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PubMed1994

A multistate model of fecundability and sterility.

This paper develops a multistate hazards model for estimating fecundability and sterility from data on waiting times to conception. Important features of the model include separate sterile and nonsterile states, a distinction between preexisting sterility and sterility that begins after initiation of exposure, and log-normally distributed fecundability among nonsterile couples. Application of the model to data on first birth intervals from Taiwan, Sri Lanka, and the Amish shows that heterogeneity in fecundability is statistically significant at most ages, but that preexisting sterility and new sterility are unimportant before age 40. These results suggest that sterility may not be an important determinant of natural fertility until later reproductive ages.

Adolescent↗

PubMed1993

Hutterite fecundability by age and parity: strategies for frailty modeling of event histories.

Effective fecundability declines with age and parity. Furthermore, women differ in their effective fecundability: some women have persistently low or high monthly chances of live-birth conception. Estimates are presented concerning the magnitude of these effects in a natural-fertility population: 406 Hutterite women in North America who had 3,206 births, largely in the 1940s and 1950s. The estimates are based on models that incorporate the effects of persistent heterogeneity and that use the full information provided by multiple-spell duration data. In addition, hazards rather than probabilities are modeled, piecewise linear hazard functions are used, and age and parity effects are decomposed systematically. These methods permit the development of more elaborate models of changing fecundability and of heterogeneity in postpartum amenorrhea.

Adolescent↗

PubMed1998

Fecundability of female twins.

Animal studies have shown evidence of prenatal hormonal interaction between unlike sexed fetuses, including reduced fertility among females. We evaluated whether the fecundability of female twins is different from that of singletons and whether it differs according to the sex of the co-twin. The study was based on a questionnaire survey of 12,681 female twins born in the period 1953-1976 and an interview survey of 760 female controls born in the period 1953-1966, both in Denmark. Outcome of the first try ever to become pregnant (pregnant, still trying, stopped trying, pregnant despite contraception, and never tried) and the waiting time to pregnancy distribution did not differ among monozygotic, dizygotic same sexed, and dizygotic unlike sexed twins. More twins had a waiting time of less than 2 months, compared with singletons. This difference probably reflects an artifact due to the data collection method, because it disappeared when the cutoff point was changed to include 2 months for singletons, and we found no difference for longer waiting times. Hence, we found no increase in fecundability for twins compared with singletons, nor any reduced fecundability among female twins from unlike sexed pairs.

Adolescent↗

PubMedDate not supplied

Female fecundity in highland Papua New Guinea.

Demographers often assume that interpopulation variation in birth spacing is attributable primarily to behavioral differences (e.g., in breastfeeding, coital frequency, or contraceptive practice), and that the contribution of physiological factors is negligible. This assumption may be correct, but it should be tested, especially in light of recent evidence that there may be more variation in ovarian function among human populations than was previously believed. In this paper, we apply a stochastic model of the determinants of fecundability (the monthly probability of conception) to endocrinological data collected among the Gainj, a tribal population in highland Papua New Guinea. Based on previous research, the Gainj are known to have age patterns of ovarian function that differ markedly from the Western norms. When account is taken of the late menarche, early menopause, and long ovarian cycles that appear to characterize Gainj women, mean apparent fecundability across the female reproductive span is reduced by about 27 per cent (from 0.316 to 0.235), and the mean waiting time to next apparent conception is increased by just over one month. Thus, despite the fact that Gainj women differ from Western women with respect to reproductive physiology by as much as or more than any other known population, the demographic impact of these differences appears to be slight.

Birth Intervals↗

PubMed1989

Do women with childhood exposure to cigarette smoking have increased fecundability?

The authors earlier conducted a retrospective study of time to pregnancy among a group of pregnant women in Minnesota, in order to investigate the relation between cigarette smoking and fecundability. Further analysis of these data shows that women who had been exposed as children to cigarette smokers had increased fertility. This finding lacks biologic plausibility. However, the authors found a similar association in a group of North Carolina women whose fecundability had been measured prospectively. Furthermore, both groups showed an apparent dose-response effect. The authors briefly describe this unexpected finding so that it might be more fully explored in other studies.

Fathers↗

PubMedDate not supplied

Estimation of fecundability from survey data.

