Male alcohol consumption and fecundability.

STUDY QUESTION: Does male alcohol consumption affect fecundability? SUMMARY ANSWER: In data pooled across Danish and North American preconception cohort studies, we found little evidence of an association between male alcohol consumption and reduced fecundability. WHAT IS KNOWN ALREADY: Experimental and clinical studies have shown that alcohol affects male reproductive physiology, mainly by altering male reproductive hormones and spermatogenesis. However, few epidemiologic studies have examined the association between alcohol consumption and male fertility. STUDY DESIGN, SIZE, DURATION: Data were collected from two ongoing prospective preconception cohort studies: the Danish 'SnartForaeldre' (SF) study (662 couples) and the North American 'Pregnancy Study Online' (PRESTO) (2017 couples). Participants included in the current analysis were enrolled from August 2011 through June 2019 (SF) and from June 2013 through June 2019 (PRESTO). PARTICIPANTS/MATERIALS, SETTING, METHODS: Eligible men were aged ≥18 years in SF and ≥21 years in PRESTO, in a stable relationship with a female partner and not using contraception or receiving fertility treatment. In both cohorts, alcohol consumption/serving size was self-reported as number of beers (330 mL/12 oz.), glasses of white or red wine (120 mL/4 oz. each), dessert wine (50 mL/2 oz.) and spirits (20 mL/1.5 oz.). Overall alcohol consumption was categorized as none, 1-5, 6-13 and ≥14 standard servings per week. Total menstrual cycles at risk were calculated using data from female partners' follow-up questionnaires, which were completed every 8 weeks until self-reported pregnancy or 12 menstrual cycles, whichever came first. Analyses were restricted to couples that had been trying to conceive for ≤6 cycles at study entry. Proportional probability regression models were used to compute fecundability ratios (FRs) and 95% confidence interval (CIs). We adjusted for male and female age, female partner's alcohol consumption, intercourse frequency, previous history of fathering a child, race/ethnicity, education, BMI, smoking and consumption of sugar-sweetened beverages and caffeine. MAIN RESULTS AND THE ROLE OF CHANCE: The cumulative proportion of couples who conceived during 12 cycles of follow-up were 1727 (64.5%). The median (interquartile range) of total male alcohol consumption was 4.5 (2.0-7.8) and 4.1 (1.0-8.6) standard servings per week in the SF and PRESTO cohorts, respectively. In pooled analyses, adjusted FRs for male alcohol consumption of 1-5, 6-13 and ≥14 standard servings per week compared with no alcohol consumption were 1.02 (95% CI: 0.90-1.17), 1.10 (95% CI: 0.96-1.27) and 0.98 (95% CI: 0.81-1.18), respectively. For SF, adjusted FRs of 1-5, 6-13 and ≥14 standard servings per week compared with no alcohol consumption were 0.97 (95% CI: 0.73-1.28), 0.81 (95% CI: 0.60-1.10) and 0.82 (95% CI: 0.51-1.30), respectively. For PRESTO, adjusted FRs of 1-5, 6-13 and ≥14 standard servings per week compared with no alcohol consumption were 1.02 (95% CI: 0.88-1.18), 1.20 (95% CI: 1.03-1.40) and 1.03 (95% CI: 0.84-1.26), respectively. LIMITATIONS, REASONS FOR CAUTION: Male alcohol consumption was ascertained at baseline only, and we did not distinguish between regular and binge drinking. In addition, we had insufficient numbers to study the effects of specific types of alcoholic beverages. As always, residual confounding by unmeasured factors, such as dietary factors and mental health, cannot be ruled out. Comorbidities thought to play a role in the reproductive setting (i.e. cancer, metabolic syndrome) were not considered in this study; however, the prevalence of cancer and diabetes was low in this age group. Findings for the highest categories of alcohol consumption (6-13 and ≥14 servings/week) were not consistent across the two cohorts. WIDER IMPLICATIONS OF THE FINDINGS: Despite little evidence of an association between male alcohol consumption and reduced fecundability in the pooled analysis, data from the Danish cohort might indicate a weak association between reduced fecundability and consumption of six or more servings per week. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by the National Institutes of Health (R01-HD060680, R01-HD086742, R21-HD050264, R21-HD072326, R03-HD090315), the Novo Nordisk Foundation, Oticon Fonden, Politimester J.P.N. Colind og hustru Asmine Colinds mindelegat and Erna og Peter Houtveds studielegat. PRESTO receives in-kind donations from FertilityFriend.com, Kindara.com, Swiss Precision Diagnostics and Sandstone Diagnostics for the collection of data pertaining to fertility. Dr Wise serves as a consultant on uterine leiomyomata for AbbVie.com. All other authors declare no conflict of interest.

Birth weight for gestational age and the risk of infertility: a Danish cohort study.

