for early maturers improved in some areas; in others, on-time and late maturers had caught up with their early-maturing peers. Nevertheless, early-maturing girls, particularly those with a history of adolescent conduct disorder, were more likely to be depressed in young adulthood compared to their counterparts. Early maturers were also more likely to have had many sexual partners.

CONCLUSIONS

The effects of early pubertal timing on adolescent psychosocial problems were wide ranging but diminished by young adulthood for all but a small group.

Parity, age at first birth, and risk of death from pancreatic cancer: evidence from a cohort in Taiwan

OBJECTIVES

This study was undertaken to examine whether there is an association between parity and age at first birth and risk of pancreatic cancer.

METHODS

The study cohort consisted of all women with a record of a first and singleton childbirth in the Birth Registration System between 1978 and 1987. We tracked each woman from the time of their first childbirth and linked their vital status with mortality database. Cox proportional hazard regression models were used to estimate the relative risks (RRs) of death from pancreatic cancer associated with parity and age at first birth.

RESULTS

A trend of increasing risk of pancreatic cancer was seen with increasing age at first birth. The adjusted RR was 0.69 (95% confidence interval, 0.49-0.98) for women who born 2 children and 0.64 (95% confidence interval, 0.44-0.93) for women with 3 or more births, respectively, when compared with women who had given birth to only 1 child. There was a significant decreasing trend in the RR of pancreatic cancer with increasing parity.

CONCLUSIONS

This study provides evidence that reproductive factors (parity and early age at first birth) may confer a protective effect on the risk of pancreatic cancer.

Mother's age at menarche and offspring size

Objective

An individual’s growth trajectory is, at least in part, inherited. Mother’s early age at menarche has been associated with taller offspring height and greater body mass index (BMI) at age 9 years, suggesting that mother’s age at menarche may be an intergenerational marker of growth. We examined the association between mother’s age at menarche and childhood size at birth, and at the ages 1, 3, 4, 7, and 8 years in the Collaborative Perinatal Project (CPP).

Subjects

We examined 128,636 measurements from 31,474 Black and White children. We transformed the original measurements into z-scores. Child size was examined in mixed models, adjusted for center, child sex, race, socioeconomic index, child’s exact age at measurement (in months), mother's age at recruitment and, depending on which measure was the outcome in the specific model, mother's height, pre-pregnancy weight, or BMI.

Results

Compared with children whose mother had menarche at age 15 or later, children whose mothers had age at menarche before age 12 were taller from age 1 and had higher BMI at ages 7 and 8 (0.17 and 0.19 z, respecively).

Conclusions

Mother’s age at menarche is a modest predictor of their children’s growth trajectory. The mechanism is likely to be heritable, although other explanations are possible.

Early sexual maturity among Pumé foragers of Venezuela: fitness implications of teen motherhood

Because humans have slow life histories, discussions of the optimal age at first birth have stressed the benefits of delayed reproduction. However, given the diversity of ecological, fertility, and mortality environments in which humans live, reproductive maturity is expected to be highly variable. This article uses reproductive histories to examine a pattern of early menarche and first birth among the Pume, a group of South American foragers. Age at menarche and first birth are constructed using both retrospective and cross-sectional data for females over the age of 10 (n = 83). The objectives are first to define these patterns and then discuss their reproductive consequences. On average, Pume girls reach menarche at age 12.9, and give birth to their first child at age 15.3-15.5 (retrospective and cross-sectional data, respectively). This populational average falls several years prior to what often is considered the human norm. Two questions are then considered. What are the infant mortality costs across a mother's reproductive career? How does surviving fertility vary with age at first birth? Results indicate that the youngest of first-time mothers (<14) are four times more likely to loose their firstborns than older first-time mothers (> or =17). Given parity-specific mortality rates, the optimal strategy to minimize infant mortality and maximize reproductive span is to initiate childbearing in the midteens. Women gain no additional advantage in surviving fertility by delaying childbearing until their late teens.