The estimation of fecundability from survey data is plagued by methodological problems such as misreporting of dates of birth and marriage and the occurrence of premarital exposure to the risk of conception. Nevertheless, estimates of fecundability from World Fertility Survey data for women married in recent years appear to be plausible for most of the surveys analyzed here and are quite consistent with estimates reported in earlier studies. The estimates presented in this article are all derived from the first interval, the interval between marriage or consensual union and the first live birth conception.

Actuarial Analysis↗

PubMed1998

Fecundity in Thai and European regions: results based on waiting time to pregnancy.

Very little is known about the frequency of subfecundity in different cultures, ethnic groups and regions. To fill this gap, the European Study Group on Infertility and Subfecundity established data on the prevalence of infertility and subfecundity in five European regions. In this study, a comparison of fecundity was made between 4035 Caucasian women from five European countries and 1496 Asian women from southern Thailand. Fecundity was measured using 'time to pregnancy', i.e. the time women took to conceive after stopping contraceptive methods. The Thai primigravid women had a shorter time to pregnancy than European women, whereas time to pregnancy was found to be longer among Thai multigravidae, although this was not statistically significant. This study has illustrated that cross-culture comparison of subfecundity is difficult despite using a common protocol and questionnaire because of differences in the use of contraceptive methods and a different concept of pregnancy planning. The distribution of time to pregnancy for the Thai women was not outside the variation found within the European samples.

Adult↗

PubMed1991

Delaying childbearing: effect of age on fecundity and outcome of pregnancy.

OBJECTIVES: To study the age of the start of the fall (critical age) in fecundity; the probability of a pregnancy leading to a healthy baby taking into account the age of the woman; and, combining these results, to determine the age dependent probability of getting a healthy baby. DESIGN: Cohort study of all women who had entered a donor insemination programme. SETTING: Two fertility clinics serving a large part of The Netherlands. SUBJECTS: Of 1637 women attending for artificial insemination 751 fulfilled the selection criteria, being married to an azoospermic husband and nulliparous and never having received donor insemination before. MAIN OUTCOME MEASURES: The number of cycles before pregnancy (a positive pregnancy test result) or stopping treatment; and result of the pregnancy (successful outcome). RESULTS: Of the 751 women, 555 became pregnant and 461 had healthy babies. The fall in fecundity was estimated to start at around 31 years (critical age); after 12 cycles the probability of pregnancy in a woman aged greater than 31 was 0.54 compared with 0.74 in a woman aged 20.31. After 24 cycles this difference had decreased (probability of conception 0.75 in women greater than 31 and 0.85 in women 20.31). The probability of having a healthy baby also decreased--by 3.5% a year after the age of 30. Combining both these age effects, the chance of a woman aged 35 having a healthy baby was about half that of a woman aged 25. CONCLUSION: After the age of 31 the probability of conception falls rapidly, but this can be partly compensated for by continuing insemination for more cycles. In addition, the probability of an adverse pregnancy outcome starts to increase at about the same age.

Adult↗

PubMed1999

Potential for bias in estimating human fecundability parameters: a comparison of statistical models.

Fecundability studies, where couples attempting pregnancy subject to 'failure' (conception) one time in each menstrual cycle, present a natural discrete failure-time scenario. Because the biologic capacity to conceive varies among couples in the population, a complication arises in choosing a method of analysis, related to the fact that the maximum follow-up time can vary from study to study, and follow-up time could potentially have different effects on parameters based on different approaches to modelling. Traditional development in fertility studies has been based on an implicit assumption that binary outcomes for different menstrual cycles are mutually independent. We contrast traditional models to a random effects model where cycle viability is modelled as subject-specific. We clarify the interpretations for different parameters from different models. We show that the traditional approach yields some regression parameters that depend on follow-up time, limiting the generalizability of inferences based on this analytic approach. By contrast, the subject-specific model consistently estimates parameters of interest, if the underlying distribution is properly specified. Data from a fecundability study carried out in North Carolina serves to illustrate these points.

Bias↗

PubMed1995

Reduced fecundity in male ALS gene-carriers.

In order to study genetic aspects in multicase families, 89 amyotrophic lateral sclerosis (ALS) and 214 Parkinson disease (PD) kindreds were analyzed in parallel studies. Obligate gene-carriers were identified as described previously [Chatkupt et al., 1992: Am J Med Genet 44:508-512]. There were fewer children per gene-carrier male (2.42) than per gene-carrier female (3.25, Student's t-test, P < .0003) for ALS but not for other diseases. The data taken together suggest that fecundity in ALS gene-carriers was reduced in males, possibly as a result of reduced fertility. Since childbearing is usually accomplished well before the onset of neurological symptoms in ALS, and since reduced fecundity was found in male ALS gene-carriers, these findings raise the possibility that an ALS gene might have a pleiotrophic effect on fertility in males occurring decades before the onset of neurological symptoms. Evidence is presented linking reactive oxygen species to reduced fertility in males. Alternatively, decreased or nonfunctional androgen receptors could play a role.