STUDY QUESTION: Is birth weight for gestational age associated with infertility in adulthood among men and women? SUMMARY ANSWER: Being born small for gestational age (SGA) was associated with infertility in adulthood among men. WHAT IS KNOWN ALREADY: Fetal growth restriction may affect fertility, but results from previous studies have been inconsistent. STUDY DESIGN, SIZE, DURATION: In this population-based cohort study, we used data from a Danish birth cohort, including 5594 men and 5342 women born between 1984 and 1987. Information on infertility was obtained from Danish health registers during the period from the participants' 18th birthday and up until 31 December 2017. PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants were men and women born in two Danish municipalities, Aalborg and Odense. Information on birth weight and gestational age was obtained from birth records, and information on infertility diagnoses and fertility treatment was retrieved from the Danish National Patient Registry (NPR) and the Danish In Vitro Fertilisation (IVF) registry. Information on potential maternal confounders was obtained from questionnaires during pregnancy and was included in adjusted analyses. Logistic regression analysis was used to estimate crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for infertility according to birth weight for gestational age. MAIN RESULTS AND THE ROLE OF CHANCE: Men born SGA had a 55% higher risk of being diagnosed with or treated for infertility compared to men born appropriate for gestational age (AGA) (adjusted OR = 1.55, 95% CI: 1.09-2.21). The association attenuated after exclusion of men born with hypospadias or cryptorchidism (OR = 1.37, 95% CI: 0.93-2.01). No association was found between women's birth weight for gestational age and risk of infertility (adjusted OR = 1.00, 95% CI: 0.73-1.37). LIMITATIONS, REASONS FOR CAUTION: Estimation of gestational age is associated with some uncertainty and might have caused non-differential misclassification. The study design implicitly assumed similar distribution of reproductive and health-seeking behaviour across the groups that were compared. WIDER IMPLICATIONS OF THE FINDINGS: Men born SGA had a higher risk of infertility. Genital malformations may account for part of the observed association, but this must be explored further. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by Health, Aarhus University. No competing interests are declared. TRIAL REGISTRATION NUMBER: N/A.

Use of non-prescription analgesics and male reproductive function.

We studied the association between intake of non-prescription analgesics and semen quality and male reproductive hormone levels in a cross-sectional study among 1493 men. The men provided one semen (n=1493) and blood sample (n=1056) and filled in questionnaires on use of non-prescription analgesics (paracetamol, NSAIDs and combination drugs (yes/no)). Adjusting for age, study and other covariates, we observed no association between intake of non-prescription analgesics and markers of semen quality. Adjusting for age and time of day of blood sampling, users of non-prescription analgesics had a 10.4% (95% confidence interval (CI) 4.0-17.1%) higher testosterone level than non-users. When we stratified by medication type, the association between analgesics and higher testosterone was observed between users of non-steroidal anti-inflammatory drugs (NSAIDs) and combination drugs but not paracetamol. This study suggests that use of non-prescription analgesics is associated with slightly higher serum testosterone levels than non-use.

Environmental cadmium and lead exposure and anti-Müllerian hormone in pregnant women.

BACKGROUND: Anti-Müllerian Hormone (AMH) has been suggested as a marker for ovarian function. Cadmium and lead have been suggested to reduce female fecundity. In this study we aimed to investigate whether environmental exposure to cadmium and lead was associated with alterations in serum-AMH. MATERIALS AND METHOD: The associations between serum-AMH and whole blood cadmium or lead were investigated by general linear models in a population-based sample of 117 pregnant women. RESULTS: The mean concentrations of blood cadmium and lead were 0.71µg/L and 17.4µg/L, respectively. The mean serum-AMH was 17.3pmol/L. No association between lead and AMH was detected. In the cadmium analysis the adjusted mean AMH level (95% CI) in the highest exposure tertile was 12.4 (6.4;23.8) compared to 5.6 (2.7;11.4) in the lowest exposure tertile (p=0.06). CONCLUSION: The study provides suggestive evidence that environmental exposure to cadmium, but not lead, may alter the level of AMH.

No association between body mass index and sperm DNA integrity.