Risk of spontaneous abortion among women exposed to polybrominated biphenyls

Accidental contamination of livestock in Michigan in 1973 with polybrominated biphenyls (PBBs) led to the establishment of a registry of exposed individuals in 1976. At the time of enrollment, serum was collected and analyzed for PBBs and polychlorinated biphenyls (PCBs). In 1997, women aged 18 years or older and active in the registry were invited to participate in a telephone interview about their health. Using generalized estimating equations to account for correlated outcomes within the same woman, we assessed the risk of spontaneous abortion among 529 women with 1344 potentially exposed pregnancies. PBB and PCB exposure were not associated with risk of spontaneous abortion after adjusting for maternal age at conception, age at menarche, and prior infertility. Compared to pregnancies with PBB exposure below the limit of detection, those with levels above 2.9 ppb had a non-significant reduced odds of spontaneous abortion (adjusted OR=0.73; 95% CI=0.47-1.13). Compared to pregnancies with PCB exposure below the limit of detection, those with levels above 6.5 ppb had little difference in risk (adjusted OR=0.91; 95% CI=0.59-1.41). Maternal age at conception above 34 years was significantly associated with elevated risk of spontaneous abortion (OR=2.46; 95% CI=1.10-5.49). The effect of prior infertility was of borderline significance (OR=1.52; 95% CI=0.98-2.38). Older age at menarche was associated with decreased risk of spontaneous abortion (adjusted OR=0.58; 95% CI: 0.38-0.89, comparing menarche at 12-13 with menarche <12). Our results do not support an association between exposure to PBBs or PCBs and risk of spontaneous abortion.

The influence of age at menarche on the fertility of Chinese women

This paper examines the effect of age at menarche on children ever born (CEB). We use data from the 1997 Sample Survey of Population and Reproductive Health conducted by the China Population Information and Research Center and the State Family Planning Commission. Poisson regression models are estimated for 10,919 ever married Chinese Han women. The influence of a woman's age at menarche on her CEB is examined while controlling for the social effects of rural/urban residency, education, her number of fecund years, whether her first birth occurred before or after the initiation of China's one child policy, and her age at first marriage. The results support our hypothesized positive association between age at menarche and CEB. That is, the later a woman's age at menarche, the greater her number of children ever born. Holding the other five independent variables constant, we show that for every additional month in age at menarche, a Chinese Han woman's mean number of children ever born increases by 0.5 percent. Some of the implications of these results are explored.

Timing of pubertal maturation in girls: an integrated life history approach

Life history theory provides a metatheoretical framework for the study of pubertal timing from an evolutionary-developmental perspective. The current article reviews 5 middle-level theories--energetics theory, stress-suppression theory, psychosocial acceleration theory, paternal investment theory, and child development theory--each of which applies the basic assumptions of life history theory to the question of environmental influences on timing of puberty in girls. These theories converge in their conceptualization of pubertal timing as responsive to ecological conditions but diverge in their conceptualization of (a) the nature, extent, and direction of environmental influences and (b) the effects of pubertal timing on other reproductive variables. Competing hypotheses derived from the 5 perspectives are evaluated. An extension of W. T. Boyce and B. J. Ellis's (in press) theory of stress reactivity is proposed to account for both inhibiting and accelerating effects of psychosocial stress on timing of pubertal development. This review highlights the multiplicity of (often unrecognized) perspectives guiding research, raises challenges to virtually all of these, and presents an alternative framework in an effort to move research forward in this arena of multidisciplinary inquiry.

Age at menarche and the reproductive performance of Saudi women

BACKGROUND

Saudi Arabia has undergone substantial development in the recent past with concomitant changes in living conditions, and economic and general health status that have affected the age at menarche in Saudi women. We evaluated the current age at menarche and reproductive events among Saudi women.

SUBJECTS AND METHODS

Age, age at menarche, age at marriage, age of first pregnancy, number of children, and number of abortions were collected for Saudi women attending King Khalid University Hospital (KKUH) over a 3-month period in 2002.

RESULTS

For 989 Saudi women, the mean age at menarche was 13.05 years. There was a decrease in the age of menarche over the past 20 years, an increase in the age of marriage, age of first pregnancy, and a decrease in the number of children and abortions. Compared with data from two decades, the age at menarche decreased significantly from 13.22 to 13.05 years.

