Persistent organochlorine pollutants and menstrual cycle characteristics

An evolving body of evidence suggests an adverse relation between persistent organochlorine pollutants (POPs) and menstruation, though prospective longitudinal measurement of menses is limited and served as the impetus for study. We prospectively assessed the relation between a mixture of persistent organochlorine compounds and menstrual cycle length and duration of bleeding in a cohort of women attempting to become pregnant. Eighty-three (83%) women contributing 447 cycles for analysis provided a blood specimen for the quantification of 76 polychlorinated biphenyls and seven organochlorine pesticides, and completed daily diaries on menstruation until a human chorionic gonadotropin confirmed pregnancy or 12 menstrual cycles without conception. Gas chromatography with electron capture detection was used to quantify concentrations (ng g(-1)serum); enzymatic methods were used to quantify serum lipids (mg dL(-1)). A linear regression model with a mixture distribution was used to identify chemicals grouped by purported biologic activity that significantly affected menstrual cycle length and duration of bleeding adjusting for age at menarche and enrollment, body mass index, and cigarette smoking. A significant 3-d increase in cycle length was observed for women in the highest tertile of estrogenic PCB congeners relative to the lowest tertile (β=3.20; 95% CI 0.36, 6.04). A significant reduction in bleeding (<1 d) was observed among women in the highest versus lowest tertile of aromatic fungicide exposure (γ=-0.15; 95% CI -0.29, -0.00). Select POPs were associated with changes in menstruation underscoring the importance of assessing chemical mixtures for female fecundity.

Clustering of fecundability within women

Adverse pregnancy outcomes have long been observed to cluster within women resulting in the inclusion of past reproductive history in clinical assessments and perinatal scoring systems. However, limited study has focused on the clustering of fecundability as measured by time to pregnancy (TTP), despite growing evidence suggestive of a possible association with adverse pregnancy outcomes known to cluster within women. We sought to empirically evaluate the clustering of conception delay, and TTP more globally, in one of the few existing prospective pregnancy cohort studies that captured women's successive pregnancies. The study cohort comprised 544 women who contributed 1119 pregnancies in the U.S. Collaborative Perinatal Project. We used a discrete Cox frailty model to estimate the degree and significance of within-woman clustering of TTP. Women with an initial conception delay (TTP > 6 months) were older, less educated and had higher body mass indices than women not experiencing delays (TTP ≤ 6 months). Our analysis indicates that there is significant within-woman clustering of TTP (variance of the frailty = 0.80, [95% confidence interval 0.49, 1.11]) after adjusting for baseline maternal age, body mass index and education level. Similar to many other reproductive and perinatal outcomes, our findings suggest that TTP clusters within women. Identifying exposures or behaviours that affect TTP may offer strategies for reducing conception delay in future pregnancy attempts.

Validity of retrospectively reported behaviors during the periconception window

OBJECTIVE

To assess the validity of retrospectively reported maternal behaviors while attempting pregnancy.

STUDY DESIGN

Participants in a prospective pregnancy cohort study with periconception enrollment were queried about use of cigarettes, alcohol, vitamins and caffeine and the consumption of sport fish while attempting pregnancy. Prospective longitudinal data reported in daily diaries (gold standard) were compared with data obtained a decade later using a self-administered questionnaire. Agreement was assessed by percent agreement and Kappa coefficients.

RESULTS

Among the 82 participating women, percent agreement ranged from 54-74% for the 5 behaviors. Validity was highest for smoking (Kappa = 0.43, 95% confidence interval [CI]: 0.22, 0.65) followed by fish consumption (Kappa = 0.32, 95% CI: 0.09, 0.55), caffeine (Kappa = 0.21, 95% CI: 0.09, 0.51) and alcohol (Kappa = 0.20, 95% CI: 0.08, 0.33). There were no systematic differences in agreement by time to pregnancy or pregnancy outcome. Associations between smoking and alcohol consumption and pregnancy outcomes were highly sensitive to the levels of misclassification observed in this study.

CONCLUSION

Validity was poor to moderate for the 5 behaviors, though higher for more regular behaviors such as smoking and caffeine consumption. The potential for misreporting of periconception behaviors can affect inferences, and thus efforts to capture information prospectively should be promoted.

