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Sex preference and third birth intervals in a traditional Indian society.

The traditional preference for sons may be the main hindrance to India's current population policy of two children per family. In this study, the effects of various sociodemographic covariates, particularly sex preference, on the length of the third birth interval are examined for the scheduled caste population in Assam, India. Life table and hazards regression techniques are applied to retrospective sample data. The analysis shows that couples having two surviving sons are less likely to have a third child than those without a surviving son and those with only one surviving son. Age at first marriage, length of preceding birth intervals, age of mother, and household income have strong effects on the length of the third birth interval.

Adolescent↗

General epidemiology of breast cancer in northern Italy.

The role of the major identified risk factors for breast cancer was assessed using data from a hospital-based case-control study conducted in Northern Italy on 1108 women with histologically confirmed breast cancer and 1281 control subjects with a spectrum of acute conditions unrelated to any of the established or potential risk factors for breast disease. With reference to nulliparous women, the risk of breast cancer was below unity for those who first gave birth below age 25, and above unity for those with later first full-term pregnancy. However, in each stratum of age at first birth, the point estimate was below unity for women with five or more births. The relative risk for greater than or equal to 5 births compared with 1 or 2 was 0.6 (95% confidence interval = 0.4-0.9) when allowance was made for age at first birth. Likewise, there was a significant and independent effect of age at last birth which was evident in various strata of parity and age at first birth. The overall relative risk for last birth at 30 years or over compared with under 30 was 1.4 (95% confidence interval = 1.1-1.8). There was little relation of breast cancer risk with abortions or miscarriages. Breast cancer cases reported earlier menarche and later menopause; further, lifelong irregularities in menstrual pattern were less common among the cases (relative risk = 0.6, 95% confidence interval = 0.5-0.8). The risk estimates were elevated in women with positive history of benign breast disease, family history of breast cancer and greater body mass index.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Induced↗

Short birth intervals: the experience of Bangladeshi immigrants to the United Kingdom, 1974 through 1984.

Linked maternity data were used to calculate birth intervals from records of 7129 consecutive singleton births to Bangladeshi mothers who delivered in the London borough of Tower Hamlets from 1974 through 1984. During this period, there was active migration of women from Bangladesh, the majority coming to the United Kingdom as brides or young wives. Risk of a subsequent birth was calculated using life tables, and results were compared to national data from Bangladesh and the United Kingdom. The risk of a subsequent birth within 12 and 18 months for Bangladeshi women was twice that reported nationally for women in Bangladesh or in the United Kingdom, despite a demonstrable underestimation inherent in the method. The risk of short birth intervals was lower in the first 5 years than in the later years covered by the investigation. Short intervals stress maternal and infant health and are preventable. Possible explanations for the unusual excess of very short birth intervals include: (1) the wide availability of artificial milk in a community that has traditionally used breast-feeding as the main method of spacing pregnancies and (2) confusion regarding appropriate postnatal contraception in a young, healthy married population.

Bangladesh↗

Outcome of pregnancy in homozygous sickle cell disease.

OBJECTIVE: Previous reports on pregnancy in homozygous sickle cell (SS) disease are biased by hospital-based, more severely affected subjects and may have underestimated recurrent early pregnancy losses. We report pregnancy outcome in a representative sample of SS subjects subsequently referred to as "subjects" or "sickle cell subjects," and matched normal controls followed from birth. METHODS: The outcomes of 94 pregnancies in 52 subjects and 157 pregnancies in 68 controls followed in a cohort study from birth are presented. Outcome measures included the age at menarche, interval to first pregnancy, outcome of pregnancy, and maternal complications. Possible predictors of low birth weight are assessed. Outcomes were compared by the Kaplan-Meier analysis for interval to first pregnancy and by Student t test, chi(2) test, or Fisher exact test, as appropriate. Correction was made for multiple testing, and multiple linear regression was used for analysis of birth weight. RESULTS: Compared with controls, SS subjects had later menarche (median age 15.4 versus 13.0 years) and first pregnancy (median age 23.7 versus 20.1 years), and more spontaneous abortions (36% versus 10%). Babies of SS subjects had a lower gestational age (P <.001) and lower birth weight (P <.001), the latter being significantly affected by sickle-related events in pregnancy. There was no difference in pregnancy-induced hypertension, preeclampsia, or antepartum or postpartum hemorrhage, but a retained placenta was marginally more common in SS subjects (Fisher exact test, P =.007 after adjustment for multiple testing). Two SS subjects died, a mortality rate of 2.1%. CONCLUSION: The increased fetal loss and maternal morbidity in mothers with homozygous sickle cell disease is confirmed. LEVEL OF EVIDENCE: II-2