CONCLUSION

The decrease in the age of menarche among Saudi women indicates better socioeconomic status and improvements in health.

The effect of caffeine consumption and nausea on the risk of miscarriage

Evidence for a harmful effect of caffeine intake on risk of miscarriage (spontaneous abortion) is inconsistent and nausea during pregnancy has been claimed to explain any association seen. The objective of this analysis was to determine whether caffeine consumption both before and during pregnancy influenced the risk of miscarriage in a group of pregnant women in the UK. We examined the association with maternal caffeine intake in a case-control study of 474 nulliparous women. Participants were recruited during the years 1987-89 from the Royal Berkshire Hospital in Reading and from a large group practice situated within the hospital's catchment area. Cases were 160 women with a clinically diagnosed miscarriage and controls were 314 pregnant women attending for antenatal care. Information on coffee/tea/cola consumption and potential confounders was collected by interview and caffeine content was assigned to individual drinks according to published data on caffeine content of beverages. Compared with a maternal caffeine intake of < 151 mg/day, we found evidence that caffeine consumption > 300 mg/day doubled the risk of miscarriage. Adjusted odds ratios were 1.94 [95% CI 1.04, 3.63] for 301-500 mg/day and 2.18 [95% CI 1.08, 4.40] for > 500 mg/day. This effect could not be explained by nausea in pregnancy. Nausea appeared to be strongly independently associated with a reduced risk of miscarriage (test for trend P < 0.0001). There was no evidence that prepregnancy caffeine consumption affected the risk. Our results indicate that high caffeine consumption during pregnancy (>300 mg/day), in particular coffee consumption, is an independent risk factor for increased risk and nausea is an independent protective factor for a lower risk of miscarriage.

Menarcheal age and subsequent patterns of family formation

We examine whether age at menarche affects age at first marriage or first birth using two samples of U.S. women. Data are drawn from the Tremin Trust, a longitudinal study of menstrual cycles that recruited white women who were students at the University of Minnesota and from a survey of a nationally representative sample of white women born between 1900 and 1910. Regression models with cubic splines were used to analyze the relationship between age at menarche and age at first marriage. Cox proportional hazard models were used to examine the effect of age at menarche on the interval between marriage and first birth. Unlike earlier work, we found that once secular trends in both age at marriage and age at menarche were taken into account, there was no evidence that age at menarche affects either age at marriage or the timing of first births in these U.S. women.

A cohort study of dietary fibre intake and menarche

OBJECTIVE

To evaluate the influence of dietary fibre on menarche in a cohort of pre-menarcheal girls.

DESIGN

Prospective cohort study.

SETTING

Ontario, Canada.

SUBJECTS

Free-living pre-menarcheal girls (n = 637), 6 to 14 years of age.

METHODOLOGY

Information on dietary intake, physical activity and date of menarche was collected at baseline and was updated annually by self-administered questionnaires for three years. Cox proportional hazards models were used to evaluate the association between dietary fibre and menarche, adjusting for age at entry to the study and potential confounders.

RESULTS

A higher intake of energy-adjusted dietary fibre was associated with a lower risk of (i.e. a later age at) menarche (relative hazard 0.54, 95% confidence interval (CI) 0.31-0.94 for highest vs. lowest quartile, P for trend = 0.027). At the fibre component level, a higher intake of energy-adjusted cellulose was associated with a lower risk of menarche (relative hazard 0.45, 95% CI 0.26-0.76, P for trend = 0.009).

CONCLUSIONS

The findings are consistent with the hypothesis that pre-menarcheal dietary intake can influence menarche.

Association between maternal age at menarche and newborn size

The impact of maternal age at menarche on newborn size was tested using data from 4,996 single births taking place at Vienna, Austria, between 1985 and 1995--so-called teenager pregnancies were excluded from the present analyses. All women experienced pregnancies between the ages of 19 to 42 years. Maturational time was related significantly to infant weight and length independent of maternal age and behavioral variables such as smoking. Early maturation, i.e., age at menarche before the 12th birthday, was significantly associated with decreased newborn weight and size. The incidence of low-weight newborns was significantly higher in early-maturing mothers. The more favorable nutritional status of women whose menarche occurred relatively early was not able to compensate for the negative effects of early maturation on intrauterine growth. Higher circulating estrogen levels in early maturers preserved into adulthood are discussed as possible reasons for intrauterine growth retardation of the offspring of early-maturing mothers.