Organochlorine pesticides and endometriosis

Limited study of persistent organochlorine pesticides (OCPs) and endometriosis has been conducted. One hundred women aged 18-40 years who were undergoing laparoscopy provided 20 cm(3) of blood for toxicologic analysis and surgeons completed operative reports regarding the presence of endometriosis. Gas chromatography with electron capture was used to quantify (ng/g serum) six OCPs. Logistic regression was utilized to estimate the adjusted odds ratios (aOR) and 95% confidence intervals (CI) for individual pesticides and groups based on chemical structure adjusting for current cigarette smoking and lipids. The highest tertile of aromatic fungicide was associated with a fivefold risk of endometriosis (aOR=5.3; 95% CI, 1.2-23.6) compared to the lowest tertile. Similar results were found for t-nonachlor and HCB. These are the first such findings in a laproscopic cohort that suggest an association between OCP exposure and endometriosis. More prospective studies are necessary to ensure temporal ordering and confirm these findings.

Communicating serum chemical concentrations to study participants: follow up survey

BACKGROUND

A considerable literature now supports the importance of effective communication with study participants, including how best to develop communication plans focusing on the uncertainty of health risks associated with particular environmental exposures. Strategies for communicating individual concentrations of environmental chemicals in human biological samples in the absence of clearly established safe or hazardous levels have been discussed from a conceptual basis and to a lesser extent from an empirical basis. We designed and evaluated an empirically based communication strategy for women of reproductive age who previously participated in a prospective study focusing on persistent environmental chemicals and reproductive outcomes.

METHODS

A cohort of women followed from preconception through pregnancy or up to 12 menstrual cycles without pregnancy was given their individual serum concentrations for lead, dichloro-2,2-bisp-chlorophenyl ethylene, and select polychlorinated biphenyl congeners. Two versions of standardized letters were prepared depending upon women's exposure status, which was characterized as low or high. Letters included an introduction, individual concentrations, population reference values and guidance for minimizing future exposures. Participants were actively monitored for any questions or concerns following receipt of letters.

RESULTS

Ninety-eight women were sent letters informing them of their individual concentrations to select study chemicals. None of the 89 (91%) participating women irrespective of exposure status contacted the research team with questions or concerns about communicated exposures despite an invitation to do so.

CONCLUSIONS

Our findings suggest that study participants can be informed about their individual serum concentrations without generating unnecessary concern.

Characteristics of prospectively measured vaginal bleeding among women trying to conceive

MikolajczykPrevious research has described variability in menstrual cycle lengths within and across women, though less attention has focused on characterising patterns of bleeding. While clinical definitions for menstrual bleeding are often given in standard textbooks, the validity of conventional definitions has not been empirically evaluated in epidemiological studies. The definition of menstrual bleeding may affect the analysis of time to pregnancy and pregnancy dating that relies upon the last menstrual period. We used daily records of vaginal bleeding from a prospective cohort study that included 74 women trying to become pregnant who reported 430 bleeding episodes. A longitudinal mixture model (PROC TRAJ) was used to classify patterns of bleeding. Among the first 74 bleeding episodes, 15% comprised only days with spotting or light bleeding (possibly representing non-menstrual bleeding given the length of the cycle defined by these bleeding episodes). When all 430 bleeding episodes were analysed, four distinct bleeding patterns emerged: (1) episodic bleeding comprising 1-3 days of spotting (10%), (2) bleeding lasting 3-6 days (40%), (3) bleeding lasting 6-8 days (33%), and (4) bleeding lasting 8-12 days (17%). These findings suggest that non-menstrual bleeding may be relatively common. Considerable variation in menstrual bleeding patterns is evident, and as such is likely to impact fecundity-related endpoints or gestational age estimates that rely upon menstrual cycle dates. The association between bleeding patterns and female fecundity awaits future research.

Analysis of the expression of putatively imprinted genes in bovine peri-implantation embryos

The application of assisted reproductive technologies (ART) has been shown to induce changes in the methylation of the embryonic genome, leading to aberrant gene expression, including that of imprinted genes. Aberrant methylation and gene expression has been linked to the large offspring syndrome (LOS) in bovine embryos resulting in increased embryonic morbidity and mortality. In the bovine, limited numbers of imprinted genes have been studied and studies have primarily been restricted to pre-implantation stages. This study reports original data on the expression pattern of 8 putatively imprinted genes (Ata3, Dlk1, Gnas, Grb10, Magel2, Mest-1, Ndn and Sgce) in bovine peri-implantation embryos. Two embryonic developmental stages were examined, Day 14 and Day 21. The gene expression pattern of single embryos was recorded for in vivo, in vitro produced (IVP) and parthenogenetic embryos. The IVP embryos allow us to estimate the effect of in vitro procedures and the analysis of parthenogenetic embryos provides provisional information on maternal genomic imprinting. Among the 8 genes investigated, only Mest-1 showed differential expression in Day 21 parthenogenetic embryos compared to in vivo and IVP counterparts, indicating maternal imprinting of this gene. In addition, our expression analysis of single embryos revealed a more heterogeneous gene expression in IVP than in in vivo developed embryos, adding further to the hypothesis of transcriptional dysregulation induced by in vitro procedures, either by in vitro maturation, fertilization or culture. In conclusion, effects of genomic imprinting and of in vitro procedures for embryo production may influence the success of bovine embryo implantation.

