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PubMed1993

The risk of male subfecundity attributable to welding of metals. Studies of semen quality, infertility, fertility, adverse pregnancy outcome and childhood malignancy.

These studies were initiated by the results of two Danish investigations of infertility clients, which indicated the reduced fecundity of male metal welders. The objective was to refute or corroborate the effects of welding on male reproductive capability and--if there was any effect--to identify the causal exposures. The initial hypothesis postulated reduced spermatogenesis, spontaneous abortion, congenital malformation and childhood malignancy following exposure to hexavalent chromium among stainless steel welders. Subsequently, a hypothesis concerned with the significance of exposure to radiant heat on reduced semen quality was put forward. These studies comprised a case-referent study of infertility, cross-sectional and longitudinal studies of semen quality and historical cohort studies of fertility, pregnancy outcome and cancer in offspring. Exposure to welding was reported with a higher frequency during periods of infertility than prior to conception in the case-referent study (OR 2.0, 95% CI 1.0-4.0). This finding is consistent with the main cross-sectional study showing reduced semen quality in welders [average reduction ranging from 8% (sperm penetration rate in eggwhite) to 28% (total sperm count)] and with the cohort study revealing reduced fertility in relation to welding (OR 0.89, 95% CI 0.83-0.97). However, reduced semen quality and fertility were not attributable to the welding of stainless steel but to the welding of mild steel; and no relationship was found between biological measures of exposure to chromium and parameters of semen quality. If the unexpected association between mild steel welding and reduced fecundity is causal, the biological mechanisms involved are obscure. A separate longitudinal study leaves little doubt that moderate radiant heat exposure may cause reversible deterioration of semen quality, but it is not justified to generalize this observation to the entire population of welders. Male-mediated effects on occurrence of congenital malformation and cancer in offspring from stainless steel welding are not indicated by the studies. Weak indications of an increased risk of spontaneous abortion among partners to stainless steel welders (OR 1.9, 95% CI 1.1-3.2) need to be refuted or corroborated in future studies. Suggested effects of mild steel welding on male fecundity should be corroborated by longitudinal controlled studies of semen quality examined before and during exposure and by prospective studies of fecundability in couples trying to conceive a child. On account of the present knowledge it is not possible to recommend rational preventative measures with the exception of elimination of radiant heat exposure in cases of infertility.(ABSTRACT TRUNCATED AT 400 WORDS)

Cohort Studies↗
PubMed2005

Pollen flow in the wildservice tree, Sorbus torminalis (L.) Crantz. II. Pollen dispersal and heterogeneity in mating success inferred from parent-offspring analysis.

Knowing the extent of gene movements from parents to offspring is essential to understand the potential of a species to adapt rapidly to a changing environment, and to design appropriate conservation strategies. In this study, we develop a nonlinear statistical model to jointly estimate the pollen dispersal kernel and the heterogeneity in fecundity among phenotypically or environmentally defined groups of males. This model uses genotype data from a sample of fruiting plants, a sample of seeds harvested on each of these plants, and all males within a circumscribed area. We apply this model to a scattered, entomophilous woody species, Sorbus torminalis (L.) Crantz, within a natural population covering more than 470 ha. We estimate a high heterogeneity in male fecundity among ecological groups, both due to phenotype (size of the trees and flowering intensity) and landscape factors (stand density within the neighbourhood). We also show that fat-tailed kernels are the most appropriate to depict the important abilities of long-distance pollen dispersal for this species. Finally, our results reveal that the spatial position of a male with respect to females affects as much its mating success as ecological determinants of male fecundity. Our study thus stresses the interest to account for the dispersal kernel when estimating heterogeneity in male fecundity, and reciprocally.

Conservation of Natural Resources↗
PubMed2000

Laparoscopic surgery for endometriosis: a long-term follow-up.

