Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Fecundability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1991

The regulation of mortality and fecundity in Schistosoma mattheei following a single experimental infection in sheep.

The regulation of mortality and fecundity of Schistosoma mattheei in sheep was examined using a series of mathematical models applied to data culled from the literature. Parasite mortality (mu) was found to be an increasing linear function of the magnitude of the initial infection over the ranges of doses examined (200-91,000 cercariae) where mu = 9.78 x 10(-3) + 3.476 x 10(-7) infection dose. Parasite fecundity (lambda) was found to be inversely related to the duration of the infection. The best fit model for parasite fecundity was one in which fecundity decreased exponentially with time since initial infection, lambda = lambda 0e-delta(t-tau). There was no evidence for density-dependent regulation of fecundity.

Animals↗
PubMed1991

A comparative analysis of the cycle fecundity rates associated with combined human menopausal gonadotropin (hMG) and intrauterine insemination (IUI) versus either hMG or IUI alone.

Human menopausal gonadotropin (hMG) superovulation combined with washed intrauterine insemination (IUI) has been advocated for the treatment of various forms of infertility when more traditional therapy has failed. To assess the relative efficacy of combined treatment with hMG and IUI compared with either hMG or IUI alone, pregnancy outcomes of the three treatment groups were compared in couples having infertility because of male factor, cervical factor, endometriosis, or unexplained. A total of 751 cycles were analyzed from 322 couples. The mean cycle fecundity rate associated with hMG/IUI therapy was significantly higher than either hMG or IUI therapy alone for all patients (hMG/IUI = 19.6%, hMG = 6.3%, IUI = 3.4%). The improvement in cycle fecundity rates with hMG/IUI therapy was also observed when the couples were separated by infertility diagnostic groups: male factor (hMG/IUI = 15.3%, hMG = 4.4%, IUI = 3.0%), cervical factor (hMG/IUI = 26.3%, hMG = 7.9%, IUI = 5.1%), endometriosis (hMG/IUI = 12.85%, hMG = 6.6%), and unexplained infertility (hMG/IUI = 32.6%, hMG = 5.5%, IUI = 0%). Moreover, in patients who had failed to conceive with hMG or IUI alone, the cycle fecundity rate when they were switched to hMG/IUI therapy equaled that of patients who received combined therapy from the onset. We conclude that cycle fecundity rates and cumulative pregnancy rates are significantly greater using a combination of hMG and IUI compared with either modality alone in the treatment of male factor, cervical factor, endometriosis, or unexplained infertility. Indeed, in couples with nontubal related infertility, cycle fecundity rates with hMG/IUI approach the rates seen with in vitro fertilization and gamete intrafallopian tube transfer.

Endometriosis↗
PubMed1996

Projections of impaired fecundity among women in the United States: 1995 to 2020.

OBJECTIVE: To determine the number of women aged 15 to 44 years with impaired fecundity every 5 years from 1995 to 2020. DESIGN: Data are used from cycle IV of the National Survey of Family Growth conducted by the National Center for Health Statistics. Population projections prepared by the U.S. Census Bureau are used for the expected population base for 1995 to 2020. Prospective demographic projection analysis is used to estimate the number of women with impaired fecundity. PARTICIPANTS: The National Survey of Family Growth interviewed 8,450 women aged 15 to 44 years as of March 15, 1988. MAIN OUTCOME MEASURE: Number of women with impaired fecundity. RESULTS: The number of women with impaired fecundity may drop from 5.1 million in 1995 to 4.7 million in 2015 and then rise to 4.8 to 5.9 million in 2020. CONCLUSION: The age structure of the population will cause the absolute number of women with impaired fecundity in the United States to increase slowly, if at all, over the next 25 years.

Adolescent↗
PubMed1992

The mortality and fecundity of Haemonchus contortus in parasite-naive and parasite-exposed sheep following single experimental infections.

Parasite-exposed lambs and their parasite-naive controls were experimentally infected once only with 30,000 H. contortus larvae at 3, 9, 12, and 20 weeks following termination of a moderate immunizing infection of 30,000 H. contortus larvae. Previously exposed lambs, challenged at 3 weeks, had a significant reduction in the total H. contortus worm burden as compared to parasite-naive controls. No difference in the total H. contortus worm burden was found between parasite-exposed or parasite-naive lambs challenged at 9 weeks or thereafter. Female worms were found to be significantly smaller in lambs previously exposed to the parasite as compared to those found in parasite-naive lambs. The average parasite fecundity was 4700 eggs per female worm per day. Previous exposure of the lambs to the parasite had no effect on parasite fecundity. Various mathematical models were used to examine parasite fecundity. Parasite fecundity was found to increase in the initial post-challenge period reaching a constant value approximately 58 days after challenge infection. No density-dependent constraints on fecundity were observed.

