The prevalence of couple infertility in the United States from a male perspective: evidence from a nationally representative sample.

Infertility is a couple-based fecundity impairment, although population level research is largely based upon information reported by female partners. Of the few studies focusing on male partners, most focus on the utilization of infertility services rather than efforts to estimate the prevalence and determinants of infertility as reported by male partners. Data from a nationally representative sample of men aged 15-44 years who participated in the 2002 National Survey of Family Growth (NSFG) were used to estimate the prevalence of infertility and determinants of longer time-to-pregnancy (TTP) using the novel current duration (CD) approach. Using backward recurrence time parametric survival methods, we estimated infertility prevalence (TTP > 12 months) and time ratios (TR) associated with TTP as derived from males' reported CD of their pregnancy attempt. The estimated prevalence of infertility was 12.0% (95% CI: 7.0, 23.2). Longer TTP was associated with older male age (35-45 vs. 17-24 years) (TR: 2.49; 95% CI: 1.03, 6.03), biological childlessness (TR: 1.53; 95% CI: 1.07, 2.19) and lack of health insurance (TR: 1.73; 95% CI: 1.02, 2.94) after controlling for the differences in couples' age and other socioeconomic factors. The prevalence of infertility based on male reporting is consistent with estimates of infertility in the US found in prospective cohort studies and CD studies based on female reporting. Our findings suggest that male partners can reliably inform about couple infertility. Interventions and services aimed at reducing couple infertility should include attention to male factors associated with longer TTP identified in this study.

Cumulative incidence rate of medical consultation for fecundity problems--analysis of a prevalent cohort using competing risks.

STUDY QUESTION: What is the incidence of medical consultation for fecundity problems in the French population, taking into account pregnancy occurrence and resumption of contraceptive use?. SUMMARY ANSWER: Considering the occurrence of a pregnancy and resumption of use of contraception as competing risks, the cumulative incidence rate of medical consultation for fecundity problems was 9.0% [95% confidence interval (CI): 6.5%; 11.9%] after 12 months of unprotected intercourse and 12.2% [95% CI: 9.6%; 15.3%] after 24 months. WHAT IS KNOWN ALREADY: Estimates of the prevalence of medical consultation due to involuntary infertility among couples who have sought a pregnancy for more than 12 months range from 25 to 50%. Most of the studies however are limited by retrospective data collection, without considering the duration of time since the beginning of the period of unprotected intercourse (PUI) and without considering medical consultation for fecundity problems as a competing risk. STUDY DESIGN, SIZE, DURATION: This study is based on the Observatory of Fecundity in France survey, a population-based probability survey designed to estimate the frequency of involuntary infertility on a nationwide basis and to explore the associations with environmental factors. Women answered two telephone questionnaires, the first at the time of enrolment in 2007, the second at follow-up 1 year later. The current analysis was performed among a subsample of 6577 women recruited before or during a PUI and followed-up for 1 year. PARTICIPANTS/MATERIALS, SETTING, METHODS: The study sample comprised 940 women aged 18-44 years who had a PUI between the time of enrolment and the 1-year follow-up, and who had not consulted a physician for fecundity problems for the current PUI prior to enrolment. Women reported all the medical consultations they had because of difficulties becoming pregnant during the current PUI. The date of each consultation was carefully assessed. In France, women can consult a gynaecologist directly without referral by their general practitioner. The occurrence of a pregnancy and resumption of contraceptive use were considered as informative censoring events, using a competing risk model. MAIN RESULTS AND THE ROLE OF CHANCE: Using the competing risk survival model, the cumulative incidence rate of first consultation was 9.0% [95% CI: 6.5%; 11.9%] 12 months after the start of the PUI and 12.2% [95% CI: 9.6%; 15.3%] after 24 months. The Kaplan-Meier method, which does not take competing risks into account, yielded substantially higher estimates: 26.0% [95% CI: 18.8%; 32.5%] at 12 months and 56.8% [95% CI: 44.2%; 66.6%] at 24 months. Among the 219 women who had attempted to become pregnant for at least 12 months, cumulative incidences of first medical consultations were 28.2% [18.7-38.9%] 24 months after the start of the PUI, and 31.2% [21.3- 42.4%] after 36 months. The rates were higher among nulliparous but non-nulligravid women, followed by nulligravid women, as compared with parous women. Age was not strongly related to the occurrence of medical consultation. LIMITATIONS, REASONS FOR CAUTION: The main limitation of this study is the number of women lost to follow-up (29.7%). In addition, results regarding the absence of an age effect should be taken with caution as few women in our study were aged over 35 years. Although such an attrition rate is commonly observed in prospective studies in the general population, it could have induced a selection bias that may have led to an underestimation of the rates of medical consultation. Sensitivity analyses, using the inverse probability weighting method suggest that our results are unlikely to be biased. WIDER IMPLICATIONS OF THE FINDINGS: This study reveals frequencies of medical consultation for fertility problems, which, after considering competing events such as pregnancy in a relevant statistical model, are lower than generally reported in the literature. The results also indicate the existence of a difference between the potential need and the actual use of medical care for fecundity problems. This suggests a need for studies to look for factors other than medical recommendations that may play a role in the patterns of medical seeking behaviours for fecundity problems, such as women's reproductive history, socio-economic characteristics or accessibility to infertility services. STUDY FUNDING/COMPETING INTEREST(S): The study was funded by grants from ANR (French Agency for Research, SEST call on Environmental and Occupational Health), ANSES (French Agency for Food, environmental and Occupational Health Safety, EST call on Environmental and Occupational Health), InVS (French Institute for Public Health Surveillance). The team of Environmental Epidemiology applied to Fecundity and Reproduction has been funded by an AVENIR grant from Inserm (2007). Authors declare no conflict of interest.

Quality control of computational fluid dynamics in indoor environments.

Computational fluid dynamics (CFD) is used routinely to predict air movement and distributions of temperature and concentrations in indoor environments. Modelling and numerical errors are inherent in such studies and must be considered when the results are presented. Here, we discuss modelling aspects of turbulence and boundary conditions, as well as aspects related to numerical errors, with emphasis on choice of differencing scheme and computational grid. Illustrative examples are given to stress the main points related to numerical errors. Finally, recommendations are given for improving the quality of CFD calculations, as well as guidelines for the minimum information that should accompany all CFD-related publications to enable a scientific judgment of the quality of the study.

Gas-phase ion-molecule chemistry of borate and boronate esters.

Borate esters B(OR)3 and boronate esters RB(OR)2 undergo ion-molecule reactions to yield both addition products (by an implied radiative emission mechanism), ligand exchange, and proton transfer products, in both positive and negative ion modes. Although an acidity for CH3B(OR)2 could not be determined, HOB(OR)2 has an acidity between acetaldehyde and nitromethane. In light of the negligible polar electron acceptor properties of the -B(OR)2 group, that functionality must therefore be one of the best resonance electron acceptor groups known, almost half again as effective as the nitro group.