OBJECTIVE: To investigate if complete resolution of endometriosis by laparoscopic surgery is beneficial to postoperative fecundity, dysmenorrhea and dyspareunia. DESIGN: An observational comparative study on the outcome of laparoscopic surgery. PATIENTS: Laparoscopically-treated symptomatic women with endometriosis (total n = 236); complete (n = 185) and incomplete (n = 51) surgery groups. MEASUREMENTS: Postoperative fecundity and symptom reduction. RESULTS: With whole populations, no surgical completeness-related difference was observed in cumulative pregnancy rates during the postoperative days 0-400 (cycle fecundity rate = 0.0319). Further accumulation of pregnant cases was followed in the complete surgery group (final cumulative pregnancy rate = 80%), but not in the counterpart group (p = 0.003). The similar result was obtained when only r-AFS classification stages III and IV were compared (p = 0.007). No r-AFS stage-related difference was observed in cumulative pregnancy rates when only patients of complete surgery were selected for comparison. The surgery reduced dysmenorrhea (84.7%) and dyspareunia (80.0%). CONCLUSIONS: Laparoscopic conservative surgery for endometriosis, especially when it is complete, increases fecundity and reduces disease-related symptoms, such as dysmenorrhea and dyspareunia.

Adult↗
PubMed1977

Reproductive strategy of winged and wingless morphs of the aphids Sitobion avenae and Metopolophium dirhodum.

The reproduction of apterous and alate morphs of the aphids Sitobion avenae and Metopolophium dirhodum is compared on the basis of fecundity in 5- and 10-day periods of adult life. Apterae of both species are consistently more fecund than alatae of comparable weight, producing about three more nymphs on average in any 5-day period. The reproductive differences are related to the number and quality of embryos at eclosion and to ovulation rates, both of which in turn appear to be linked to wing-muscle maintenance. These relationships between weight, embryos and reproduction may be used to predict a newly moulted adult aphid's fecundity, a method which may facilitate the assessment of resistance to aphids in new cereal varieties, by obviating lengthy recording of reproduction. The strategies by which alatae of these and other aphid species minimize the difference between their fecundity and that of apterae are discussed.

Age Factors↗
PubMed1998

Time to pregnancy and exposure to pesticides in Danish farmers. ASCLEPIOS Study Group.

OBJECTIVE: Circumstantial evidence suggests that organic farmers may have higher sperm count than other men, but comprehensive epidemiological studies of male fecundity among farmers have never been carried out. A substantial increase of sperm count is expected to translate into a shorter time to pregnancy--the number of menstrual cycles or months it takes a couple to get pregnant from discontinuation of birth control. Toxicological effects on spermatogenesis in humans and animals have been described after exposure to several pesticides. The aim of this study was to examine time to pregnancy among farmers who used pesticides (traditional farmers) and farmers who did not (organic farmers). METHODS: A total of 904 (84%) men, selected from the Danish Ministry of Agriculture lists of traditional and organic farmers, participated in telephone interviews. Information was collected on time to pregnancy for the youngest child, exposure to pesticides, and potential confounders. RESULTS: With the discrete analogue of the Cox regression model (including potential confounders: male and female smoking, female age, parity, and contraceptive method), the fecundability ratio between traditional farmers who used pesticides and organic farmers was 1.03 (95% confidence interval (95% CI) 0.75 to 1.40). In the group of farmers who sprayed with pesticides, none of the characteristics related to the use of pesticides could account for the variation in time to pregnancy. CONCLUSIONS: No overall effect of pesticides on male fecundability was found in this retrospective study among Danish farmers. Also, we found no evidence of higher male fecundability in organic farmers.

Adolescent↗
PubMed1999

Exposure to toluene in the printing industry is associated with subfecundity in women but not in men.