Animals↗
PubMed1998

Declining fecundity and ovarian ageing in natural fertility populations.

Worldwide, human fertility declines with increasing maternal age, after contraceptive-use patterns and behavioral factors are taken into consideration. Here, we summarize some of our theoretical and empirical work examining the biological factors contributing to this age pattern of fertility. We undertook an 11 month prospective endocrinological study in a natural fertility (non-contracepting) population (rural Bangladesh) to estimate the contributions of fetal loss and fecundability (the probability of conception) to declining fecundity with age. Prospective interviews and urine samples for pregnancy tests were collected twice weekly from up to 700 women. These data were used to test mathematical models of the underlying biological processes contributing to changing fecundability and fetal loss risk with maternal age. The results indicate that much of the decline in fecundity can be attributed to an increasing risk of fetal loss with maternal age. Much of this fetal loss is due to chromosomal abnormalities--a result of ageing oocytes. Fecundability, on the other hand, does not begin to decline until the early 40s. We hypothesize that this is also a result of ageing at the ovarian level, namely follicular atresia, in the years just prior to menopause. The irregularity of menstrual cycles--longer cycles and increasingly variable hormonal patterns--at these ages may be a direct result of the small and rapidly dwindling remaining pool of follicles. We present a simple mathematical model of this process, and some preliminary laboratory results that support the model.

Adult↗
PubMed2003

The influence of malaria parasite genetic diversity and anaemia on mosquito feeding and fecundity.

Studies of invertebrate-parasite interactions frequently report that infection reduces host fecundity. The extent of the reduction is likely to be determined by a wide range of host and parasite factors. We conducted a laboratory experiment to evaluate the role of parasite genetics and infection genetic diversity on the fecundity of mosquitoes carrying malaria parasites. The malaria vector Anopheles stephensi was infected with either of 2 different genotypes of the rodent malaria parasite Plasmodium chabaudi, or by a mixture of both. Mixed genotype infections reduced mosquito fecundity by 20%, significantly more than either of the 2 single genotype infections. Mixed genotype infections were associated with high gametocyte densities and anaemia in mice, both of which were correlated with reduced bloodmeal size in mosquitoes. Bloodmeal size was the most important predictor of mosquito fecundity; the presence and number of parasites had no direct effect. Parasite density influenced the propensity of mosquitoes to feed on infected mice, with a higher percentage of mosquitoes taking a meal as asexual parasite and gametocyte density increased. Thus mosquitoes may preferentially feed on hosts who will most impair their fecundity.

Anemia↗
PubMed1999

Regulation of nematode fecundity in the ring-necked pheasant (Phasianus colchicus): not just density dependence.

Patterns of nematode fecundity were investigated for infections of the caecal worm Heterakis gallinarum in the ring-necked pheasant (Phasianus colchicus). Worm length was a good predictor of parasite fecundity. After controlling for worm length no other factors, including parasite intensity, were related to worm fecundity. Density dependence in worm size was detected in natural infections at parasite intensities above a threshold of 96 worms (worm size decreased with increasing parasite intensity). However, below this threshold, worm size actually decreased with decreasing parasite intensity (inverse density dependence). The interaction between density dependence and inverse density dependence in regulating the development and subsequent fecundity of H. gallinarum worms in ring-necked pheasants was demonstrated in an infection experiment. Density dependence was observed in the stunted growth of worms in heavily infected hosts, relative to worms in lightly infected hosts. Inverse density dependence in worm size was the common pattern across hosts by the end of the experiment, when parasite intensities were below the density dependence threshold. This is the first study to document both density dependence and inverse density dependence in parasite fecundity in the same host-helminth system.

Animals↗
PubMed2003

Inbreeding depression in fecundity and inbred line extinction in the bulb mite, Rhizoglyphus robini.

