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PubMed1987

Fecundity and size in the housefly: investigations of some environmental sources and genetic correlates of variation.

Environmental sources and genetic correlates of variation in fecundity and size were studied in field and laboratory housefly populations in central Iowa, U.S.A. Electrophoresis of enzymatic proteins was used to monitor genotypes and heterozygosity. In the field, mean fecundity declined as adult densities increased. Fecundity varied greatly within breeding seasons. Fly body size varied spatially and temporally during summer and winter. Fecundity and size were positively correlated. Size was independent of genotypes at the six loci studied. No relationship was observed between heterozygosity and the magnitude or variability of body size.

Analysis of Variance↗
PubMed1986

Fecundability rates from an infertile male population.

From a computer file of 955 couples attending hospital because of an infertile marriage, 279 were identified where the female partner had normal investigation results. Follow-up information was available for all couples and the fecundability (conception rate per month) for the first year of follow-up has been calculated, stratified according to the husband's investigation results. The fecundability of couples where the wife had normal investigation results but the husband had reduced sperm density ranged from 0.4% for wives with azoospermic husbands to 5.9% when the husband had at least 10 million motile sperm/ml. For any given number of motile sperm the fecundability was also strongly dependent on the duration of involuntary infertility as recorded at the time of initial clinic attendance. In view of the lack of effective treatment for most male infertility the fecundability rates reported herein are likely to represent those that would be found in an untreated population and should be useful as a base line when evaluating results of new treatments.

Female↗
PubMed1981

Social selection in seeking medical care for reduced fecundity among women in Denmark.

This study is based on a representative sample of 709 Danish women aged between 25 and 45 who were interviewed in 1979. The purpose was to estimate the proportion of women with reduced fecundity who seek medical care and to identify sociodemographic variables associated with presentation to the medical care system. The study showed that the majority of women with reduced fecundity did not seek medical care. The propensity to seek care was not significantly associated with a woman's age or education, nor with family income or the employment status of the head of the household. Women living in rural areas or in homes with two or more rooms per family member had a greater tendency to seek medical care for secondary reduced fecundity compared with women living in cities or in more crowded homes. The implications of these findings for epidemiological studies of the association of reduced fecundity and occupation are discussed.

Adult↗
PubMed2002

Complete removal of endometriosis improves fecundity.

Endometriosis is one of the causative factors of impaired fecundity. Whatever the mechanisms are of this impairment, surgical removal of endometriosis appears to increase postoperative fecundity. Our strategy in laparoscopic surgery for symptomatic endometriosis is to completely remove endometriosis. However, despite this strategy, laparoscopic surgery nonetheless creates two categories of patients; complete and incomplete surgery groups. We found by comparing the two groups that both were comparable in terms of fecundity during the early postoperative phase, whereas unlike the complete surgery group, fecundity in the incomplete surgery group stayed low during the late postoperative phase. Deep rectal endometriosis and deeply invading pelvic endometriosis are conditions wherein complete removal of endometriosis is difficult. We have developed laparoscopic surgeries for these conditions: laparoscopic anterior rectum slicing (LARS) and laparoscopic pelvic wall slicing (LPWS) operations, respectively. Both operations are effective in alleviating disease-related symptoms with minimal surgical invasiveness.

Adult↗
PubMed2004

How an individual fecundity pattern looks in Drosophila and medflies.

Reproduction usually is characterized by a mean-population fecundity pattern. Such a pattern has a maximum at earlier ages and a subsequent gradual decline in egg production. It is shown that individual fecundity trajectories do not follow such a pattern. In particular, the regular individual fecundity pattern has no maximum so that experimentally observed maximums are average-related artifacts. The three-stage description of individual fecundity, which includes maturation, maturity, and reproductive senescence, is more appropriate. Data are presented for Drosophila and Mediterranean fruitfly females that clearly confirm this hypothesis. A systematic error between egg-laying scores and the regular individual pattern allows for evaluation of how close the random scores are to the pattern. The first finding of the analysis of the systematic errors is that they are consistent with the three-stage hypothesis and do not contradict the absence of the maximum in the regular individual pattern. The other finding is the existence of obvious dynamic properties of the systematic error. The slow decrease in egg-laying at the maturity stage might be the result of a cost of mating. It can also be a consequence of "structural" senescence, that is, a slow rate accumulation of oxidative damage in the gonads.