OBJECTIVE: To examine the possible influence of exposure to toluene on human fertility. METHODS: In a cross sectional study, a sample of 150 male and 90 female printing industry workers were interviewed retrospectively on reproductive experience with a modified version of the European study of infertility and subfecundity questionnaire. Exposure categories comprised job descriptions and information on exposure measurements obtained by industrial hygienists. The fecundability ratio (FR) was estimated on the basis of time to pregnancy (TTP) or periods of unprotected intercourse not leading to pregnancy (PUNP) by means of survival analysis with proportional hazard models. Confounders such as age, ethnicity, smoking, parity, pelvic inflammatory diseases, and frequency of sexual intercourse were controlled for in the analyses. RESULTS: 256 Periods of TTP or PUNP were reported by men and 174 by women. After exclusion of induced abortions, birth control failures, and periods without employment for female workers we were able to analyse 169 periods in men and 100 periods in women. Male workers who had been exposed to different concentrations of toluene and their partners did not show a reduction in fecundity. In women (39 periods occurred during exposure) fecundity was reduced (FR 0.47, 95% confidence interval (95% CI) 0.29 to 0.77). Neither, restriction to only the first period nor exclusion of PUNPs changed the results (FR 0.48, 95% CI 0.24 to 0.97). CONCLUSION: After considering possible biases, low daily exposure to toluene in women seems to be associated with reduced fecundity. This result is in accordance with other findings for organic solvents and supports both the hypotheses that (a) organic solvents could affect hormonal regulation, and that (b) organic solvents increase early fetal losses which in turn contributes to longer times of unprotected intercourse.

Adolescent↗
PubMed2003

Shift work and subfecundity: a causal link or an artefact?

AIMS: The Danish National Birth Cohort (DNBC) was used to examine whether shift work is associated with reduced fecundity as estimated by time to pregnancy (TTP). METHODS: From 1 March 1998 to 1 May 2000, 39 913 pregnant women were enrolled in the DNBC. Data on job characteristics and TTP (0-2, 3-5, 6-12, and >12 months) were used for 17 531 daytime workers and 3907 shift workers who had planned the pregnancy. Fecundity odds ratios (ORs) were calculated with 95% confidence intervals using the discrete time survival analysis techniques performed by logistic regression. An OR above 1 expresses a shorter TTP and then a higher fecundity. Potential confounders, such as age at conception, gravidity, prepregnant body mass index, smoking, and alcohol consumption, as well as occupational characteristics, were also included in the model. RESULTS: Fixed evening workers and fixed night workers had a longer TTP. Compared with daytime workers, the adjusted ORs were 0.80 (95% CI 0.70 to 0.92) for fixed evening workers, 0.80 (95% CI 0.63 to 1.00) for fixed night workers, 0.99 (95% CI 0.91 to 1.07) for rotating shift (without night) workers, and 1.05 (95% CI 0.97 to 1.14) for rotating shift (with night) workers. When analysis was restricted to nulliparous women, the estimates remained unchanged. The proportions of unplanned pregnancies and contraceptive failures were higher among fixed evening and fixed night workers. CONCLUSIONS: There was no unequivocal evidence of a causal association between shift work and subfecundity. The slightly reduced fecundity among fixed evening workers and fixed night workers may be mediated by pregnancy planning bias or differential options for sexual contacts.

Circadian Rhythm↗
PubMed1999

Fertility potential of individual sperm donors.

OBJECTIVE: To study the fertility potential of individual semen donors with ejaculates of optimal as compared to suboptimal quality. METHODS: 363 semen donations were obtained from 11 donors between January 1993 and September 1997. 270 samples were cryopreserved and 1,399 straws obtained from 120 ejaculates were used in 495 insemination cycles. RESULTS: 52 pregnancies were achieved in 128 recipients (40.6%). No significant differences were found between donors of high fecundability and those of low fecundability regarding sperm parameters. The mean donor fecundability index was 10.5%. The optimal and suboptimal samples yielded similar results. Donors with suboptimal semen quality had an increased number of samples rejected after thawing. CONCLUSION: Traditional semen analysis parameters do not differentiate high from low fecundability donors. Suboptimal results of the semen analysis should not exclude potential donors from an artificial insemination donor (AID) program.

Cryopreservation↗
PubMed2006

Environmental stress and reproduction in Drosophila melanogaster: starvation resistance, ovariole numbers and early age egg production.