STUDY QUESTION: Is overweight associated with impaired sperm DNA integrity? SUMMARY ANSWER: High body mass index (BMI) is not associated with impaired sperm DNA integrity as assessed by the DNA Fragmentation Index (DFI). WHAT IS KNOWN ALREADY: Previous studies, based on fewer subjects and including mainly subfertile men, have shown conflicting results regarding the influence of overweight and obesity on sperm DNA integrity. STUDY DESIGN, SIZE, DURATION: This cross-sectional study was based on semen samples from 1503 men from the general population. PARTICIPANTS/MATERIALS, SETTING, METHODS: We included two cohorts (cohort A and B) of military recruits (n = 275, n = 304, respectively), one group (cohort C) of fertile men and men without known fertility problems (n = 724), and one group (cohort D) of men between 19 and 40 years without known fertility problems (n = 200). In all cohorts, data were available on BMI, DFI as measured by the sperm chromatin structure assay (SCSA), standard semen characteristics, and potential confounders (age, abstinence time, smoking habits). The subjects were categorized according to BMI into four groups: underweight (<18.5 kg/m(2)), normal weight (18.5-24.9 kg/m(2)), overweight (25.0-29.9 kg/m(2)) and obese (≥30.0 kg/m(2)). Using a linear regression model, the inter-group differences in DFI were calculated. Furthermore with the normal-weight group as the reference, the odds ratios (ORs) for DFI > 20% and DFI > 30%, were calculated for the other groups. Calculations were made for the material as a whole and after exclusion of cohort C which included proven fertile men. MAIN RESULTS AND THE ROLE OF CHANCE: We found that normal-weight men had significantly higher DFI than overweight men, with a mean difference of 1.13% (95% CI: 1.05-1.22%); P = 0.001). Overweight men had a reduced risk of having DFI ≥ 20% and DFI ≥ 30%, compared with normal-weight men; adjusted odds ratio (OR) = 0.61 (95% CI: 0.42-0.88; P < 0.01) and adjusted OR = 0.48 (95% CI: 0.28-0.84; P < 0.01), respectively. When excluding cohort C, the statistical significance was lost. Regarding standard semen parameters, we found that obese men had a higher percentage of progressive motile spermatozoa than normal-weight men; mean difference 1.15% (95% CI: 1.02-1.30%, P < 0.05) but the significance was lost when excluding cohort C. All other standard semen parameters were unaffected by BMI. LIMITATIONS, REASONS FOR CAUTION: A main limitation might be the cross-sectional nature of the data. Furthermore our study included a significant proportion of men with proven fertility (75% of cohort C, n = 550), and could therefore be biased toward fertility. WIDER IMPLICATIONS OF THE FINDINGS: Our study indicates that overweight per se is not associated with a higher level of sperm DNA damage. STUDY FUNDING/COMPETING INTERESTS: This research has been given grants from the following: EU 5th and 7th framework program (Inuendo and Clear projects, [Contracts no. QLK4-CT-2001-00202 and FP7-ENV-2008-1-226217)]), the Swedish Research Council (Grants No. 2007-2590, 521-2004-6072 and 521-2002-3907); the Swedish Governmental Funding for Clinical Research, Skåne county council's research and development foundation, MAS Funds, University Hospital MAS Foundation in Malmö, Crafoordska Fund, Ove Tulefjords Fund, Foundation for Urological Research, Fundacion Federico SA, and Gunnar Nilssons Cancer Fund. The authors declare that there are no conflicts of interest.

Prenatal exposure to environmental chemical contaminants and asthma and eczema in school-age children.

BACKGROUND: Emerging evidence suggests that prenatal or early-life exposures to environmental contaminants may contribute to an increased risk of asthma and allergies in children. We aimed to the explore associations of prenatal exposures to a large set of environmental chemical contaminants with asthma and eczema in school-age children. METHODS: We studied 1024 mother-child pairs from Greenland and Ukraine from the INUENDO birth cohort. Data were collected by means of an interview-based questionnaire when the children were 5-9 years of age. Questions from the ISAAC study were used to define asthma, eczema, and wheeze. We applied principal components analysis (PCA) to sixteen contaminants in maternal serum sampled during pregnancy, including perfluoroalkyl substances (PFASs), metabolites of diethylhexyl (DEHP) and diisononyl (DiNP) phthalates, PCB-153, and p,p'-DDE. Scores of five principal components (PCs) explaining 70% of the variance were included in multiple logistic regression models. RESULTS: In a meta-analysis that included both populations, the PC2 score, reflecting exposure to DiNP, was negatively associated with current eczema (OR 0.71, 95% CI 0.52-0.96). Other associations were not consistent between the two populations. In Ukrainian children, the PC3 score (DEHP) was positively associated with current wheeze (adjusted OR 1.56, 95% CI 1.03-2.37), whereas the PC5 score, dominated by perfluorooctanoic acid (PFOA), was inversely associated with current wheeze (OR 0.64, 0.41-0.99). In Greenlandic children, a negative association of PC4 (organochlorines) with ever eczema (OR 0.78, 0.61-0.99) was found. CONCLUSIONS: We found limited evidence to support a link between prenatal exposure to environmental chemical contaminants and childhood asthma and eczema.

Interactions between polymorphisms in the aryl hydrocarbon receptor signalling pathway and exposure to persistent organochlorine pollutants affect human semen quality.

