Background We launched the Boston University Pregnancy Study Online (PRESTO) to assess the feasibility of carrying out an internet-based preconception cohort study in the U.S. and Canada. Methods We recruited female participants age 21–45 and their male partners through internet advertisements, word of mouth, and flyers. Female participants were randomized with 50% probability to receive a subscription to FertilityFriend.com (FF), a web-based program that collects real-time data on menstrual characteristics. We compared recruitment methods within PRESTO, assessed the cost-efficiency of PRESTO relative to its Danish counterpart (Snart-Gravid), and validated retrospectively-reported date of last menstrual period (LMP) against FF data. Results After 99 weeks of recruitment (2013–2015), 2,421 women enrolled; 1,384 (57%) invited their male partners to participate, of whom 693 (50%) enrolled. Baseline characteristics were balanced across randomization groups. Cohort retention was similar among those randomized vs. not randomized to FF (84% vs. 81%). At study enrollment, 56%, 22%, and 22% couples had been trying to conceive for <3, 3–5, and ≥6 months, respectively. The cost per subject enrolled was $146 (2013 $US), which was similar to our companion Danish study and half that of a traditional cohort study. Among FF users who conceived, >97% reported their LMP on the PRESTO questionnaire within 1 day of the LMP recorded via FF. Conclusions Use of the internet as a method of recruitment and follow-up in a North American preconception cohort study was feasible and cost-effective.

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Selection bias is a potential concern in all epidemiologic studies, but it is usually difficult to assess. Recently, concerns have been raised that internet-based prospective cohort studies may be particularly prone to selection bias. Although use of the internet is efficient and facilitates recruitment of subjects that are otherwise difficult to enroll, any compromise in internal validity would be of great concern. Few studies have evaluated selection bias in internet-based prospective cohort studies. Using data from the Danish Medical Birth Registry from 2008 to 2012, we compared six well-known perinatal associations (e.g., smoking and birth weight) in an inter-net-based preconception cohort (Snart Gravid n = 4,801) with the total population of singleton live births in the registry (n = 239,791). We used log-binomial models to estimate risk ratios (RRs) and 95% confidence intervals (CIs) for each association. We found that most results in both populations were very similar. For example, maternal obesity was associated with an increased risk of delivering a macrosomic infant in Snart Gravid (RR = 1.5; 95% CI: 1.2, 1.7) and the total population (RR = 1.5; 95% CI: 1.45, 1.53), and maternal smoking of >10 cigarettes per day was associated with a higher risk of low birth weight (RR = 2.7; 95% CI: 1.2, 5.9 vs. RR = 2.9; 95% CI: 2.6, 3.1) in Snart Gravid and the total population, respectively. We cannot be certain that our results would apply to other associations or different populations. Nevertheless, our results suggest that recruitment of reproductive aged women via the internet may be no more prone to selection bias than traditional methods of recruitment.

ObjectiveWe examined the association between lifestyle factors and menstrual cycle characteristics among nulliparous Danish women aged 18–40 years who were participating in an Internet-based prospective cohort study of pregnancy planners.MethodsWe used cross-sectional data collected at baseline to assess the association of age, body mass index (BMI), physical activity, alcohol and caffeine consumption, and smoking with the prevalence of irregular cycles, short (≤25 days) and long (≥33 days) cycles, and duration and amount of menstrual flow. We used log-binomial and multinomial logistic regression to estimate prevalence ratios and 95% confidence intervals.ResultsLow physical activity and heavy alcohol consumption were associated with an increased prevalence of irregular periods. High BMI, smoking, and caffeine and alcohol consumption were related to an increased prevalence of short menstrual cycles and heavy menstrual bleeding. Women in their mid-to-late thirties had shorter and lighter menstrual flow, but a lower prevalence of irregular cycles, compared with women 18–25 years of age.DiscussionIn this study, increased age, high BMI, and sedentary behavior were associated with menstrual-pattern irregularities. These factors may influence the balance and level of endogenous hormones conducive to optimal menstrual function.