Aging↗
PubMed1999

Phenology and fecundity in 11 sympatric pioneer species of Macaranga (Euphorbiaceae)in Borneo.

Reproductive traits of tropical tree species vary predictably in relation to successional stage, but this variation may be due to the species' phylogenetic histories rather than selective pressures imposed by regeneration requirements. Reproductive phenology, tree size at the onset of reproduction, and fecundity of 11 sympatric, closely related Macaranga species were studied to investigate within-species variation in reproductive traits in relation to resource availability, and among-species variation in relation to other life-history traits (shade tolerance, seed size and maximum tree size, H(max)) and consequently the requirements for forest-gap colonization. Nine species reproduced in synchronous episodes, and two species reproduced continuously over 32 mo. Episodic reproduction was most intense in 1992 following a severe drought. For several species, reproductive trees had greater light availability, lower fecundity in lower light levels, and lower growth rates than nonreproductive trees, reflecting resource-limited reproduction. Among species, H(max) was negatively correlated with shade tolerance and seed size. Tree size at the onset of reproduction and fecundity was strongly linked to this axis of life-history variation, but phenological pattern was not. Absolute tree size at the onset of reproduction was positively correlated with H(max) and negatively correlated with shade tolerance. Relative size at reproductive onset was not correlated with shade tolerance or H(max). Fecundity ranged four orders of magnitude among species and was correlated positively with H(max) and negatively with seed size and shade tolerance. The interrelationships among these reproductive and other life-history traits are strongly correlated with the species' requirements for gap colonization.

Journal Article↗
PubMed1975

A method for the estimation of fecundability.

A new method for the estimation of the mean and variance of fecundability is described. The data input required for this procedure is the distribution of the interval from marriage to first birth, or from the resumption of the conception risk after contraction to the subsequent birth. The estimates of the mean and variance of fecundability are obtained by fitting a model to the observed interval distribution. To test the method, it is applied to data from five historical populations. The fecundability means in these populations ranged from 0.18 to 0.31 while the co-efficients of variation all had values near 0.56. A short method for the estimation of the mean of fecundability based on the same model, but not requiring a computer, is also presented.

Abortion, Spontaneous↗
PubMed2002

Fecundity of the Hypostomus affinis (Siluriformes, Loricariidae) in the Lajes Reservoir, Rio de Janeiro, Brazil.

The armored catfish Hypostomus affinis is a widespread Loricariidae fish in the Lajes Reservoir (22 degrees 42'-22 degrees 50' S; 43 degrees 53'-44 degrees 05' W), the largest lentic environment in the Rio de Janeiro State, but little is known about their reproductive biology. One hundred and twenty five females, captured from January 1996 to December 1997, were used to assess ovarian development (29 were used to determine fecundity). The oocyte distribution by size-diameter classes revealed the occurrence of two modes suggesting an asynchronic development of the ovaries. The total fecundity ranged from 1235 to 4304, averaging 2374. An exponential relationship between fecundity and total length was determined, and a direct linear relationship was found between fecundity and total weight and gonad weight.

Animals↗
PubMed2005

Does the Anopheles blood meal-fecundity curve, curve?

We determined the blood meal size-fecundity relationship in Anopheles gambiae in the laboratory. Our primary interest was to determine whether the fecundity curve has a non-linear component, i.e.. does it decelerate towards an asymptote? Small and large adult females in their second gonotrophic cycle were fed on human hosts for predetermined lengths of time. Blood meal size was ascertained by weight and subsequent fecundity was determined by the number of eggs laid on filter paper. In both small and large-bodied females there was a significant curvilinear component. We used this relationship to show that marginal returns from feeding decline as a function of current blood load. This means that further fecundity payoff for continued feeding declines over time.

Animals↗
PubMed2005

Fecundity of the freshwater fish, Notopterus notopterus (Pallas) in natural and heavy metal contaminated water.