Persistent organic pollutants (POPs) may affect male reproductive function. Many dioxin-like POPs exert their effects by activation of the aryl hydrocarbon receptor (AHR) signalling pathway. We analysed whether gene-environment interactions between polymorphisms in AHR (R554K) and AHR repressor (AHRR P185A) and serum levels of markers of POP exposure 1,1-bis-(4-chlorophenyl)-2,2-dichloroethene (p,p'-DDE) and 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) are associated with 21 parameters of male reproductive function in 581 proven-fertile European and Greenlandic men. In Greenlandic men, AHR variants significantly modified the association between serum levels of both p,p'-DDE and CB-153 and inhibin B levels, sperm chromatin integrity, and seminal zinc levels. In the total cohort, interactions between AHRR variants and serum levels of CB-153 were associated with sperm chromatin integrity and the expression of the pro-apoptotic marker protein Fas. The data indicate that susceptibility to adverse effects of POP exposure on male reproductive function is dependent on polymorphisms in genes involved in AHR signalling.

Age of menarche and time to pregnancy.

STUDY QUESTION: Is age of menarche (AOM) associated with subfecundity and/or infertility in adulthood? STUDY ANSWER: A late onset of menarche was associated with a slightly increased risk of subfecundity and infertility. WHAT IS KNOWN ALREADY: Abnormal age at onset of menarche is a risk factor for several diseases later in life, but the effect on infertility is unknown. STUDY DESIGN, SIZE AND DURATION: A cohort study of  73 107 pregnant Danish women enrolled in the Danish National Birth Cohort (DNBC) between 1996 and 2002 with self-reported data on AOM and waiting time to pregnancy (TTP). PARTICIPANTS/MATERIALS, SETTING AND METHODS: Information on AOM and TTP was collected through a computer-assisted telephone interview scheduled in pregnancy Week 12. We estimated adjusted odds ratios (ORs) with 95% confidence intervals (CIs) using multivariate logistic regression with TTP categorized as subfecundity (TTP ≥6 months) and infertility (TTP >12 months). Multiple imputation was performed to account for missing data. MAIN RESULTS AND THE ROLE OF CHANCE: We found trends towards higher odds of subfecundity and infertility with increasing age of menarche, using 13 years as the starting point. Among women reaching menarche at 15 years, the odds for subfecundity were 1.09 (95% CI: 1.03-1.15), and 1.17 (95% CI: 1.09-1.25) for women reaching menarche later than 15 years compared with the reference group of girls reaching menarche at 13 years. Additionally, women reaching menarche older than 15 years had an OR of infertility of 1.18 (95% CI: 1.08-1.29). Women younger than 11 years at menarche had lower odds of subfecundity. The results were generally attenuated when adjusting for women's age of pregnancy, but the significant positive trend of higher OR for subfecundity persisted, as did the higher OR for subfecundity among women experiencing menarche older than 15 years. LIMITATIONS, REASONS FOR CAUTION: We used retrospectively collected self-reported information on AOM and TTP. Information on male factors was limited in this cohort. We only included pregnant women and have therefore no data on women with untreated and unsuccessfully treated infertility, limiting the generalizability to women who became pregnant. WIDER IMPLICATION OF THE FINDINGS: This study indicates that the onset of menarche at 15 years or later is associated with subfecundity and infertility. STUDY FUNDING/COMPETING INTERESTS: The Danish National Research Foundation has established the Danish Epidemiology Science Centre that initiated and created the DNBC. The cohort is furthermore a result of a major grant from this Foundation. Additional support for the DNBC is obtained from the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Augustinus Foundation and the Health Foundation. This specific study was supported by a scholarship from the Ministry of Science and Innovation. No conflict of interest declared.

Indices of methylation in sperm DNA from fertile men differ between distinct geographical regions.

STUDY QUESTION: Which are the main determinants, if any, of sperm DNA methylation levels? SUMMARY ANSWER: Geographical region resulted associated with the sperm methylation status assessed on genome-wide repetitive sequences. WHAT IS KNOWN ALREADY: DNA methylation level, assessed on repetitive sequences from peripheral blood lymphocyte, can vary with age, gender, alcohol consumption and white blood cell counts. STUDY DESIGN, SIZE, DURATION: A cross-sectional study. Individual data were collected from 269 young healthy men of proven fertility living in three geographical regions: Inuits from Greenland, Caucasians from Warsaw (Poland) and Kharkiv (Ukraine). Semen samples were collected between May 2002 and February 2004 and aliquots were immediately frozen. PARTICIPANTS/MATERIALS, SETTING, METHODS: We estimated sperm DNA global methylation level (DGML) in two ways. First DNA methylation in repetitive DNA sequences (LINE-1, Satα and Alu) was quantified by PCR pyrosequencing after bisulfite conversion and second by flow cytometry (FCM) using fluorescently labeled monoclonal antibodies anti-5-methylcytosine. We analyzed whether personal characteristics and habits, body mass index, semen quality parameters, sperm chromatin integrity, biomarkers of accessory gland function and the plasma concentration of reproductive hormones were associated with sperm DNA methylation levels in men. Associations were evaluated by analysis of variance and linear regression analyses. MAIN RESULTS AND THE ROLE OF CHANCE: The geographical location emerged as the main determinant when using the methylation level in repetitive sequences. FCM DGML results were not associated with those from repetitive sequence analysis. No other consistent associations between methylation markers and the assessed variables were identified across countries. LIMITATIONS, REASONS FOR CAUTION: The methods used are only surrogates of the actual sperm methylome and the methylation levels at individual specific loci were not explored. WIDER IMPLICATIONS OF THE FINDINGS: Sperm DGML is relatively independent from semen quality parameters and is a new candidate biomarker for epidemiological studies of the impact of environmental contaminants on male fertility. STUDY FUNDING/COMPETING INTERESTS: The study is part of the project CLEAR (Climate change, Environmental contaminants and Reproductive health) supported by the European Commission 7th framework program, contract no: FP7-ENV-2008-1-226217. No competing interest is declared.