BACKGROUND: The Y model of resource allocation predicts a tradeoff between reproduction and survival. Environmental stress could affect a tradeoff between reproduction and survival, but the physiological mechanisms underlying environmental mediation of the tradeoff are largely unknown. One example is the tradeoff between starvation resistance and early fecundity. One goal of the present study was to determine if reduced early age fecundity was indeed a robust indirect response to selection for starvation resistance, by investigation of a set of D. melanogaster starvation selected lines which had not previously been characterized for age specific egg production. Another goal of the present study was to investigate a possible relationship between ovariole number and starvation resistance. Ovariole number is correlated with maximum daily fecundity in outbred D. melanogaster. Thus, one might expect that a negative genetic correlation between starvation resistance and early fecundity would be accompanied by a decrease in ovariole number. RESULTS: Selection for early age female starvation resistance favored survival under food deprivation conditions apparently at the expense of early age egg production. The total number of eggs produced by females from selected and control lines was approximately the same for the first 26 days of life, but the timing of egg production differed such that selected females produced fewer eggs early in adult life. Females from lines selected for female starvation resistance exhibited a greater number of ovarioles than did unselected lines. Moreover, maternal starvation resulted in progeny with a greater number of ovarioles in both selected and unselected lines. CONCLUSION: Reduced early age egg production is a robust response to laboratory selection for starvation survival. Ovariole numbers increased in response to selection for female starvation resistance indicating that ovariole number does not account for reduced early age egg production. Further, ovariole number increased in a parallel response to maternal starvation, suggesting an evolutionary association between maternal environment and the reproductive system of female progeny.

Animals↗
PubMed1990

Fitness and its components in Drosophila melanogaster.

Fitness and its components in Drosophila melanogaster were estimated under the homozygous condition. All of these parameters, except for egg-to-adult viability and female fecundity, were measured under interspecific competition with D. hydei. The following results were obtained: (1) Significant genetic variation was detected in fitness, productivity, adult viability, total egg-to-adult viability and female fecundity. (2) Significant correlation was obtained between fitness and productivity (rp = 0.792 for phenotypic correlation, rg = 0.945 for genotypic correlation), between fitness and total egg-to-adult viability (rp = 0.355, rg = 0.395), and between fitness and female fecundity (rp = 0.451, rg = 0.511). (3) There was no significant correlation between total egg-to-adult viability and fecundity (rp = -0.046). The biological implications of the interrelationship between fitness and its components are discussed.

Animals↗
PubMed2004

Polyandry, life-history trade-offs and the evolution of imprinting at Mendelian loci.

Genomic imprinting causes parental origin-dependent differential expression of a small number of genes in mammalian and angiosperm plant embryos, resulting in non-Mendelian inheritance of phenotypic traits. The "conflict" theory of the evolution of imprinting proposes that reduced genetic relatedness of paternally, relative to maternally, derived alleles in offspring of polygamous females supports parental sex-specific selection at gene loci that influence maternal investment. While the theory's physiological predictions are well supported by observation, the requirement of polyandry in the evolution of imprinting from an ancestral Mendelian state has not been comprehensively analyzed. Here, we use diallelic models to examine the influence of various degrees of polyandry on the evolution of both Mendelian and imprinted autosomal gene loci that influence trade-offs between maternal fecundity and offspring viability. We show that, given a plausible assumption on the physiological relationship between maternal fecundity and offspring viability, low levels of polyandry are sufficient to reinforce exclusively the fixation of "greedy" paternally imprinted alleles that increase offspring viability at the expense of maternal fecundity and "thrifty" maternally imprinted alleles of opposite effect. We also show that, for all levels of polyandry, Mendelian alleles at genetic loci that influence the trade-off between maternal fecundity and offspring viability reach an evolutionary stable state, whereas pairs of reciprocally imprinted alleles do not.

Biological Evolution↗
PubMed2006

Evolution under relaxed sexual conflict in the bulb mite Rhizoglyphus robini.