Abortion, Spontaneous↗

Testicular cancer risk and maternal parity: a population-based cohort study.

The aim was to study, in a population-based cohort design, whether first-born sons run a higher risk of testicular cancer than later born sons; to investigate whether this difference in risk was affected by birth cohort, age of the son, maternal age, interval to previous delivery and other reproductive factors; and, finally, to evaluate to what extent changes in women's parity over time might explain the increasing incidence of testicular cancer. By using data from the Civil Registration System, a database was established of all women born in Denmark since 1935 and all their children alive in 1968 or born later. Sons with testicular cancer were identified in the Danish Cancer Registry. Among 1015994 sons followed for 15981 967 person-years, 626 developed testicular cancer (443 non-seminomas, 183 seminomas). Later born sons had a decreased risk of testicular cancer (RR = 0.80, 95% CI = 0.67-0.95) compared with first-born sons. The RR was 0.79 (95% CI = 0.64-0.98) for non-seminomas and 0.81 (95% CI = 0.58-1.13) for seminomas. There was no association between testicular cancer risk and overall parity of the mother, maternal or paternal age at the birth of the son, or maternal age at first birth. The decreased risk of testicular cancer among later born sons was not modified by age, birth cohort, interval to the previous birth, sex of the first-born child, or maternal age at birth of the son or at first birth. The increased proportion of first-borns from birth cohort 1946 to birth cohort 1969 only explained around 3% of an approximated two-fold increase in incidence between the cohorts. Our data document a distinctly higher risk of testicular cancer in first-born compared with later born sons and suggest that the most likely explanation should be sought among exposures in utero. The increase in the proportion of first-borns in the population has only contributed marginally to the increase in testicular cancer incidence.

Adolescent↗

Does the increased risk of preterm delivery in teenagers persist in pregnancies after the teenage period?

OBJECTIVE: To study the associations between low maternal age at first birth and the risks of very and moderately preterm birth, in first birth and in second successive birth in adulthood. DESIGN: Population-based cohort study. SETTING: Sweden. POPULATION Women aged less than 25 years at first birth (n = 275,933), having two successive live single births from 1973 through 1993. METHODS: Odds ratios with 95 percent confidence intervals were calculated to estimate the effect of low maternal age at first birth. Analyses of first births were adjusted for year of first birth and maternal education and in second births also for previous pregnancy outcomes and interpregnancy interval. MAIN OUTCOME MEASURES: Very preterm birth (less than 33 completed weeks) and moderately preterm birth (33-36 completed weeks). RESULTS: Compared with women aged 20 to 24 years at first birth, mothers aged 13 to 15 years were at increased risk of very preterm birth (odds ratio = 4.8). The corresponding risks among women aged 16 to 17 years at first birth were doubled (odds ratio = 2.3). The influence of maternal age on risks of moderately preterm birth was similar, although the age-related risks were lower. At second birth, risks of preterm birth were reduced in all age groups. However, mothers who were 17 years or less at first birth, faced, compared with mothers aged 20-24 years, significantly larger reduction in risks of very and moderately preterm birth. CONCLUSIONS: Our results suggest that there may be a biological effect of very young maternal age, affecting foremost very preterm birth.

Adolescent↗

Space time clustering of births in SIDS: do perinatal infections play a role?