Body mass index in young school-age children in relation to organochlorine compounds in early life: a prospective study.

OBJECTIVE: To investigate the association between maternal pregnancy and estimated postnatal serum concentrations of the organochlorines 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) and body mass index (BMI) z-scores in 5- to 9-year-old children. METHODS: Maternal sera from the INUENDO birth cohort (2002-2004) comprising mother-child pairs (N=1109) from Greenland, Warsaw (Poland), and Kharkiv (Ukraine) were analysed for CB-153 and p,p'-DDE, using gas chromatography-mass-spectrometry, and were grouped into tertiles for statistical analyses. A toxicokinetic model was used to estimate the first 12 months cumulative exposure to the compounds. Associations between these compounds and child age- and sex-specific BMI z-scores were calculated at follow-up (2010-2012), using multiple linear regression analysis. RESULTS: No clear associations between pregnancy CB-153 and p,p'-DDE and child BMI were observed (the pooled differences in BMI z-score (95% confidence interval) comparing 3rd tertile to 1st tertile were -0.07 (-0.32 to 0.18) and -0.10 (-0.30 to 0.10) kg m(-2), respectively). For postnatal CB-153 and p,p'-DDE and BMI, the overall differences in BMI z-score comparing 3rd tertile to 1st tertile were 0.12 (-0.15 to 0.39) and -0.03 (-0.20 to 0.27) kg m(-2), respectively. CONCLUSIONS: This follow-up study of Greenlandic, Polish and Ukrainian populations showed no clear association between pregnancy and postnatal exposure to p,p'-DDE and CB-153 and BMI at the age of 5-9 years.

Menstrual cycle characteristics in fertile women from Greenland, Poland and Ukraine exposed to perfluorinated chemicals: a cross-sectional study.

STUDY QUESTION: Does perfluorooctane sulfonate (PFOS) and perfluorooctanate (PFOA) exposure disrupt the menstrual cyclicity? SUMMARY ANSWER: The female reproductive system may be sensitive to PFOA exposure, with longer menstrual cycle length at higher exposure. WHAT IS KNOWN ALREADY: PFOS and PFOA are persistent man-made chemicals. Experimental animal studies suggest they are reproductive toxicants but epidemiological findings are inconsistent. STUDY DESIGN, SIZE, DURATION: A cross-sectional study including 1623 pregnant women from the INUENDO cohort enrolled during antenatal care visits between June 2002 and May 2004 in Greenland, Poland and Ukraine. PARTICIPANTS/MATERIALS, SETTING, METHODS: Information on menstrual cycle characteristics was obtained by questionnaires together with a blood sample from each pregnant woman. Serum concentrations of PFOS and PFOA were measured by liquid chromatography tandem mass spectrometry. Multiple imputations were performed to account for missing data. The association between PFOS/PFOA and menstrual cycle length (short cycle: ≤24 days, long cycle: ≥32 days) and irregularities (≥7 days in difference between cycles) was analyzed using logistic regression with tertiles of exposure. Estimates are given as adjusted odds ratios (ORs) with 95% confidence intervals (CIs). MAIN RESULTS AND THE ROLE OF CHANCE: Higher exposure levels of PFOA were associated with longer menstrual cycles in pooled estimates of all three countries. Compared with women in the lowest exposure tertile, the adjusted OR of long cycles was 1.8 (95% CI: 1.0; 3.3) among women in the highest tertile of PFOA exposure. No significant associations were observed between PFOS exposure and menstrual cycle characteristics. However, we observed a tendency toward more irregular cycles with higher exposure to PFOS [OR 1.7 (95% CI: 0.8; 3.5)]. The overall response rate was 45.3% with considerable variation between countries (91.3% in Greenland, 69.1% in Poland and 26.3% in Ukraine). LIMITATIONS, REASONS FOR CAUTION: Possible limitations in our study include varying participation rates across countries; a selected study group overrepresenting the most fertile part of the population; retrospective information on menstrual cycle characteristics; the determination of cut-points for all three outcome variables; and lacking information on some determinants of menstrual cycle characteristics, such as stress, physical activity, chronic diseases and gynecological disorders, thus confounding cannot be excluded. WIDER IMPLICATIONS OF THE FINDINGS: The generalizability of the study results is restricted to fertile women who manage to conceive and women who do not use oral contraceptives when getting pregnant or within 2 months before getting pregnant. To our knowledge only one previous epidemiological study has addressed the possible association between perfluorinated chemical exposure and menstrual disturbances. Though pointing toward different disturbances in cyclicity, both studies suggest that exposure to PFOA may affect the female reproductive function. This study contributes to the limited knowledge on effects of exposure to PFOA and PFOS on female reproductive function and suggests that the female reproductive system may be affected by environmental exposure to PFOA. STUDY FUNDING/COMPETING INTEREST(S): Supported by a scholarship from Aarhus University Research Foundation. The collection of questionnaire data and blood samples was part of the INUENDO project supported by The European Commission (Contract no. QLK4-CT-2001-00 202), www.inuendo.dk. The Ukrainian part of the study was possible by a grant from INTAS (project 012 2205). Determination of PFOA and PFOS in serum was part of the CLEAR study (www.inuendo.dk/clear) supported by the European Commission's 7th Framework Program (FP7-ENV-2008-1-226217). No conflict of interest declared.