The experimental evolution under different levels of sexual conflict have been used to demonstrate antagonistic coevolution in muscids, but among other taxa a similar approach has not been employed. Here, we describe the results of 37 generations of evolution under either experimentally enforced monogamy or polygamy in the bulb mite Rhizoglyphus robini. Three replicates were maintained for each treatment. Monogamy makes male and female interests congruent; thus selection is expected to decrease harmfulness of males to their partners. Our results were consistent with this prediction in that females from monogamous lines achieved lower fecundity when housed with males from polygamous lines. Fecundity of polygamous females was not affected by mating system under which their partners evolved, which suggests that they were more resistant to male-induced harm. As predicted by the antagonistic coevolution hypothesis, the decrease in harmfulness of monogamous males was accompanied by a decline in reproductive competitiveness. In contrast, female fecundity and embryonic viability, which were not expected to be correlated with male harmfulness, did not differ between monogamous and polygamous lines. None of the fitness components assayed differed between individuals obtained from crosses between parents from the same line and those obtained from crosses between parents from different lines within the same mating system. This indicates that inbreeding depression did not confound our results. However, interpretation of our results is complicated by the fact that both males and females from monogamous lines evolved smaller body size compared to individuals from polygamous lines. Although a decrease in reproductive performance of males from monogamous lines was still significant when body size was taken into account, we were not able to separate the effects of male body size and mating system in their influence on fecundity of their female partners.

Animals↗
PubMed2000

Tebufenozide targeted against codling moth (Lepidoptera: Tortricidae) adults, eggs, and larvae.

The effectiveness of tebufenozide applied against the adult, egg, and larvae of codling moth, Cydia pomonella (L.), was evaluated. Significant reductions in fecundity and egg hatch occurred after 1-h and 24-h exposures of females and 24-h exposures of males-only to residues in plastic plates. A significant reduction in egg hatch was also found after a 1-h exposure of males. The ovicidal effects of tebufenozide in field trials did not significantly differ for eggs laid on residues or treated topically. Corrected egg mortality exceeded 95% for cohorts laid <130 degree-days after sprays were applied. Fecundity and egg hatch were measured after either a 24-h exposure of moths or a 10-d exposure of moths and eggs on apple trees. Significant reductions in both fecundity and fertility occurred compared with an untreated control up to 7 d in the 24-h assays and accounted for 60-70% fewer larvae produced per mated female. The mean numbers of larvae produced per mated female after the 10-d exposure were reduced 100-75% in assays started on day 0-21 after the spray application compared with the untreated control. Fecundity was significantly reduced for 7 d and egg hatch was reduced for the entire 21-d test period in these trials. Residues had a 14-d half-life on apple foliage. Residues applied to foliage or to foliage and fruit did not significantly increase the proportion of uninjured fruit compared with the untreated control in bioassays where neonates were placed on foliage 10 cm from fruit. However, the proportion of injured fruits with shallow stings versus deep entries was higher on the treated versus the untreated plants. Field applications of tebufenozide reduced fruit injury >90% when applied early during emergence. Plots treated after the beginning of egg hatch had a larger proportion of injured fruits with shallow larval feeding.

Animals↗
PubMed2006

Time to pregnancy among female greenhouse workers.

OBJECTIVES: Female greenhouse workers, who constitute a major occupational group exposed to pesticides at childbearing age, were studied to measure the effects of pesticide exposure on time to pregnancy. METHODS: Data were collected through postal questionnaires with detailed questions on time to pregnancy, lifestyle factors (eg, smoking habits, coffee and alcohol consumption), and worktasks (eg, application of pesticides, re-entry activities, and workhours) of the respondents and their partners in a 6-month period prior to conception of the most recent pregnancy. The relation between time to pregnancy and exposure to pesticides among 398 female greenhouse workers and 524 referents was studied in a Cox's proportional hazards model. RESULTS: The crude fecundability ratio for female greenhouse workers versus the reference group was 1.18 [95% confidence interval (95% CI) 1.03-1.35], but correction for confounding changed the fecundability ratio to 1.11 (95% CI 0.96-1.29). An evaluation of specific biases for time-to-pregnancy studies showed that these results were biased by the reproductively unhealthy worker effect. Restricting the analyses to full-time workers or first pregnancies only resulted in an adjusted fecundability ratio of 0.89 (95% CI 0.67-1.19) and 0.90 (95% CI 0.62-1.32), respectively. Among the primigravidous greenhouse workers, an association was observed between prolonged time to pregnancy and gathering flowers (fecundability ratio 0.46, 95% CI 0.18-1.19). CONCLUSIONS: This study may offer some evidence for the hypothesis of adverse effects of pesticide exposure on time to pregnancy, but more research is needed to elucidate these effects.