This study investigated the magnitude of inbreeding depression in fecundity, and whether the depression is purged during six generations of sib mating in the bulb mite, Rhizoglyphus robini. The progeny resulting from a single generation of brother-sister mating suffered significant inbreeding depression in fecundity. During the following six generations of continuous sib-mating, 58% lines were lost, 45% because of sterility and 13% because of preadult mortality. The lines were then outcrossed, and their inbreeding depression compared with that of the base population. The inbreeding depression for the outcrossed population was 0.15, and for the base population 0.19, but the difference was not significant. The lack of significant purging of inbreeding depression indicates that it was caused either by detrimental genes of small effect, or by the breaking down of overdominant relations between alleles. However, the large proportion of extinct lines points to the former mechanism as a predominant cause of inbreeding depression. Theory predicts that the probability of line extinction with inbreeding increases with its load of mutations. If phenotypic variation in fecundity was partly because of differences in numbers of mutations carried by individuals, the fecundity of the line founder could be expected to correlate with the probability that the line derived from it will survive long-term inbreeding. Indeed, fecundity of founder females was significantly associated with line survival, which suggests that line extinction rate may be used as a method to study individual mutational loads, for example, in studies of sexual selection.

Animals↗
PubMed2003

What fecundity patterns indicate about aging and longevity: insights from Drosophila studies.

The age pattern of fecundity is represented as a result of a superposition of two processes: the genetic fecundity program encoded in the organism's reproductive machinery and senescence of the reproductive system. Accumulation of oxidative damage produces the energy decline, which could potentially be used in reproduction. As a result, the age-declining process arises in the reproductive machinery at a critical age. We show that this mechanism is common for different species. It establishes a connection between the decline of organism vitality and reproductive senescence. We suggest a parametric description of a fecundity pattern that allows for prediction of reproductive longevity. We apply the approach to Drosophila studies to analyze the relation between fecundity and survival. We show that fecundity patterns may predict a mean life span in Drosophila under specified environmental conditions.

Aging↗
PubMed1997

Is fecundability associated with month of birth? An analysis of 19th and early 20th century family reconstitution data from The Netherlands.

The relationship between fecundability and month of birth was investigated in a cohort of 1526 women who married between 1802 and 1929, using only women whose first marriage occurred before the age of 35 years. On the basis of their time to pregnancy (TTP, calculated as time between wedding and first birth minus gestational length), women were categorized into two groups: fecunds (TTP up to 12 months or prenuptial conceptions, n = 1348) and subfecunds (TTP >18 months, n = 118). By use of logistic regression, cosinor functions with a period of 1 year or 6 months and variable shift and amplitude were fitted through the monthly odds of subfecunds versus fecunds. The best fitting curve was unimodal, with a zenith in September (P = 0.13 for H0: no differences). Exclusion of childless women (n = 36, minimum follow-up 5 years) from the subfecunds led to a similar curve (P < 0.01), while childless women, as compared with fecunds, showed a birth distribution that was best represented with a bimodal curve with zeniths in January and July (P = 0.06). This study provides evidence for the existence of differences in fecundability by month of birth. The cause of this relationship is unclear, but may lie in a melatonin-dependent circannual variability of the quality of the oocyte.

Female↗
PubMed1993

Fecundity and oviposition in laboratory colonies of the screwworm fly (Diptera: Calliphoridae).

The screwworm fly is mass-produced using an artificial larval diet and an artificial oviposition substrate. On the artificial diet, mean fecundity was 185 eggs per female, whereas host-reared flies averaged 280 eggs per female. Host-reared flies were generally larger (head capsule width [HCW] > 3.6 mm) than laboratory-reared flies (HCW < 3.6 mm). Larger flies are generally more fecund, and size is related to larval nutrition. Only 75-89% of females reared on artificial diet and maintained at 30 degrees C were gravid at 6 d of age compared with 100% of host-reared females tested at 5-6 d. When gravid females were offered artificial substrate for oviposition, approximately 28% failed to oviposit and another 11% laid only partial clutches. Among all females tested for oviposition, 25% of the total egg production was withheld. Fecundity influenced oviposition, because the more mature eggs a female had, the more likely she was to oviposit. Supplementing the adult diet of honey and water with raw meat increased fecundity by 14% under normal laboratory conditions, but by as much as 350% in flies in which larval feeding was curtailed by removal of the larvae from the media 1 d before the normal completion of development. Many females became gravid in 4-5 d at 30 degrees C versus 8-9 d at 22 degrees C. But fecundity and oviposition rate were more variable (less synchronous) in colonies maintained at the higher temperature. This suggests that there may be greater selection for laboratory adaptation at the higher maintenance temperatures.