The missing politics and unsettled science of the trend toward earlier puberty

The age of puberty in many populations has declined steeply over recent centuries and may be declining still. Consequently, today's children tend to experience the hormonal stresses of rapid development at younger ages than did their ancestors, around whose later, if not more gradual, maturation traditional behavioral expectations formed. Little has been made of this "rush to puberty" outside the life sciences. This article reviews its historical documentation, scholarly appreciation, epidemiological correlations, putative physiological and environmental explanations, sociological implications, and largely latent politics.

EVOLUTIONARY ECOLOGY OF HUMAN REPRODUCTION

▪ Abstract  Evolutionary ecology of human reproduction is defined as the application of natural selection theory to the study of human reproductive strategies and decision-making in an ecological context. The basic Darwinian assumption is that humans—like all other organisms—are designed to maximize their inclusive fitness within the ecological constraints to which they are exposed. Life history theory, which identifies trade-off problems in reproductive investment, and evolutionary physiology and psychology, which analyzes the adaptive mechanisms regulating reproduction, are two crucial tools of evolutionary reproductive ecology. Advanced empirical insights have been obtained mainly with respect to the ecology of fecundity, fertility, child-care strategies, and differential parental investment. Much less is known about the ecology of nepotism and the postgenerative life span. The following three theoretical aspects, which are not well understood, belong to the desiderata of future improvement in evolutionary human reproductive ecology: (a) the significance of and the interactions between different levels of adaptability (genetic, ontogenetic, and contextual) for the adaptive solution of reproductive problems; (b) the dialectics of constraints and adaptive choices in reproductive decisions; and (c) the dynamics of demographic change.

Trends in fertility patterns of women in rural Zimbabwe

To study changes over time in reproductive health and living conditions of women in a rural setting in Zimbabwe, 12 villages were selected at random in the Gutu district, Masvingo province. During two study periods in 1992 and 1993, 1,213 women of fertile age (15-44 years) were interviewed and examined. Median age at menarche was 15 years, with a decrease of 0.4 years from the oldest to the youngest age group. There has been no increase in the mean height of women, indicating no change in determinants of nutritional status of girls in childhood and adolescence. Younger women still marry at a median age of 19 years but prefer smaller families. Level of education is the main determinant for age at marriage and preferred family size. A low prevalence of primary (1%) as well as secondary infertility (4%) was found in spite of the currently reported high prevalence of sexually transmitted diseases in Zimbabwe.

Accuracy of short-term recall of age at menarche

This study was conducted as part of the third annual follow-up of a cohort of 657 girls to test the accuracy of short-term recall of age at menarche. During the first and second annual follow-ups of the cohort, 101 girls had reported menarche. We sent questionnaires to these subjects at the third annual follow-up and asked them to recall the month and year of their menarche. Eighty-eight respondents returned their questionnaires with the relevant information. Overall, 59.1% of the respondents were able to recall their menarche with the exact month and year. The mean recall interval was 430 days. When the data were grouped by the interval of recall, higher accuracy was observed with a shorter interval of recall. With a mean interval of recall of 323 days, 66.1% of the subjects were able to recall their menarche correctly, whereas with a mean interval of 649 days, only 44.8% of the subjects were able to recall correctly.