Adult↗
PubMed2005

Time to pregnancy among Danish laboratory technicians who were a part of the National Birth Cohort.

OBJECTIVES: The Danish National Birth Cohort was used to examine whether laboratory work was associated with reduced fecundity. METHODS: Self-reported data on laboratory work and waiting time to pregnancy (0-2, 3-5, 6-12 and > 12 months) were used for 829 female laboratory technicians interviewed in 1997-2003. Altogether 6250 female teachers formed the reference group. A discrete-time survival analysis with a complementary log-log link was applied to estimate the fecundability ratio between the exposed and unexposed women, with adjustment for maternal age, gravidity, smoking, prepregnancy body mass index, and paternal job. RESULTS: No difference in time to pregnancy was found between the laboratory technicians and teachers or between the laboratory technicians with different exposures. The adjusted fecundability ratio for the laboratory technicians was 0.94 [95% confidence interval (95% CI) 0.86-1.02] for all pregnancies and 0.98 (95% CI 0.86-1.13) for first pregnancies. A healthy worker effect was found for the laboratory technicians working with the work processes under study. CONCLUSIONS: The results do not suggest that laboratory work in Denmark at present impairs female fecundity.

Adult↗
PubMed1999

The effect of pesticide exposure on time to pregnancy.

The Ontario Farm Family Health Study provided data for examination of the effects of pesticide exposure on time to pregnancy. In this retrospective cohort study of farm couples in Ontario, Canada, the farm operator, husband, and wife completed questionnaires during 1991-1992. We asked about pesticides used on the farm and pesticide activities of the husband and wife for each month of trying to conceive. After exclusions, 2,012 planned pregnancies remained for analysis. We used an analog of the Cox proportional hazards model to calculate conditional fecundability ratios (conditional on pregnancy). There was no strong or consistent pattern of associations of pesticide exposure with time to pregnancy. During exposure intervals in which women participated in pesticide activities (during most of which the men also participated), however, 6 of 13 pesticide exposure categories were associated with a decrease in fecundability (conditional fecundability ratio range = 0.51-0.80). For exposure intervals in which only the men participated in pesticide activities or in which neither men nor women participated in pesticide activities but pesticides had been used on the farm, conditional fecundability ratios ranged from 0.75 to 1.50, with no apparent consistency among pesticide classes, chemical families, or active ingredients.

Agriculture↗
PubMed1999

Design options and sources of bias in time-to-pregnancy studies.

Studies of fecundity are few, and there is a need to know how fecundity develops over time and to identify its determinants. Since fecundity is best measured by studying time to pregnancy, valid and well-recognized instruments are needed for data collection. A standardized questionnaire on fecundity not only has to obtain information on waiting time, but also information on the importance of evaluation results. The use of contraceptive methods, the understanding of family planning, and behavioral changes driven by past reproductive experience are issues of importance for designing and interpreting results, as are other sources of bias also.

Bias↗
PubMedDate not supplied

[The fertility of thorny-headed worms in the genus Echinorhynchus (Acanthocephala: Echinorhynchidae) from Lake Baikal].

The total number of eggs (absolute fecundity) and the number of eggs per 1 gr of body weight (relative fecundity) of Echinorhynchus borealis Linstow, 1901, E. salmonis salmonis Muller, 1784, E. s. baicalensis Bogolepova, 1957 and E. truttae Schrank, 1788 from the Baikal lake was examinide. The absolute fecundity decreases in the row or species: E. borealis (26,200 eggs), E. s. salmonis (110,113), E. truttae (8123), E. s. baicalensis (6087). The fecundity of acanthocephalans depends on the host species. The dependence of the whole number of larvae upon the body length of females (r = 0.804) is shown.

Acanthocephala↗