Amyotrophic Lateral Sclerosis↗

PubMed2003

Blocking of malaria parasite development in mosquito and fecundity reduction by midgut antibodies in Anopheles stephensi (Diptera: Culicidae).

Rabbits were immunized three times with extracts of Anopheles stephensi midgut. Immunized rabbits showed a high titer of antibodies when characterized by ELISA. We investigated the effect of anti-mosquito midgut antibodies on mosquito fecundity, longevity, mortality, engorgement, and the development of the malaria parasite in mosquitoes. Fecundity was reduced significantly (38%) and similarly hatchability by about 43.5%. There was no statistically significant effect on mortality, longevity, and engorgement. When the mosquito blood meal contained anti-midgut antibodies, fewer oocysts of Plasmodium vivax developed in the mosquito midgut and the proportion of mosquitoes becoming infected was significantly reduced. We also found that the midgut antibodies inhibit the development and/or translocation of the sporozoites. Antisera raised against midgut of A. stephensi recognized eight polypeptides (110, 92, 70, 45, 38, 29, 15, 13 kDa) by Western blotting. Cross-reactive antigens/epitopes present in other tissues of A. stephensi were also examined both by Western blotting and in vivo ELISA. Together, these observations open an avenue for research toward the development of a vector-based malaria parasite transmission blocking vaccine and/or anti-mosquito vaccine.

Animals↗

PubMed1993

Fecundity before disease onset in women with rheumatoid arthritis.

OBJECTIVE: To examine fecundity prior to disease onset in women with rheumatoid arthritis (RA). METHODS: Two hundred fifty-nine RA patients with an opportunity for pregnancy were compared with 1,258 control women as part of a prospective case-control study of recent-onset RA in women. RESULTS: A 12-month or longer interval to pregnancy was found in 42% of RA cases compared with 34% of controls (odds ratio = 1.44, 95% confidence interval 1.10, 1.91). This difference was not accounted for by an older age when attempting to become pregnant among the RA cases compared with the controls. The result was unrelated to rheumatoid factor or HLA-DR4 status. CONCLUSION: Women with RA were found to have decreased fecundity prior to disease onset, compared with control women.

Adolescent↗

PubMed1991

A monoclonal antibody blocking the Schistosoma mansoni 28-kDa glutathione S-transferase activity reduces female worm fecundity and egg viability.

The protective effects of two different monoclonal antibodies (mAb) raised against the Schistosoma mansoni 28-kDa glutathione S-transferase (Sm 28 GST) were investigated. Two mAb of the same isotype (IgM) have been selected according to the blocking effect on Sm 28 GST enzymatic activity (S13) or the lack of blockade (H12). When passively transferred into Fischer rats, both S13 and H12 significantly reduced the worm burden. In BALB/c mice clear effects on female worm fecundity and egg viability were observed when the S13 mAb was transferred; these effects included significantly reduced loads of intestinal eggs, reduced egg hatching rates and an increased proportion of non-living eggs. No effect on egg production and egg hatching was observed in H12-treated mice. In addition, worm pairs recovered from S13-but not H12-treated mice laid significantly fewer eggs in vitro, and normal worm pairs incubated in vitro with the S13 mAb produced significantly fewer eggs than those incubated with H12 mAb. The impairment of egg hatching ability was also reproduced in vitro by the S13 mAb. These data suggest the existence of two different effector mechanisms induced by immunization with Sm 28 GST. The effect on the schistosome worm burden appears to be independent of GST activity whereas the effect on S. mansoni female fecundity and egg viability seems to be significantly linked to the inactivation of the enzymatic site.

Animals↗

PubMed1994

Schistosoma mansoni: relationship between low fecundity and reduced susceptibility to parasite infection in the snail Biomphalaria glabrata.