Animals↗
PubMed2001

Is survivorship a better fitness surrogate than fecundity?

Although fitness depends on both survivorship and fecundity, we tend to assume fecundity relates to fitness more directly than survivorship. In fact, several recent ecological studies suggest fitness depends more heavily on annual survivorship than annual fecundity for most taxa with lifespans longer than one year. These studies review elasticities of transition matrices for a broad range of taxa. Elasticities covary monotonically with selection gradients for demographic rates and are identical to selection gradients for traits rescaled to have mean values of zero and variance of one. For all taxa except semelparous perennial plants, adult survivorship has consistently higher elasticity than other suites of demographic rates. Fecundity only rarely has the highest elasticity. Thus, differences in yearly survival affect fitness disproportionately more than differences in yearly fecundity, even in many exponentially growing populations. This pattern reinforces the importance of interpreting the contribution of vital rates to fitness in the context of life history and population dynamics.

Animals↗
PubMed1994

Effects of alcohol on blastocyst implantation and fecundity in the rat.

The effects of alcohol on blastocyst implantation and fecundity were determined. Pregnant rats (insemination = day 1) received vehicle only (water), or alcohol (2 or 4 g/kg body weight) daily by feeding tube on days 1-4 and the time of implantation determined on day 5 or fecundity assessed on day 19. Implantation sites were rendered visible by the blue-reaction; fecundity was expressed as the ratio of live fetuses to total implantations. The time course of blastocyst implantation was advanced by alcohol (2 g/kg dose). At 1000 hr, 1.9 vs. 0.9 blastocysts had implanted in treated vs. controls. By 1200 hr, 66 vs. 17% of blastocysts had implanted and by 1500 hr 90 vs. 52% had implanted in the 2 g/kg dose group vs. controls. Blastocyst implantation was not consistently advanced by the 4 g/kg dose of alcohol. The total number of blastocysts ultimately implanting did not differ between groups (control: 7.0 +/- 0.9; 2 g: 7.3 +/- 0.9; 4 g: 7.1 +/- 0.5 sites/cornu at 1800 hr). Fecundity did not differ markedly between control and the 2 g/kg dose group (97 vs. 96%, respectively), but was reduced in the 4 g/kg dose group (58%). The results indicate that daily administration of alcohol (2 g/kg body weight) during the preimplantation period (days 1-4) advances the time course of blastocyst implantation without reducing fecundity.

Alcohol Drinking↗
PubMed2000

The influence of male and female body size on copulation duration and fecundity in Drosophila melanogaster.

We studied two components of the mating system, copulation duration and early fecundity, in relation to body size in Drosophila melanogaster. Body size variation was created experimentally by varying the degree of crowding (starvation) among larvae from an inbred strain, keeping the genetics and temperature as constant as possible. Hence, in contrast to most previous studies, where genetic and environmental variation have been confounded, we aimed at investigating how much pure phenotypic variation could influence copulation duration and early fecundity. It is shown that copulation duration and fecundity both strongly dependent on female body size, but either not or much less so on male body size. Small females mate faster than medium or large females and small females have the lowest fecundity. Among males, medium-size males are more fecund than smaller or larger males, resulting in stabilising selection for intermediate male size. These results are in contrast with previous findings.

Animals↗
PubMed2002

Pupal mass and wing length as indicators of fecundity in Aedes albopictus and Aedes geniculatus (Diptera: Culicidae).

Many studies investigating the ecology and evolution of mosquitoes rely on morphometric measurements related to body size to estimate fecundity. Determining the most reliable estimators of fecundity is therefore an important methodological consideration. We compared the relative accuracy of pupal mass and wing length in predicting the fecundity (number of mature stage IV follicles of the first gonotrophic cycle) for (1) Aedes albopictus (Skuse) reared in the laboratory, (2) Aedes geniculatus (Oliver) reared in the laboratory, and (3) A. geniculatus that completed their larval development in water-filled tree holes (their natural habitat) in the field. In all cases, pupal weight and wing length provided highly significant and equally accurate indicators of fecundity. Furthermore, the measurement error (1 - repeatability) for both traits was < or = 1%. Our results indicate that either pupal mass or wing length can be used with confidence to predict fecundity in these two aedine mosquitoes.