The aetiology of sudden infant death syndrome (SIDS) remains uncertain; many causal pathways have been proposed. In this paper we have examined firstly the variation in the risk of SIDS with age, month of death and month of birth; and secondly the space time clustering of SIDS deaths, and, separately, space time clustering of their births. Data were obtained from the Office of Populations, Censuses and Surveys on all certified SIDS deaths in the period; children were assigned grid references for the address of birth and of death. Data on number of births were abstracted from published material. A log-linear modelling technique was used to investigate the separate effects of age, month of death and month of birth on the risk of SIDS. The Knox method was used to investigate space time clustering of deaths and of births of children who died of SIDS. Separate, statistically significant effects were found for age, month of death and month of birth. There was minor space time clustering of SIDS births and deaths at large time and space intervals, and a marked space time clustering of births in short space time intervals in the first quarter of the year. The finding of an effect of month of birth on the risk of SIDS, and of space time clustering of births suggest that a perinatal hazard--possibly of infectious origin--may play a role in the aetiology of SIDS.

Birth Intervals↗

First cesarean birth and subsequent fertility.

OBJECTIVE: To determine whether cesarean delivery is independently associated with later subfertility. DESIGN: Retrospective cohort study. SETTING: Maternity records kept for Scotland, 1980-1999. PATIENT(S): The study included 109,991 women who had first births between 1980 and 1984, excluding multiple or preterm births and perinatal deaths. INTERVENTION(S): Exposures studied were spontaneous vaginal birth, operative vaginal birth, planned cesarean delivery for breach presentation, planned cesarean delivery for other indications, and emergency cesarean delivery. MAIN OUTCOME MEASURE(S): The relative risk of not having a second pregnancy over the following 15 years, the interpregnancy interval, and the number of spontaneous early pregnancy losses between the first and second birth. RESULT(S): Women who delivered by planned cesarean section for breech presentation had an increased risk of not having a second birth compared with women whose first birth was a spontaneous vertex delivery (relative risk [RR]: 1.21, 95% confidence interval [CI]: 1.14 to 1.29). However, after adjustment for maternal and obstetric characteristics, there was no longer a strong association (adjusted RR: 1.07, 95% CI: 1.00 to 1.15). Operative vaginal delivery (forceps and vacuum extraction) and all types of cesarean delivery were associated with longer interpregnancy intervals. There was no relationship between mode of delivery and the number of spontaneous early pregnancy losses between the first and second birth. CONCLUSION(S): It is unlikely that delivering by cesarean section in a first pregnancy decreases a woman's likelihood of having a second viable pregnancy.

Abortion, Spontaneous↗

Gender-specific association of the factor V Leiden mutation with fertility and fecundity in a historic cohort. The Leiden 85-Plus Study.

BACKGROUND: Factor V Leiden (FVL, Arg506Gln) mutation may facilitate embryo implantation and increase fertility and fecundity. This was studied in subjects who were of childbearing age in a time with minimal fertility control without modern contraceptive methods. METHODS: From 1986 to 1999, 1502 inhabitants of Leiden, The Netherlands, reaching the age of 85 years were enrolled in the Leiden 85-Plus Study. Of 1176 subjects the FVL status was analysed, in 365 male and 811 female subjects. RESULTS: The FVL carrier rate was 4.3%. Fertility was not affected by FVL status. In male subjects, fecundity (interval between marriage and birth of first child) was significantly increased in FVL carriers; 67% of male FVL carriers had a child within 371 days of marriage (therefore conceived within 3 months of marriage), compared with 19% of male non-carriers [relative risk (RR), 3.5; 95% confidence interval (CI), 2.1-5.7; P < 0.001]. Within 6 months of marriage, 75% of male FVL carriers had conceived a child compared with 34% male non-carriers (RR, 2.2; 95% CI, 1.5-3.2; P = 0.01). In female subjects, fecundity was not influenced by FVL status. CONCLUSION: Fecundity is increased in male FVL carriers; in female subjects, no such association was observed.

Aged, 80 and over↗

Determinants of invasive vulvar cancer risk: an Italian case-control study.

