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PubMed2004

Association between short birth intervals and schizophrenia in the offspring.

Pregnancy burdens maternal folate reserves. Postpartum restoration to normal folate values may take up to 1 year. Maternal folate deficiency during early pregnancy has been hypothesized as a cause of schizophrenia in the offspring. We investigated whether the risk of schizophrenia is increased in persons conceived shortly after another birth. A population-based cohort was established of 1.43 million persons born in Denmark between 1950 and 1983, yielding 17.6 million person-years of follow-up. Schizophrenia in cohort members (5095 cases) and their siblings and parents was identified by linkage with the Danish Psychiatric Case Register. Relative risks of schizophrenia were estimated by use of log-linear Poisson regression. As compared to intervals of 45 months and longer, the schizophrenia risk ratio was 1.14 (95% confidence interval [CI], 0.97 to 1.35) for interbirth intervals of up to 15 months, 1.32 (95% CI, 1.12 to 1.56) for intervals of 15 to 17 months, 1.38 (95% CI, 1.18 to 1.61), for intervals of 18 to 20 months and 1.13 (95% CI, 1.00 to 1.29) for intervals of 21 to 26 months. Relative risks did not essentially change after adjustment for age, sex, calendar year of diagnosis, maternal and paternal age, history of mental illness in a parent or sibling, sibship size, place of birth, and distance to younger sibling. These results show an association between short birth intervals and schizophrenia in the offspring. Although maternal folate depletion may play a role in this association, we cannot rule out other explanations such as maternal stress during pregnancy and childhood infections.

Adult↗
PubMed1982

Nutrition, lactation, and birth interval components in rural Guatemala.

The effects of maternal nutritional status and food supplementation ingested by the infant on the duration of postpartum amenorrhea and on the duration of the menstruating interval was examined. A significant negative association was found between the nutritional status of the mother during the 3rd trimester of pregnancy and infant supplementation, on the one hand, and the length of postpartum amenorrhea on the other hand. These associations remained significant after controlling for each other and for other potentially confounding factors for which data wee collected. These results support the hypothesis that maternal nutritional status, by determining the amount of breast milk available, hence the frequency, duration, and intensity of suckling, is indirectly, negatively associated to the length of postpartum amenorrhea. Furthermore, no association between maternal nutritional status and the length of the menstruating interval was found.

Adult↗
PubMedDate not supplied

Malaria specific-IgG, inter-pregnancy intervals, birth weights and body mass index in cases of asymptomatic malaria parasitaemia.

BACKGROUND & OBJECTIVES: Considerations of both inter-pregnancy intervals and malaria parasitaemia may help in understanding some aspects of susceptibility and pregnancy outcomes in malaria endemic areas. METHODS: Pregnant women with asymptomatic malaria parasitaemia were recruited and divided into groups based on their inter-pregnancy intervals and malaria specific-IgG, body mass index, and birth weights were studied in the groups. RESULTS: The results showed that the P. falciparum specific-IgG concentration (f=3.52, p<0.02), malaria parasites density (f=6.44, p<0.001) and birth weights (f=7.36, p<0.001) were significantly different amongst the groups with varying inter-pregnancy intervals. In addition, different levels of associations between variables such as 'inter-pregnancy intervals vs P. falciparum specific-IgG concentration' (r = 0.23, p<0.05); 'malaria parasites density vs birth weight' (r = -0.84, p < 0.01) was observed. INTERPRETATIONS & CONCLUSION: This study suggests that inter-pregnancy intervals could be one of the factors influencing dynamic serum concentrations of P. falciparum specific-IgG while malaria parasitaemia could be one of the factors affecting birth weights. Hence, observance of inter-pregnancy intervals has its own implications in malaria endemic areas.

Analysis of Variance↗
PubMed1987

Breast feeding, birth interval and polygyny in Nigeria.