The knowledge of fecundity of fish from a specific aquatic body is extremely important in the successful management and exploitation of its fishery. In the present investigation the fecundity of the freshwater fish, Notopterus notopterus was studied in fish collected from a natural aquatic body (Sirnoor nala) near Gulbarga and also in fish exposed to some heavy metal contamination (HgCl2, CdCl2 and their combination) at sublethal concentration for 15 days in the laboratory. The mathematical relationship between fecundity and total length, body weight, ovary length and ovary weight were determined in both unexposed and exposed fish. The fish, N. notopterus has bigger oocytes and are few in number. Studies in the fish exposed to heavy metals indicate that significant reduction in these parameters after exposure to heavy metals at sublethal concentration was noticed. The fecundity has straight line relationship with total length, body weight, ovary length and ovary weight in control fish which did not alter after heavy metal exposure. This study provides the viability of species in only specific environment.

Animals↗
PubMed1991

Gonadal protection and fecundity rates in cyclophosphamide-treated rats.

Premature ovarian failure and reduced fecundity are well-documented consequences of cytotoxic chemotherapy used to treat patients with malignant diseases. To investigate the ability of different hormonal agents to block the effects of cyclophosphamide (CTX) on reproductive function, sexually mature female Long-Evans rats were studied. Model development demonstrated that CTX, 6 mg/kg/day, 5 days/week for 3 weeks, was successful at inducing acyclicity and significantly reducing fertility and fecundity, with acceptable mortality, when compared to higher/lower dosages. Utilizing this model, animals were treated with CTX in combination with an inert vehicle, Lupron, 80 micrograms/kg every 24 h, Lupron, 40 micrograms/kg every 12 h, or s.c. progesterone capsules obtaining serum progesterone levels of 20-30 ng/ml. We concluded that progesterone was able to protect the gonad from the negative effects of CTX, maintaining fertility and fecundity rates not significantly different from those of untreated control animals. Lupron given every 12 h had a similar effect on fertility, but failed to protect fecundity (P less than 0.001).

Animals↗
PubMed1990

The effect of Schistosoma haematobium infection on the growth and fecundity of three sympatric species of bulinid snails.

Three species of bulinid snails were monitored to determine the effect of infection with 2 sympatric strains of Schistosoma haematobium on longevity, growth, and reproductive output, from the onset of cercarial production until death. Bulinus senegalensis was least affected by infection, with total fecundity reduced by less than 34%. Infected Bulinus truncatus showed an acceleration in growth accompanied by a 63% reduction in fecundity, although the majority of snails continued to oviposit at a low level. The longest-lived snails in this study, Bulinus globosus, showed decreased growth and survival when infected. In addition a significant proportion of infected individuals of this species failed to oviposit, and those that retained some reproductive capacity produced fewer embryos than controls. Total fecundity of B. globosus was reduced almost 90% by infection with S. haematobium, yet long-term monitoring of individuals showed that reproductive activity recovered when parasite productivity was low. Results from this and similar studies indicate that the time of infection by a trematode in relation to reproductive maturity of the molluscan host is important in determining the subsequent effects on host growth and fecundity.

Animals↗
PubMed1994

Is human fecundity declining--and does occupational exposures play a role in such a decline if it exists?

Demographers have analyzed fertility over time and between many populations for many decades. Much less is known about fecundity. Recent publications seem to indicate a decline in semen quality over time, but still no good data corroborate or refute this hypothesis. The very sparse data do not indicate any substantial changes in fecundity over the last 10-30 years in the United States, but none of the studies have a comparability which permit any firm conclusion. Several chemical and physical exposures interfere with human fecundity. Some are found at the worksite, sometimes in an intensity which does harm. The marked effect of dibromochloropropane on semen quality and fecundity was a clear warning to occupational health workers. Several other occupational exposures have shown an effect on gonads in men or women, and it is time to give more research priority to the topic. The rapidly rising cost of infertility treatment could be the stimulus to trigger the development of this research field.

Female↗
PubMed1991

Reporting errors in time-to-pregnancy data collected with a short questionnaire. Impact on power and estimation of fecundability ratios.

