Abstract
STUDY QUESTION: What are the relations among birthweight (BW), semen parameters and birth outcomes in a population-based sample? SUMMARY ANSWER: BW is unrelated to semen parameters, which are in turn unrelated to birth outcomes. WHAT IS KNOWN ALREADY: In clinical settings, there has been suggestion that semen parameters are related to BW when comparing fertile and infertile men; however, findings have been less clear in more general populations. STUDY DESIGN, SIZE, DURATION: Questionnaire data and semen samples were collected at baseline from 427 male participants of the population-based Longitudinal Investigation of Fertility and the Environment (LIFE) prospective cohort study from 2005 to 2009, who were followed prospectively to assess pregnancy outcomes among 226 singleton births. PARTICIPANTS/MATERIALS, SETTING, METHODS: Men of at least 18 years of age who were married or in a committed relationship and trying to conceive were eligible for participation; physician-diagnosed infertility was an exclusion criterion. Participants were recruited from two geographic areas and semen samples were analyzed for 34 quality parameters categorized as general, motility, morphology, sperm head and sperm chromatin structure using methods including computer-aided semen analysis integrated visual optical system and sperm chromatin structure assay. Linear and mixed models were used for statistical analysis of the relations between men's BW, semen parameters, and BW, gestational age at delivery, birth length, head circumference and ponderal index of singleton births. MAIN RESULTS AND THE ROLE OF CHANCE: No association was observed between male BW and semen parameters or birth outcomes. Few associations were observed between semen parameters and birth outcomes, and the observed statistically significant associations were isolated and without a consistent pattern that would suggest an association between BW and birth outcomes. LIMITATIONS, REASONS FOR CAUTION: Men's BW was self-reported and may be subject to some imprecision. Semen analysis was performed the day after collection, an approach that impacts the assessment of motility and that may limit inference from our analyses of motility measures. In addition, inclusion criteria for selection into the cohort limits generalizability to generally healthy couples trying to conceive and without known subfertility. WIDER IMPLICATIONS OF THE FINDINGS: Despite suggestions from prior studies of male in utero exposures impacting BW and male reproductive health, there appears to be little support for such relations in this generally healthy population. STUDY FUNDING/COMPETING INTEREST(S): Supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (N01-HD-3-3355, N01-HD-3-3356 and NOH-HD-3-3358). The authors report no competing interests, and a Memo of Understanding with the National Institute of Occupational Safety and Health (NIOSH) for semen analysis. TRIAL REGISTRATION NUMBER: Not applicable.