Antioxidant Status, Diet and Early Pregnancy

Only one-fourth to one-third of fertilized human eggs are likely to survive to produce a term baby. The causes of these reproductive failures are substantially unknown, but scientific evidence suggests that they may, in part, be due to exposures such as pre-conception nutrition, that may result in insults to the oocyte and periconceptual embryo. Early reproductive events may have long-lasting impact as several have recently been identified as antecedents to adult-onset diseases. The goal of this prospective epidemiologic study is to evaluate the hypothesis that increased oxidative stress results in delayed time-to-pregnancy or early pregnancy loss. Recently, reactive oxygen species (ROS) have been associated with spontaneous abortion, preeclampsia, and premature preterm rupture of the membranes in women and defective sperm function in men. In living cells ROS are formed continuously as a consequence of both biochemical reactions and external factors. In this prospective cohort study of healthy couples who are planning pregnancy, we are evaluating time-to-pregnancy, defined as the number of menstrual cycles from the cessation of contraception to a clinically recognized pregnancy, and early unrecognized pregnancy loss. Unrecognized pregnancy and subsequent early loss will be determined by measuring urinary human chorionic gonadotropin (hCG). Diet will be assessed in both partners prior to conception using the Block food frequency questionnaire and serum assays for the antioxidants vitamins C and E, the carotenoids, and selenium. Two urinary biomarkers of oxidative stress, 8-hydroxy-2'-deoxyguanosine and F2a-isoprostanes, and a serum biomarker of antioxidative capacity, oxygen radical absorbance capacity, will be measured in the women. The proposed study has a number of strengths: 1) it is large and prospective in design, with diet and oxidative stress measured prior to conception; 2) a highly sensitive and specific assay for hCG will be used to detect conceptions as early as the time of implantation; 3) dietary intake and biomarker assays of antioxidant status will be assessed twice during the preconception period using state-of-the-art assessment methods including a diet calibration substudy; 4) the proposed research has the potential to fill gaps in our understanding of the role of diet in achieving successful conception, an area where very little investigation has been done.