Moderate alcohol intake and menstrual cycle characteristics.

STUDY QUESTION: Does moderate alcohol intake affect menstrual cycle characteristics among women in the Danish population? SUMMARY ANSWER: Levels of alcohol exposure as seen in this study do not substantially affect the menstrual cycle. WHAT IS KNOWN ALREADY: Animal studies indicate alcohol-induced disruptions of the reproductive system, but previous epidemiological studies addressing the possible association between alcohol intake and the menstrual cycle are sparse. STUDY DESIGN, SIZE, DURATION: A cross-sectional study with retrospectively collected data including 82 146 pregnant Danish women in the Danish National Birth Cohort (DNBC) enrolled during the years 1996-2002. PARTICIPANTS/MATERIALS, SETTING, METHODS: Information on weekly alcohol consumption and menstrual cycle characteristics before pregnancy was obtained through a computer-assisted telephone interview in pregnancy Week 12-16. The associations between weekly alcohol consumption and menstrual cycle irregularity (≥7 days difference between cycles) and length (short cycle: ≤24 days, long cycle: ≥32 days) were analysed using logistic regression with weekly alcohol intake categorized into abstainers (0 drinks per week), low (0.5-2.0 drinks per week), moderate (2.5-14.0 drinks per week) and high (14.0-86.5 drinks per week). Estimates are given as adjusted odds ratios with 95% confidence intervals. MAIN RESULTS AND THE ROLE OF CHANCE: The overall participation rate was 60% of the women invited. We found that a high weekly alcohol consumption was not associated with menstrual cycle disturbances. We observed higher odds of irregular and short cycles among abstainers when compared with women with a low weekly alcohol consumption, but found no trend of more cycle disturbances with higher alcohol consumption. LIMITATIONS, REASONS FOR CAUTION: Possible limitations in our study include a risk of selection bias due to the moderate participation rate and the use of retrospective information on alcohol exposure and menstrual cycle characteristics before getting pregnant. The higher odds of irregular and short cycles among abstainers may reflect other health problems in these women rather than an actual effect of alcohol on the menstrual cycle. WIDER IMPLICATIONS OF THE FINDINGS: The generalizability of the study results is restricted to women who manage to conceive and women who do not use oral contraceptives within 2 months before getting pregnant. This study suggests that the menstrual cycle is not substantially affected by higher alcohol consumption among the participating women. STUDY FUNDING/COMPETING INTEREST(S): Supported by a scholarship from Aarhus University Research Foundation. The Danish National Research Foundation has established the Danish Epidemiology Science Centre that initiated and created the DNBC. The cohort is furthermore a result of a major grant from this Foundation. Additional support for the DNBC is obtained from the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Augustinus Foundation and the Health Foundation. No conflict of interest declared.

Long-term effects of prenatal exposure to perfluoroalkyl substances on female reproduction.