Risk factors for spontaneous abortion among Saudi women

The objective of this study was to identify important risk factors for spontaneous abortion (SA) among Saudi women. It was a case-control study conducted at King Khalid University Hospital, Riyadh, Saudi Arabia. The cases were 226 consecutive women hospitalized for SA between October 1992 and January 1993. The controls were 226 consecutive women who had normal delivery in the same hospital during the same period. Bivariate analysis using chi-square tests and estimates of relative risks indicated a positive association of age at menarche with risk of SA (P < 0.01). Also, there was a significant higher risk of SA when a women was married to a blood related husband than if married to a non relative (RR = 2.1). The number of previous abortions was also positively related to the risk of SA in the current pregnancy (P < 0.01). Compared to primigravidas, the risk of SA was 3.2 times greater than if the outcome of the most recent pregnancy was also an SA. Other factors that had significant bivariate association with SA were a family history of SA, abdominal trauma, and infection during pregnancy. When multiple logistic regression was used to adjust for the effects of confounding variables, all the factors that showed significant bivariate association with SA (except outcome of the last pregnancy) remained significant. Early menarche may be protective, but further study is needed to confirm this. Greater attention should be given to pregnant women who had personal or family history of SA and those who had trauma and/or infection during pregnancy. Premarital counselling concerning consanguineous marriages is recommended.

Nutritional aspects of breast cancer

Nutrition, in its broadest sense, plays a clear role in breast cancer, identified through its relationship to such known risk factors as rate of growth and development, age at menarche, adult height, postmenopausal body weight, and fat distribution. The relative importance of daily diet is hotly debated. There is no agreement on the relative importance of nutrition's effect, the responsible food groups and nutrients, nor the age or ages at which it can be influential. Evidence linking breast cancer and diet comes from human ecologic and observational studies as well as a body of experimental feeding studies in rats and mice. The population studies, including increasing numbers of migrant studies, and the animal experiments suggest that high-fat diets promote breast cancer, particularly among older women. Studies that compare diets of persons with and without breast cancer and those that record breast cancer incidence among women with different dietary histories have been inconclusive enough as to warrant randomized intervention trials. Recognition of differences between the risk factors for premenopausal and postmenopausal women and increasing insight into the ages at which known risk factors exert their influence have helped in the design of these trials. Human feeding studies and the trials themselves are identifying metabolic changes and their biomarkers as well as biomarkers for changes in fat and nutrient intakes. The Women's Health Initiative Dietary Modification Trial was designed to show whether a sustained (9-year) low-fat, high-fruit-and-vegetable eating pattern will lower the incidence of breast cancer among women who will be between ages 59 and 88 when the trial ends, the time of peak incidence. Meanwhile, the Women's Intervention Nutrition Study will learn in approximately 5 years whether a low-fat, adjuvant eating pattern will improve the prognoses of postmenopausal women with early and moderate stage breast cancer and whether tamoxifen should be used as at least part of their treatment. The results of these trials will have important applications for both public health and the provision of medical care.

Sociobiological risk factors for spontaneous abortion in Malaysia

OBJECTIVE

To evaluate the risk factors of spontaneous abortion.

METHODS

A case-control study was conducted by interviewing 350 women who were admitted to the university gynaecological unit for spontaneous abortion and 350 women who delivered normally at the university obstetric unit. Odds ratios, as the estimators of relative risks, were calculated.

RESULTS

The relative risk for spontaneous abortion among women in the age-group 30 to 39 years was 1.61 and among women above 40 years of age was 3.68 when compared to those below 30 years of age. In relation to career women, the relative risk of spontaneous abortion for housewives was 0.45. Ethnic group, parity, subfertility, previous induced abortion, ectopic pregnancy, contraception and menarcheal age did not influence the risk of spontaneous abortion.

CONCLUSION

Increasing age and a woman's career are significant risk factors of spontaneous abortion.

Ever-pregnant and never-pregnant teens in a temporary housing shelter

Adolescent pregnancy and childbearing are of national concern; documented sequelae are numerous and varied. The primary purpose of this cross-sectional study is to describe the differences in selected demographic, sociocultural, physiological, psychological, and cognitive variables among 136 ever-pregnant and never-pregnant teens residing in a temporary housing shelter. Teens who experienced a pregnancy had significantly higher chronological age, gynecological age, and school grade level in addition to reporting significantly greater histories of both rape and voluntary sexual activity than did never-pregnant teens. This study indicates that teen pregnancy is a major problem among adolescents in temporary housing shelters. Our findings provide guidance for clinical interventions and further research with this at-risk population.