Risk factors for vulvar cancer have been evaluated in a case-control study conducted between 1987 and 1990 in northern Italy on 73 women with histologically confirmed invasive vulvar cancer and 572 control subjects in hospital for acute nongynecological, nonneoplastic non-hormone-related conditions. The risk of vulvar cancer was inversely related to education level: with reference to women reporting less than 7 years of schooling, the relative risk estimates were 0.6 and 0.4, respectively, in those reporting 7 to 11 and 12 or more years of schooling (chi 2(1) trend = 4.91 P = 0.03). No relationship emerged between number of births and spontaneous or induced abortions. Parous women reporting late first birth tended to be at lower risk (relative risk = 0.5, 95% confidence interval 0.3 to 1.1 for < 25 vs > or = 25 years at first birth), but there was no evidence of the risk to decrease with increasing age at first birth. The risk of vulvar cancer increased with body mass index, but the trend in risk was not significant after taking into account potential confounders in the multivariate analysis. No association emerged with indicators of sexual habits, menstrual history, and smoking. The risk of the disease was lower in women reporting Pap smears during their life and diminished with increasing number of cervical smears and decreasing recency of last Pap: compared to women reporting no Pap screening, it was 0.5 in those who reported one smear and 0.3 in those with two or more.

Adult↗

Consanguinity and recurrence risk of birth defects: a population-based study.

Recurrence risks give insight into the causes of birth defects and are useful in genetic counseling. There are few population-based studies of recurrence of birth defects for subsequent sibs with consanguineous parents. The aim of this study was to estimate and compare the recurrence risk of birth defects for offspring of first cousins and nonconsanguineous parents. The study population consisted of all single births with a previous sib born in Norway between 1967 and 1995. Altogether 660,398 children had nonconsanguineous parents, and 3,583 had parents who were first cousins. For nonconsanguineous parents the risk of a birth defect for the subsequent sib was 15 per 1,000 births (95% confidence interval: 14.5-15.1) if the previous child did not have a birth defect and 33 (95% confidence interval: 30-37) if the previous child had a birth defect. For parents who were first cousins the risk of a birth defect for the subsequent sib was 36 per 1,000 (95% confidence interval: 30-42) if the previous child did not have a birth defect and 68 (95% confidence interval: 33-122) if the previous child had a birth defect. The risk of recurrence of birth defects is higher for subsequent sibs with first-cousin parents than for those with nonconsanguineous parents. This difference indicates the degree to which the increased homozygosity among offspring of consanguineous parents influences the risk of recurrence of birth defects.

Age Factors↗

Adverse effects of human leukocyte antigen-DR sharing on fertility: a cohort study in a human isolate.

To elucidate further the reproductive effects of human leukocyte antigen (HLA) sharing among spouses, we have been investigating prospectively the relationship between HLA-A, -B, and -DR sharing and reproductive outcome in the Hutterites, a religious isolate that proscribes contraception. For the first time the reproductive effects of HLA-DR sharing in a fertile population is reported in this article. Median intervals from marriage to first through fifth births were longer among couples who shared more than one HLA-A, -B, or -DR antigen. Longer intervals were associated with increased spontaneous abortion rates among couples who shared HLA-DR antigens (27%), compared with couples who shared only HLA-A or -B antigens (9%) and couples who shared no antigens (12%). Median completed family sizes were 5.0, 8.5, and 8.0 among the groups, respectively. However, some couples who shared HLA-DR antigens experienced no spontaneous abortions, despite ten or more pregnancies. Therefore, although HLA-DR compatibility, per se, is not deleterious, our data suggest a potentially important role for undefined HLA-linked genes in normal pregnancy.

Abortion, Spontaneous↗

Postpartum sexual abstinence, breastfeeding, and childspacing, among Yoruba women in urban Nigeria.

