Environmental and psychosocial risk factors for subfertility
Wesselink, Amelia Kent
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Fecundity, defined as the biologic capacity for reproduction, is measured operationally as time-to-pregnancy (TTP) among non-contracepting couples. While most couples conceive naturally within six menstrual cycles of trying, 10-24% of couples take longer than six cycles. Fecundity impairments are associated with long-term adverse health consequences including insulin resistance and gynecologic cancers, can cause substantial psychological and economic hardship, and cost over $5 billion annually in the U.S. Therefore, identifying risk factors for subfecundity in order to increase the chances of natural conception among pregnancy planners is an important public health goal. Environmental and psychosocial risk factors are understudied in relation to reproductive health. The goal of this dissertation is to examine the independent associations between exposure to tetrachloroethylene, perceived stress, and cigarette smoking and fecundability, the per cycle probability of conception. In study one, we used data from a retrospective cohort study of Cape Cod women who were exposed to tetrachloroethylene-contaminated drinking water in the 1960s-1980s to examine the relation between tetrachloroethylene exposure and fertility. We found that women with the highest modeled tetrachloroethylene exposure around the time of the pregnancy attempt had increased risk of TTP>12 months compared with unexposed women. Cumulative exposure, however, was not associated with elevated risk of TTP>12 months. Studies two and three used data from Pregnancy Study Online (PRESTO), a preconception cohort study of pregnancy planners from North America. In study two, we found that perceived stress levels in women, but not their male partners, were associated with lower fecundability, with little evidence of mediation by measured behavioral factors. In study three, we found that male current active smoking was associated with lower fecundability. In women, current smoking was only associated with reduced fecundability among women who smoked with high intensity and/or long duration. Passive smoking was not substantially associated with fecundability in either partner, but women exposed in utero to high intensity smoking had lower fecundability than unexposed women. Overall, we observed weak associations between tetrachloroethylene exposure, perceived stress, and active smoking and fertility among pregnancy planners. These findings indicate that environmental and psychosocial factors may play a role in the etiology of infertility. In addition, given that these exposures are common and modifiable, they may be important targets for public health interventions.