Polygyny has routinely been claimed to facilitate rules and taboos relating to postpartum sexual abstinence. However, in Nigeria polygyny cannot wholly explain length of postpartum taboo following child birth on the ground that competition among cowives to out do one another in child-bearing results in a tendency of higher fertility and hence shorter postpartum taboo in polygynous households than that in monogamous families. Economic factors have been adduced as reasons explaining the recent tendency for mothers in polygynous families to have longer postpartum abstinence than their counterparts in monogamous households. Specifically, for young mothers aged 15-34, bearing children in quick succession is no longer attractive as in essentially traditional cultures where husband's commitment to caring for children is taken for granted. Hence, the tendency for women in polygynous households to adhere more strictly to rules and taboos relating to postpartum abstinence could be associated to the changing roles of women as they affect their responsibility with respect to the maintenance and training of their children rather than to the institution of polygyny per se.

Adolescent↗
PubMed1981

Infant-related influences on birth intervals in rhesus monkeys.

That a mother's relationship with her infant could influence her subsequent reproductive history can be argued as follows. A rhesus monkey infant whose next sibling is to be born in a succeeding birth season could compete with it by trying to postpone the date when its mother next conceives. If the mother preferred a shorter delay than the infant, processes of conflict and negotiation involving the two could show in some of the behavioural interactions constituting their relationship. For example, a mother could try to hasten the onset of her next pregnancy by trying to promote more independent behaviour in her infant, perhaps by rejecting some of its bids for contact. We report here studies on our rhesus monkey colony and other colonies which support this argument.

Animal Population Groups↗
PubMed1986

The determinants of effective fecundability based on the first birth interval.

There are substantial differences in fecundability among nine developing countries in different parts of the world. In addition, within countries, later age at marriage has a clear, positive, nonlinear effect on fecundability. Women with higher education and those with more educated husbands have higher fecundability. Urban residents have higher fecundability than rural. The higher fecundability of more recent cohorts is the most consistent observation. Since those variables most frequently shown to have inverse relationships to fertility show direct relationships to fecundability within populations, the role of fecundability as a proximate variable in models of the determinants of fertility requires further specification.

Adult↗
PubMed2007

Genetic relationships among calving ease, calving interval, birth weight, and weaning weight in the Asturiana de los Valles beef cattle breed.

The aim of this paper was to estimate direct and maternal genetic parameters for calving ease (CE), birth weight (BrW), weaning weight (WW), and calving interval (CI) to assess the possibility of including this information in beef cattle improvement programs. Field data, including a total of 59,813 animals (1,390 sires and 1,147 maternal grand sires) from the Asturiana de los Valles beef cattle breed, were analyzed with a multivariate linear model. Estimates of heritability for direct genetic effects (CED, CID, BrWD, and WWD) were 0.191 +/- 0.019, 0.121 +/- 0.013, 0.390 +/- 0.030, and 0.453 +/- 0.035, respectively, whereas those for maternal genetic effects (CEM, BrWM, and WWM) were 0.140 +/- 0.015, 0.208 +/- 0.020, and 0.138 +/- 0.022, respectively. Genetic correlations between direct or maternal genetic effects across traits were, in general, positive and moderate to low. However, genetic correlation for the pair CED-BrWD was positive and high (0.604 +/- 0.064). Genetic correlations between the direct and maternal genetic effects within a trait were negative and moderate (-0.219 +/- 0.097 for CE, -0.337 +/- 0.080 for BrW, and -0.440 +/- 0.102 for WW). Genetic correlations for CED-BrWM and CED-WWM were -0.121 +/- 0.090 and -0.097 +/- 0.113, respectively. The genetic correlation for CEM-CID was unfavorable (0.485 +/- 0.078), and those for CEM-BrWD (-0.094 +/- 0.079) and CEM-WWD (-0.125 +/- 0.082) were low and negative. The genetic correlation between CID and WWM was favorable (-0.148 +/- 0.106). Overall, the data presented here support the hypothesis that maternal effects for CE and BrW are not the same and that the genetic relationships between CI and maternal effects for WW in beef cattle follow a similar pattern to that reported between CI and milk yield in dairy cattle. Moreover, the need to include direct and maternal breeding values in beef cattle selection programs is suggested.

Animals↗