This paper examines the extent to which the traditional practice of sexual abstinence during lactation has broken down among Yoruba women residents in urban areas. The first major finding is that there is a gradual erosion of the tradition, and the dominant factors of modernization are education of the woman and the use of contraception. The second major finding is that the breakdown of postpartum sexual taboos has statistically significant negative consequences on duration of lactation, although the negative impact of woman's education is greater. The third major finding is that duration of breastfeeding reduces birth interval significantly only when it is less than 15 months, and that both durations of breastfeeding and birth intervals have declined over time. The first two findings suggest further reductions in the proportion of women who abstain from sexual relations during lactation and in durations of breastfeeding as more women become more educated. Significant declines in birth intervals may follow soon after.

Adult↗

A study of change in age at first marriage and first fertility of Chinese women and population control.

The author examines the decline in Chinese women's "age at first marriage..., going on to analyze trends of development in women's average age at first marriage and changes in the interval before first fertility over the last few decades, and from there proposes an effective way to alleviate the population peak and control the population--gradually lengthening the interval before first fertility on the basis of maintaining the average age at first marriage." Data are from the 1982 census and other official sources.

Asia↗

Interpregnancy interval. Association with birth weight, stillbirth, and neonatal death.

Pairs of first and second births and pairs of second and third births to the same Norwegian mothers were studied to determine the association between interpregnancy interval and birth weight, stillbirth, and neonatal death. Use of the pair approach provides one birth which could possibly have been affected by the length of the interval and one birth which could not. The association of interval and birth weight for births which precede an interval is found to be equivalent to that for births which follow an interval. The data on stillbirth are compatible with higher rates at long intervals while the data on neonatal death are consistent with higher rates at short intervals. However, we conclude that manipulation of the interval between pregnancies is unlikely to have any marked, direct, beneficial effect on outcome of pregnancy.

Birth Order↗

Recurrence of spontaneous versus medically indicated preterm birth.

OBJECTIVE: Despite the increased tendency of preterm birth to recur, little is known with regard to recurrence risks for spontaneous and medically indicated preterm birth as well as recurrence risks in relation to severity of preterm birth. We examined the recurrence of spontaneous and medically indicated preterm birth. STUDY DESIGN: A population-based, retrospective cohort study of births in Missouri (1989 to 1997) was carried out with analyses restricted to women who delivered their first 2 consecutive singleton live births (n = 154,809). Women who experienced spontaneous onset of labor and subsequently delivered preterm (less than 35 weeks) were classified as spontaneous preterm birth. Medically indicated preterm birth included women who delivered preterm through a labor induction or a prelabor cesarean delivery. Risk and odds ratio of preterm birth recurrence were derived from fitting multivariate conditional logistic regression models after adjusting for potential confounders. RESULTS: If the first pregnancy resulted in a spontaneous preterm birth, then affected women were more likely to deliver preterm spontaneously (adjusted odds ratio 3.6, 95% confidence interval 3.2, 4.0) and also as a medically indicated preterm birth (odds ratio 2.5, 95% confidence interval 2.1, 3.0) in the second birth. Similarly, if the first pregnancy resulted in a medically indicated preterm birth, affected women were 10.6-fold (95% confidence interval 10.1, 12.4) more likely to deliver preterm because of medical indications in the second pregnancy as well as preterm spontaneously (odds ratio 1.6, 95% confidence interval 1.3, 2.1). The greatest risk of recurrence of preterm birth in the second pregnancy tended to occur around the same gestational age as preterm birth in the first pregnancy, regardless of the clinical subtype. CONCLUSION: The observation that spontaneous preterm birth is not only associated with increased recurrence of spontaneous but also medically indicated preterm birth and vice versa, suggests that the 2 clinical subtypes may share common etiologies.

Adult↗

Risk factors for pre-eclampsia in nulliparous and parous women: the Jerusalem perinatal study.