Aedes↗
PubMed2000

The relationship between size and fecundity in Aedes albopictus.

Recent use of correlates of the intrinsic rate of increase and models to study population dynamics in mosquitoes has emphasized the need for species specific data on the relationship of morphological factors such as body size to life history parameters such as fecundity. Aedes albopictus is of concern because of its continued spread and population growth in the U.S. and the potential for virus transmission. We examined the relationships between pupal wet weight and adult female wing length and between female wing length and fecundity in the first gonotrophic cycle in U.S. strains of Ae. albopictus. There was a significant positive relationship between pupal wet weight and adult wing length. The relationship between wing length and fecundity was also significant and positive, but with lower correlation coefficients and higher variance indicating that other factors also affect fecundity. The regression coefficients for the fecundity-wing length equation did not differ between two strains of Ae. albopictus.

Aedes↗
PubMed1992

Abnormal findings on hysterosalpingography: effects on fecundity in a donor insemination program using frozen semen.

OBJECTIVE: We sought to evaluate the effect of abnormal baseline hysterosalpingography (HSG) on subsequent fecundity during the first six cycles of treatment. METHODS: Hysterosalpingography was performed on 208 asymptomatic ovulatory women with no history of pelvic disease who were referred for donor insemination. The findings were categorized into five groups: 1) normal study, 2) uterine anomaly or filling defect with bilateral tubal patency, 3) normal uterine anatomy with unilateral tubal patency, 4) normal uterine anatomy with bilateral tubal blockage, and 5) normal uterine anatomy with hydrosalpinx. Subjects in groups 4 and 5 received inseminations only if patency of at least one fallopian tube was demonstrated with laparoscopy. Life-table analysis was performed to calculate the average monthly fecundity and cumulative conception rates for each group. The Mantel-Haenszel test was used to compare group fecundities. RESULTS: A total of 1460 donor insemination cycles were performed. The number of cycles in each group were as follows: group 1, 1173 (80%); group 2, 153 (10%); group 3, 90 (6.2%); group 4, 16 (1.1%); and group 5, 28 (1.9%). None of the patients in group 4 or 5 conceived. The cumulative conception rates in the first three groups were 46, 34, and 40%, respectively, and were not significantly different from one another (P greater than .05). Although a high incidence of uterine filling defects and unilateral tubal blockage was observed (19.2%), the incidence of an abnormal HSG finding that significantly decreased fecundity was only 2.8%. CONCLUSION: In women with no history of tubal or uterine disease, routine HSG before initiation of donor insemination is of limited value for identifying decreased treatment fecundity.

Adult↗
PubMed1992

Relationship of follicle number and other factors to fecundability and multiple pregnancy in clomiphene citrate-induced intrauterine insemination cycles.

OBJECTIVE: To determine characteristics associated with pregnancy and multiple gestation after clomiphene citrate (CC)-intrauterine insemination (IUI). DESIGN: Prospective study of all patients undergoing CC-IUI between January 1, 1983 and December 31, 1989. SETTING: Private fertility clinic. PATIENTS: Eight hundred forty-nine patients undergoing 1,974 cycles of CC-IUI. MAIN OUTCOME MEASURES: Relationship between number and size of preovulatory follicles, age, additional infertility diagnosis, medication, and initial semen quality to fecundity, birth, and multiple gestation. RESULTS: Uncorrected, per cycle fecundity was 7.2%. The number of follicles greater than or equal to 12 mm (r = 0.055, P less than 0.05) was and the number greater than or equal to 15, 18, and 21 mm was not correlated with fecundity. Endometriosis with (P = 0.013) or without (P less than 0.0005) tubal adhesions and tubal adhesions alone (P = 0.005), decreased fecundability by 50%. Initial semen quality did not affect fecundity, unless semen concentration was less than 5 x 10(6)/mL or motility was less than 20%. Multiple pregnancy was not associated with the dose of CC, use of human chorionic gonadotropin, or number of follicles. CONCLUSIONS: Multiple pregnancy was unrelated to follicle numbers or to CC dose. The highest birth rates after CC-IUI occurred when initial sperm concentration was greater than or equal to 5 x 10(6)/mL, motility was greater than or equal to 20%, and no endometriosis or adhesions were present.

Clomiphene↗