Biomphalaria glabrata snails which were not susceptible as juveniles to infection by Schistosoma mansoni were selectively bred (by self-fertilization) from the highly susceptible NMRI laboratory snail stock. The susceptibility rate among juvenile snails derived from interbreeding NMRI parents was initially 85-95%, but after several generations of selection, less than 5% of exposed snails became infected by the parasite. Selection for low susceptibility also resulted in a large proportion of snails that displayed low fecundity and produced abnormal egg masses. Individual adult snails which were isolated from an interbreeding population of nonselected NMRI snails usually produced well-developed egg masses each containing 15-30 embryos. However, when juvenile snails from this same population were reared in isolation and not allowed to cross-fertilize, many displayed a pattern of low fecundity and abnormal egg production similar to that observed in the selected low susceptible line. Furthermore, it was found that many of the isolated snails which exhibited low egg production were also not susceptible to parasitic infection.

Animals↗

PubMed1995

Biology of Ixodes (Pholeoixodes) hexagonus under laboratory conditions. Part II. Effect of mating on feeding and fecundity of females.

The effect of mating on the feeding and fecundity of Ixodes (Pholeoixodes) hexagonus females was studied under controlled laboratory conditions of 22-23 degrees C and 98% relative humidity. The feeding period of mated females was 6-15 days and 11-13 days for unmated females. The mean weight of the engorged mated females was 114.84 +/- 45.89 mg, whereas, that of the engorged unmated females was significantly lower (80.61 +/- 28.84 mg). During the initial slow feeding period, the weight of mated females increased 6.6 times. At the end of the blood feeding, they had increased their initial weight 35.5 times. Unmated females never entered the rapid engorgement phase and up to 12 days of feeding period their mean weight did not increase more than 9.2 times. The pre-oviposition periods of mated and unmated females were 6-15 days and 4-12 days, respectively. The mean of the egg production efficiency was 40.26 +/- 12.47% for mated females and 35.68 +/- 12.2% for unmated females. The mean of the mass conversion efficiency was 73.6 +/- 13.7% for mated females and 66.48 +/- 16.55% for unmated females. Sixty per cent of the eggs deposited by mated females hatched whereas only 1% of the eggs deposited by unmated females hatched. These results indicate that I. hexagonus females possess some predisposition for parthenogenesis and only fertility and not fecundity depends on mating.

Animals↗

PubMed1989

The effect of heterologous gonadotropins on the fecundity of rhesus monkeys.

Ovarian stimulation with heterologous gonadotropins over a period of a single month did not depress the fecundity or fecundability of 50 rhesus monkeys as compared to 60 untreated monkeys in a timed breeding colony. The birth rates, seasonality of births, interbirth intervals, and waiting time to the next pregnancy were not significantly different before treatment, after treatment, or among the untreated. The stillbirth rate was not increased after treatment.

Animals↗

PubMed2002

Fecundity of infertile women with minimal or mild endometriosis. A clinical study.

Despite significant developments in medical and surgical approaches for treating endometriosis, the optimal therapy has yet to be established. The relationship between prevalence of fecundity and stage of endometriosis according to their management was studied. Of 151 consecutive women with laparoscopy-proved endometriosis stage-1 and 2, operative laparoscopy was performed in 49, medical treatment in 59 and expectant management in 43 cases. During a 24-month period the cumulative pregnancy rates were found to be 36.7%, 30.5% and 20.9% respectively. Survival analysis showed that the probability of carrying the pregnancy beyond 20 weeks were 30.6%, 25.4% and 16.2% respectively. Diagnosis and treatment of early endometriosis is beneficial for the infertile women. Laparoscopic surgery seems to be the milestone of treatment in these cases, increasing the fecundity and involving minimal risk.

Adult↗

PubMed1996

Growth and fecundity of Oesophagostomum dentatum in high-level infections and after transplantation into naive pigs.

This experiment was designed to examine the growth, proportion of stages, and fecundity of an Oesophagostomum dentatum population by transplantation of a known small number of worms from a high-density population into helminth-naive recipient pigs. Approximately 1,500 4-week-old worms [69% fourth-stage larvae (L4), 31% adult worms] were transplanted into each of 5 recipient pigs (group B), and these pigs, along with a group of 5 high-level-infection control pigs (group C), were killed at 4 weeks after transplantation to determine and compare the worm burdens. By 2 weeks after transplantation and throughout the experiment, fecal egg counts of group B exceeded those of group C and the fecundity of the worms was higher, though not statistically significantly so, in the transplanted worms. In the recipient pigs, all worms (approx. 70% establishment) had developed to the adult stage and were significantly longer than worms recovered from the group C pigs.

Animals↗