STUDY QUESTION: Does prenatal exposure to perfluoroalkyl substances (PFASs) have long-term effects on female reproductive function?. SUMMARY ANSWER: Our results suggest an association between in utero exposure to perfluorooctanoic acid (PFOA) and delay in age of menarche. WHAT IS KNOWN ALREADY: Previous cross-sectional studies have reported possible effects of PFASs on female reproduction including reduced fecundity, delayed puberty and accelerated age at menopause. Only limited data exist from follow-up studies on long-term implications of prenatal exposure to PFASs. STUDY DESIGN, SIZE, DURATION: In this study we used data from a Danish population-based cohort established in 1988-1989. Of 1212 eligible pregnant women, 965 participated. Follow-up was initiated in 2008 on the female offspring at ∼20 years of age. Three hundred and sixty seven (84%) daughters answered a questionnaire and 267 (61%) daughters furthermore attended clinical examinations which were conducted in 2008-2009. PARTICIPANTS/MATERIALS, SETTING, METHODS: The final study population consisted of 343 daughters of which 254 had attended the clinical examinations and 89 had answered the questionnaire only. Levels of PFASs in maternal serum from pregnancy week 30 were used as a measure of prenatal exposure and related to age of menarche, menstrual cycle length, levels of reproductive hormones and follicle number of the daughters. Data were divided into three groups according to tertiles of maternal concentrations of PFASs (low, medium, high). MAIN RESULTS AND THE ROLE OF CHANCE: In adjusted regression analyses, daughters exposed to higher levels of PFOA in utero had a 5.3 (95% confidence interval: 1.3; 9.3) months later age of menarche compared with the reference group of lower PFOA. Crude (P = 0.05) and adjusted (P = 0.01) trend tests also indicated a relationship between higher prenatal PFOA exposure and delay of menarche. LIMITATIONS, REASONS FOR CAUTION: We did not measure the exact amount of PFASs to which the daughters had been exposed prenatally. Instead we used PFAS concentrations in maternal serum as surrogates. However, PFASs are efficiently transferred to the fetus via placenta. Information on age of menarche was collected retrospectively but the time interval for recall in our study was relatively short (2-10 years). The remaining outcome measures depended on participation in clinical examination which reduced the number of observations leading to limited statistical power and risk of selection bias. WIDER IMPLICATIONS OF THE FINDINGS: Since PFASs can be detected in humans all over the world, effects of prenatal exposure on female reproductive function later in life may have wide health implications. STUDY FUNDING/COMPETING INTEREST(S): The study was supported by the Danish Council for Independent Research (271-05-0296, 09-065631), the Danish Ministry of Interior and Health (0-302-02-18/5), the Danish Council for Strategic Research (09-067124 (Centre for Fetal Programming), 09-063072, 2101-06-0005), the Novo Nordisk Foundation, the Aarhus University Research Foundation, the Frimodt-Heineke Foundation, the Foundation of Maria Dorthea and Holger From, the Beckett-Foundation, the Research Grant of Organon and the Foundation of Lily Benthine Lund. There are no competing interests. TRIAL REGISTRATION NUMBER: Not applicable.

Non-linear association between androgen receptor CAG and GGN repeat lengths and reproductive parameters in fertile European and Inuit men.

Recently the dogma that there is an inverse linear association between androgen receptor (AR) CAG and GGN polymorphisms and receptor activity has been challenged. We analysed the pattern of association between 21 male reproductive phenotypes and AR CAG/GGN repeat lengths in 557 proven-fertile men. A linear association was only found between sperm DNA fragmentation index (DFI) and CAG length, and between inhibin B and GGN length. Men with longer CAG then the reference (22-24), had higher oestradiol levels, whereas men with shorter CAG stretches had a higher DFI and a higher proportion of Fas-positive germ cells. Subjects with either short or long CAG had increased seminal levels of prostate-specific antigen and neutral α-glucosidase activity. Compared to men with the median GGN length of 23, those with shorter GGN repeats had higher levels of inhibin B, higher proportions of normal and progressive sperm, and a higher fraction of Fas-positive sperm, while men with longer GGN had higher oestradiol levels. These data indicate that at least for some markers of male reproductive function the association with CAG or GGN repeat length is curvilinear.

Maternal smoking during pregnancy and reproductive health of daughters: a follow-up study spanning two decades.