Disentangling causal paths between obesity and in vitro fertilization outcomes: an intractable problem?

Research questions should be appropriate for the available data. Disentangling causal paths between obesity and in vitro fertilization outcomes may be an intractable problem, but other research questions of clinical importance can be addressed through appropriate study designs and analytic methods.

Household pesticides and the risk of Wilms tumor

BACKGROUND

Previous epidemiologic studies have suggested that exposure to pesticides in utero and during early childhood may increase the risk for development of childhood cancer, including Wilms tumor, a childhood kidney tumor.

OBJECTIVES

In this analysis we evaluated the role of residential pesticide exposure in relation to the risk of Wilms tumor in children using data from a North American case-control study.

METHODS

The National Wilms Tumor Study Group (NWTSG) collected information on exposure to residential pesticides from the month before pregnancy through the diagnosis reference date using detailed phone interviews from 523 case mothers and 517 controls frequency matched on child's age and geographic region and identified by list-assisted random digit dialing. Pesticides were grouped according to type of pesticide and where they were used.

RESULTS

A slightly increased risk of Wilms tumor was found among children of mothers who reported insecticide use [odds ratio (OR) = 1.4, 95% confidence interval (CI), 1.0-1.8; adjusted for education, income, and the matching variables]. Results from all other categories of pesticides were generally close to the null.

CONCLUSIONS

This study is the largest case-control study of Wilms tumor to date. We were unable to confirm earlier reports of an increased risk for Wilms tumor among those exposed to residential pesticides during pregnancy through early childhood.

Time to pregnancy and multiple births

BACKGROUND

Mothers of multiples are alleged to be more fecund than mothers of singletons. Some authors have suggested monitoring twinning rates for assessing temporal changes in a population's reproductive health.

METHODS

Using a nested case-control design, we estimated the odds of a multiple birth in relation to fecundity in the US Collaborative Perinatal Project inclusive of 8546 pregnant women who reported a known time-to-pregnancy (TTP) upon enrolment in the cohort, 1959-1966. Case mothers comprised 81 women giving birth to twins/triplets; control mothers comprised 243 women giving birth to singletons matched to case mothers on maternal age at a ratio of 3:1. The odds ratio (OR) for a multiple birth within 6 months of trying adjusting for maternal age and prior pregnancies was estimated using logistic regression. Discrete time Cox regression analysis was also utilized to estimate the fecundability OR.

RESULTS

Women with a TTP of <or=6 months were more likely to have a multiple birth than women reporting a TTP of >6 months [OR=1.95; 95% confidence interval (95% CI)=1.09-3.51]. Excluding pregnancies after 13+ months resulted in a loss of precision (OR=2.14; 95% CI=0.90-5.04).

CONCLUSIONS

These data support higher fecundity among mothers of multiples than mothers of singletons.

Environmental influences on female fecundity and fertility

An increasing body of evidence suggests that environmental exposures are adversely influencing female fecundity and fertility. Endocrine-disrupting compounds (EDCs) are of particular concern, due to their ability to interfere with the body's hormonal milieu. An overview of the literature regarding the effect of EDCs on female fecundity and fertility end points such as puberty, menstruation, endometriosis, time to pregnancy, pregnancy loss, reproductive senescence, and secondary sex ratio is presented. Methodologic challenges in studying the effects EDCs on sensitive reproductive end points are discussed and include exposure to mixtures, the choice of biologic media in which to measure compounds, laboratory methods, and varying modeling techniques. Also reviewed are novel technologies for home-based biospecimen collection and testing that offer promise for field-based research aimed at addressing questions about environmental influences on female fecundity and fertility.

Is conception delay a risk factor for reduced gestation or birthweight?

