AbstractsMedical & Health Science

Spontaneous abortion (SAB) is the unexpected loss of a conceptus early in pregnancy. Methodologic limitations such as left truncation bias, recall bias, and misclassification have prevented investigators from identifying risk factors related to this adverse pregnancy outcome. The objective of this dissertation was to examine the associations of body size, caffeine consumption, and history of oral contraceptive (OC) use with SAB risk among a prospective cohort of pregnancy planners in Denmark. In study 1, we examined SAB risk in relation to body size as measured by body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), height, and location of typical weight gain. We found that overall obesity (defined as BMI230) was associated with an increased risk of SAB, especially for pregnancy losses before 8 gestational weeks. Increasing WHR and increasing height were associated with a decreased risk ofSAB. Underweight, WC, and location of weight gain were not materially associated with SAB risk. The second study evaluated risk of SAB in relation to consumption of caffeine and caffeinated beverages before conception and during early pregnancy. We found that women who consumed higher amounts of coffee per day before pregnancy had a slightly higher risk of SAB. Overall, increased caffeine consumption during early pregnancy was also associated with higher risk of SAB. Study 3 assessed the risk of SAB in relation to self-reported history of OC use, evaluated in terms of recency, duration, and formulation of the most recent pill. Recent and longer durations of OC use were independently associated with a decreased risk of SAB. When stratified by maternal age, younger women ( < 30 years) had an increased risk of SAB with longer duration but older women (~30 years) had a decreased risk of SAB.