STUDY QUESTION: Does in utero exposure to constituents of cigarette smoke have a programming effect on daughters' age of menarche and markers of long-term reproductive health? SUMMARY ANSWER: In utero exposure to constituents of cigarette smoke was associated with earlier age of menarche and--to a lesser extent--changes in the testosterone profile of the young women. WHAT IS KNOWN ALREADY: Studies observe potential effects of in utero exposure to constituents of cigarette smoke on the intrauterine formation of female gonads, but the consequences on long-term reproductive health in daughters remain unclear. STUDY DESIGN, SIZE AND DURATION: A prospective cohort study was designed using data from 965 pregnant women enrolled prior to a routine 30th-week antenatal examination at a midwifery practice in Denmark from 1988 to 1989 and a follow-up of their 19-21-year-old daughters in 2008. PARTICIPANTS/MATERIALS, SETTING AND METHODS: The pregnant women provided information on lifestyle factors during pregnancy, including the exact number of cigarettes smoked per day during the first and the second trimesters. A total of 438 eligible daughters were asked to complete a web-based questionnaire on reproductive health and subsequently invited to participate in a clinical examination during 2008. Of the 367 daughters (84%) who answered the questionnaire, 267 (61%) agreed to further examination. Information on menstrual pattern was provided at examination, blood samples were drawn to be analyzed for serum levels of reproductive hormones [FSH, LH, estradiol (E(2)), sex hormone-binding globulin, anti-Müllerian hormone, dehydroepiandrosterone-sulphate (DHEAS), free testosterone and free E(2)] and number of follicles (2-9 mm) were examined by transvaginal ultrasound. The daughters were divided into three exposure groups according to the level of maternal smoking during first trimester [non-exposed (reference), low-exposed (mother smoking >0-9 cigarettes/day) and high-exposed (mother smoking ≥ 10 cigarettes/day)]. Data were analyzed by multiple regression analyses in which we adjusted for potential confounders. Both crude and adjusted test for trend were carried out using maternal smoking during the first trimester as a continuous variable. MAIN RESULTS AND THE ROLE OF CHANCE: We observed an inverse association between in utero exposure to constituents of cigarette smoke and age of menarche (P = 0.001). Daughters exposed to >0-9 cigarettes/day debuted with -2.7 [95% confidence interval (CI) -5.2 to -0.1] percentage earlier age of menarche, whereas daughters exposed to ≥ 10 cigarettes/day had -4.1 (95% CI: -6.6 to -1.5) percentage earlier age of menarche corresponding to 6.5 (95% CI: -10.7 to -2.2) months. There was a non-significant tendency towards lower levels of testosterone and DHEAS with increasing in utero exposure to constituents of cigarette smoke but no associations with follicle number, cycle length or serum levels of the other reproductive hormones were observed. LIMITATIONS AND REASONS FOR CAUTION: We collected information on age of menarche retrospectively but the recall time was relatively short (2-10 years) and the reported values were within the normal range of Caucasians. Analyses of reproductive hormones are presented only for the group of daughters who were non-users of hormonal contraceptives because users were excluded, leaving only a low number of daughters available for the analyses (n = 75), as reflected in the wide CIs. The analyses of hormones were further adjusted for menstrual phase at time of clinical examination (follicular, ovulation and luteal phase) because blood samples were not collected on a specific day of the menstrual cycle. WIDER IMPLICATIONS OF THE FINDINGS: This study supports the limited evidence of an inverse association between maternal smoking during pregnancy and age of menarche and further addresses to what extent reproductive capacity and hormones may be programmed by maternal smoking during pregnancy. A trend toward earlier maturation of females is suggested to have implications on long-term reproductive function. STUDY FUNDING/COMPETING INTEREST(S): Supported by a scholarship from The Lundbeck Foundation (R93-A8476). No conflict of interest declared.

Male-mediated infertility in sons of building painters and gardeners: a nationwide register-based follow-up study.

AIM: To investigate whether sons of gardeners and building painters have increased risk of infertility in comparison with sons of bricklayers, carpenters and electricians. METHODS: Participants were men born 1965-1984 in Denmark whose fathers the year before birth had worked as gardeners, painters, bricklayers, carpenters or electricians (N=22,978). Cases of infertility were identified by Danish registers, and participants were followed-up for up to 24 years after their 20th birthday. RESULTS: Sons of gardeners did not have increased risk of infertility. Hazard ratios for sons of painters fluctuated around the null in main analyses but were 1.6 (98% CI: 1.0-2.5) and 1.7 (95% CI: 0.9-3.2) in the subset of participants with smallest risk of paternal exposure misclassification. CONCLUSIONS: Working as gardener or building painter was not related to increased risk of infertility among the next generation of males in main analyses. However, inherent limitations in data may have attenuated true associations.

Exposure to perfluorinated compounds and human semen quality in Arctic and European populations.

BACKGROUND: Perfluorinated compounds (PFCs) have been suspected to adversely affect human reproductive health. The aim of this study was to investigate the associations between PFC exposure and male semen quality. METHODS: PFCs were measured in serum from 588 partners of pregnant women from Greenland, Poland and Ukraine who provided a semen sample, using liquid chromatography tandem mass spectrometry. Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS) and perfluorononanoic acid (PFNA) could be detected in >97% of the samples. The associations between levels of these compounds and semen volume, sperm concentration, total sperm count, motility and morphology were assessed. RESULTS: Across countries, sperm concentration, total sperm count and semen volume were not consistently associated with PFOS, PFOA, PFHxS or PFNA levels. The proportion of morphologically normal cells was 35% lower [95% confidence interval (CI): 4-66%) for the third tertile of PFOS exposure as compared with the first. A similar reduction was found in relation to increasing PFHxS levels. At the third PFOA exposure tertile, the percentage of motile spermatozoa was 19% (95% CI: 1 to 39%) higher than in the first. CONCLUSIONS: The most robust finding in the present study was the negative associations between PFOS exposure and sperm morphology suggesting adverse effects of PFOS on semen quality, possibly due to interference with the endocrine activity or sperm membrane function. It cannot be excluded that this association and the positive association between PFOA and semen motility, which was not consistent across countries, might represent a chance finding due to the multiple statistical tests being performed.