Pre-eclampsia has been described as a 'disease of first pregnancies' and many believe that its occurrence in a later pregnancy signals a fundamentally different entity. We sought to compare risk factors in first and subsequent pregnancies. We studied 1319 cases of pre-eclampsia recorded in a historical cohort of 82,436 deliveries in Jerusalem in 1964-76. Logistic regression was used to control for covariates. The adjusted odds ratio (OR) for pre-eclampsia in first births was 2.58 (95% confidence interval[CI] 2.23, 2.97), compared with all later birth order groups, between which there were no detectable differences in risk. Other risk factors included increasing maternal age, diabetes (OR 5.64, 95% CI 4.33, 7.35), multiple gestations (OR 3.38, 95% CI 2.54, 4.49), fetal haemolytic disease (OR 2.24, 95% CI 1.43, 3.50) and lower maternal education. The risk of pre-eclampsia was not associated with the mother's employment outside the home and did not differ between immigrants vs. Israeli-born mothers or between groups of women whose fathers had been born in Western Asia, North Africa or Europe. Effects of each risk factor were similar within first and subsequent births. These results lend no support to the hypothesis that there is a fundamental difference between pre-eclampsia in a first pregnancy compared with that occurring in a later pregnancy; conclusions may be moderated, however, by the knowledge that the incidence of pre-eclampsia was low in this historical cohort.

Adolescent↗

Effects of home visits by paraprofessionals and by nurses: age 4 follow-up results of a randomized trial.

OBJECTIVE: To examine the effects of prenatal and infancy home visiting by paraprofessionals and by nurses from child age 2 through age 4 years. METHODS: We conducted, in public and private care settings in Denver, Colorado, a randomized, controlled trial with 3 arms, ie, control, paraprofessional visits, and nurse visits. Home visits were provided from pregnancy through child age 2 years. We invited 1178 consecutive, low-income, pregnant women with no previous live births to participate, and we randomized 735; 85% were unmarried, 47% Mexican American, 35% white non-Mexican American, 15% black, and 3% American Indian/Asian. Outcomes consisted of maternal reports of subsequent pregnancies, participation in education and work, use of welfare, marriage, cohabitation, experience of domestic violence, mental health, substance use, and sense of mastery; observations of mother-child interaction and the home environment; tests of children's language and executive functioning; and mothers' reports of children's externalizing behavior problems. RESULTS: Two years after the program ended, women who were visited by paraprofessionals, compared with control subjects, were less likely to be married (32.2% vs 44.0%) and to live with the biological father of the child (32.7% vs 43.1%) but worked more (15.13 months vs 13.38 months) and reported a greater sense of mastery and better mental health (standardized scores [mean = 100, SD = 10] of 101.25 vs 99.31 and 101.21 vs 99.16, respectively). Paraprofessional-visited women had fewer subsequent miscarriages (6.6% vs 12.3%) and low birth weight newborns (2.8% vs 7.7%). Mothers and children who were visited by paraprofessionals, compared with control subjects, displayed greater sensitivity and responsiveness toward one another (standardized score [mean = 100, SD = 10] of 100.92 vs 98.66) and, in cases in which the mothers had low levels of psychologic resources at registration, had home environments that were more supportive of children's early learning (score of 24.63 vs 23.35). Nurse-visited women reported greater intervals between the births of their first and second children (24.51 months vs 20.39 months) and less domestic violence (6.9% vs 13.6%) and enrolled their children less frequently in preschool, Head Start, or licensed day care than did control subjects. Nurse-visited children whose mothers had low levels of psychologic resources at registration, compared with control group counterparts, demonstrated home environments that were more supportive of children's early learning (score of 24.61 vs 23.35), more advanced language (score of 91.39 vs 86.73), superior executive functioning (score of 100.16 vs 95.48), and better behavioral adaptation during testing (score of 100.41 vs 96.66). There were no statistically significant effects of either nurse or paraprofessional visits on the number of subsequent pregnancies, women's educational achievement, use of substances, use of welfare, or children's externalizing behavior problems. CONCLUSIONS: Paraprofessional-visited mothers began to experience benefits from the program 2 years after the program ended at child age 2 years, but their first-born children were not statistically distinguishable from their control group counterparts. Nurse-visited mothers and children continued to benefit from the program 2 years after it ended. The impact of the nurse-delivered program on children was concentrated on children born to mothers with low levels of psychologic resources.

Birth Intervals↗