Previous studies have suggested an association between delays in conception and adverse perinatal outcomes, specifically, low birthweight and preterm birth. We investigated the relationship between conception delay (defined as >6 months to become pregnant) and three perinatal outcomes: low birthweight (LBW; <2500 g), preterm birth (PTB; <37 weeks), and small-for-gestational-age (SGA; <10th percentile weight for given gestational age) using data from the Collaborative Perinatal Project. The study cohort was limited to pregnancies with a known time-to-pregnancy (n = 8465; 15%). Generalised estimating equations were used to estimate odds ratios (OR) and 95% confidence intervals [CI] for risk of adverse perinatal outcomes accounting for the clustering of pregnancy outcomes for women with more than one pregnancy. After adjusting for confounders, all ORs were close to the null (LBW, OR = 1.01; 95% CI = 0.86, 1.20), (PTB, OR = 1.10; 95% CI = 0.95, 1.27), (SGA, OR = 1.06; 95% CI = 0.91, 1.25). Thus, we found no evidence to support an adverse relationship between conception delay and decrements in gestation or birthweight among this select sample of fertile women, even after varying the cut-point for defining conception delay.

Birth of a cloned calf derived from a vitrified hand-made cloned embryo

The hand-made cloning (HMC) technique describes a simplified nuclear transfer process without the need for micromanipulators. The technique involves manual bisection of zona-free oocytes, selection of cytoplasts by Hoechst staining and fusion of a single somatic cell and two cytoplasts. In this proof-of-principle experiment, the objective was to examine the developmental competence of HMC embryos following embryo transfer. Modifications to the original method include not selecting of matured oocytes and simultaneous fusion of cytoplasts and karyoplast. Blastocyst rates for embryos cultured in the glass oviduct system as singles (10.5%; 24/228) or in pairs (16.1%; 36/224) did not differ significantly. Fresh and vitrified–thawed blastocysts were transferred to 16 synchronised recipients (three to four embryos per recipient). Ultrasound examination on Days 35–45 showed an initial pregnancy rate of 43.8% (7/16) and a pregnancy rate >8 months of 12.5% (2/16). A male cloned calf (42 kg) derived from a vitrified HMC blastocyst was delivered by Caesarean section on Day 271. The birth and ongoing survival (15 months, 243 kg) of a healthy and apparently normal calf, combining both HMC and vitrification technologies, provides a ‘proof of principle’ of the technology and a promising alternative to traditional nuclear-transfer techniques.

Characterisation and phylogenetic analysis of the VP7 proteins of serotype G6 and G8 human rotaviruses

Serotype G6 and G8 rotaviruses are rarely found in man and may have originated in animals. Human serotype G6 and G8 rotaviruses, isolated from hospitalised children at various locations in Australia, were characterised. Deduced amino acid sequences of the major neutralising antigen, V7, showed significant identity to the cognate proteins of prototype human and bovine G6 and G8 viruses, respectively, and the strains reacted with G6 and G8 serotype-specific neutralising monoclonal antibodies, respectively, in an enzyme immunoassay. The VP4 type was determined as P[14] for all strains tested. Phylogenetic analysis of these and other human and bovine VP7 sequences suggested that a single inter-species transmission event, possibly from cattle, may have led to the emergence of G6 viruses in man. In contrast, the exchange of genes between human and bovine G8 viruses may have occurred onmore than one occasion, or these genes may have originated in a different host.

Presenilin 2 expression in neuronal cells: induction during differentiation of embryonic carcinoma cells

Mutations in the presenilin 1 and 2 (PS1 and PS2) genes cause most cases of early onset Alzheimer's disease. The genes encode two homologous multipass membrane proteins. Since the endogenous expression of PS2 has been poorly analyzed to date, we studied PS2 expression and localization in cultured human neuroblastoma cells and mouse neuronal cells. PS2 was mainly detected as a full-length protein of about 52 kDa in these cells and in brain, in contrast to PS1 that is mainly detected as endoproteolytic N-terminal and C-terminal fragments. Using immunofluorescence we found that like PS1, PS2 colocalized with markers of the endoplasmic reticulum-Golgi intermediate compartment, ERGIC-53 and beta-COP. Double labeling for PS1 and PS2 indicated that both proteins are colocalized in neuroblastoma SH-SY5Y cells. To study PS2 expression during differentiation, mouse embryonic carcinoma P19 cells were treated with retinoic acid. We found minimal PS2 expression in undifferentiated cells, an increase from day 2, and a maximum at day 8 after treatment. PS1 expression remained constant during this period. The differential expression of PS1 and PS2 within the P19 cells following retinoic acid treatment indicates different utilization or temporal requirements for these proteins during neuronal differentiation.