Few tools exist in reproductive epidemiology for studying adverse effects on fertility. Data on time to pregnancy (the number of menstrual cycles required to conceive) can be used to estimate fecundability ratios, a sensitive endpoint for identifying factors associated with reduced fertility. Time-to-pregnancy data can be collected in detailed interviews. The accuracy of data collected on brief, self-administered questionnaires is not known. In a study of occupational exposures to dental assistants conducted in 1987-1988, 523 women provided time-to-pregnancy data both on a short, mailed questionnaire and in a detailed telephone interview. The correlation between the two measures was 0.82. Assuming that the detailed data were accurate, reporting errors in data from the short form were distributed nondifferentially with respect to most covariates of interest in fecundability analyses. Simulation studies were conducted to estimate bias and loss of power from the misclassification. Bias was toward the null. Substantial power was lost in detecting weak exposures. However, exposures that reduce fecundability by 50 percent (equivalent to adding about three cycles to the median time to pregnancy) could still be detected with 80 percent power in samples of about 100 women (half of them exposed to a possible toxin). The authors conclude that time-to-pregnancy data collected with a few self-administered questions can be useful in a variety of epidemiologic studies, including occupational and environmental surveillance programs.

Bias↗
PubMed2000

Daily fecundability: first results from a new data base.

This multicenter study has produced a database of 7017 menstrual cycles contributed by 881 women. It provides improved knowledge on length and location of the "fertile window" (identified as of up to 12 days duration) and the patterns and level of daily conception probability. The day of ovulation was identified in each cycle from records of basal body temperature and mucus symptoms. By referencing days of intercourse to the surrogate ovulation markers, estimates of daily fecundability were computed either directly or by the Scwartz model, both for single and multiple acts of intercourse in the fertile window. The relationship between coital pattern and fecundability has been explored. Univariate analysis underlines the significant link with fecundability only of the woman's reproductive history.

Developed Countries↗
PubMed1993

Estimation of fecundability of migrated couples in the process of rural out-migration in India.

"Based on a simple procedure developed by Menken (1979), the estimate of fecundability of migrated couples in the process of rural out-migration [in India] has been obtained in this paper. It is found that the estimates of fecundabilities for females of different age-groups are significantly larger than the level of fecundability estimated for non-migrated couples. Some possible explanations for observing such a large gap [are] given."

Asia↗
PubMed1986

The beta-geometric distribution applied to comparative fecundability studies.

A convenient measure of fecundability is time (number of menstrual cycles) required to achieve pregnancy. Couples attempting pregnancy are heterogeneous in their per-cycle probability of success. If success probabilities vary among couples according to a beta distribution, then cycles to pregnancy will have a beta-geometric distribution. Under this model, the inverse of the cycle-specific conception rate is a linear function of time. Data on cycles to pregnancy can be used to estimate the beta parameters by maximum likelihood in a straightforward manner with a package such as GLIM. The likelihood ratio test can thus be employed in studies of exposures that may impair fecundability. Covariates are incorporated in a natural way. The model is illustrated by applying it to data on cycles to pregnancy in smokers and nonsmokers, with adjustment for covariates. For a cross-sectional study, when length-biased sampling is taken into account, the pre-interview attempt time is shown to follow a beta-geometric distribution, so that the same methods of analysis can be applied even though all of the available data are right-censored. For a cohort followed prospectively, there will be some couples enrolled whose fecundability is effectively 0, and for such applications, the beta could be considered to be contaminated by a distribution degenerate at 0. The mixing parameter (proportion sterile) can be estimated by application of the expectation-maximization (EM) algorithm. This, too, can be carried out using GLIM.

Biometry↗
PubMed1986

Abortions in relation to age, coital frequency, and fecundity.

Abortion rates show variations by age in the United States. This article addresses the question of age variations in abortions. Since the probability of pregnancy is increased in direct proportion to increased coital frequency, age and coitus-specific abortion rates are calculated. Since the probability of pregnancy is related to fecundity, age and fecundity abortion rates are also calculated. When combining coital frequency and fecundity with the age-specific abortion rates, the variation by age disappears for all women except teen-agers.

Abortion, Induced↗