ABSTRACT
About 15% of American couples experience infertility (time-to-pregnancy >12 months) and more than 20% of
couples experience spontaneous abortion (SAB, pregnancy loss <20 weeks' gestation). The prevalence of
impaired fecundity has increased over the last decade and studies indicate that sperm counts have been
declining over the last four decades. Male factor contributes to 50% of infertility, yet epidemiologic research on
predictors of male infertility is scarce and male participation in reproductive health studies has been low. Even
less research has explored paternal influences of perinatal and pediatric health outcomes. With funding from the
NICHD, we launched Pregnancy Study Online (PRESTO) in June 2013 to assess the feasibility of conducting a
web-based preconception cohort study in North America to evaluate dietary, lifestyle, and medical determinants
of fecundity. Since June 2013, we have recruited more than 13,000 females and 3,000 of their male partners
from the United States and Canada. In this cohort, we have shown that male exposures, such as male sleep and
sugar-sweetened beverage intake, are strong determinants of fertility. In our NICHD-supported feasibility grant
(R21-HD094322), we demonstrated that at-home semen testing is feasible, with 400 men providing at least one
semen sample during a 3-year period. Preconception enrollment of men from the general population presents a
unique opportunity to examine how male factors influence semen quality, and the extent to which semen quality
and selected male factors predict reproductive and perinatal outcomes. We now propose to recruit an additional
2,000 men—including 800 in the semen testing substudy—to assess a broader set of aims: 1) to evaluate the
association of selected behavioral factors with poor semen quality, focusing on common but understudied factors
for which studies are limited or inconclusive (e.g. poor or inadequate sleep, bicycling, marijuana use, e-cigarette
use/vaping, and intake of sugar-sweetened, caffeinated, and alcoholic beverages); 2) to assess the extent to
which poor semen quality predicts subfertility, SAB, and adverse perinatal outcomes (shorter gestational length
and lower infant birthweight); and 3) to evaluate male factors in relation to risk of SAB and adverse perinatal
outcomes, and the extent to which these associations are mediated by semen quality. Importantly, we will assess
exposures jointly with female factors to better investigate causal pathways. Increased granularity of sleep and
activity exposures will be collected through a pilot aim to examine the feasibility of disseminating FitBit actigraphs
to a subset of 100 participants. We have already shown that appreciable numbers of men are willing to enroll in
our preconception cohort study, that men are willing to perform at-home semen testing, and that the semen data
are within the range expected for the general population. The use of an innovative and cost-effective semen
testing method, the prospective study design, the established infrastructure of PRESTO, and the comprehensive
collection of risk factor data in both male and female partners are added strengths. Results from the proposed
study will have important public health and clinical implications for male reproductive health.