Recruitment, retention and characteristics of women in a prospective study of preconceptional risks to reproductive outcomes: experience of the Diana Project.

Preterm delivery, low birthweight, and intrauterine growth retardation are common and recalcitrant problems in many countries. Although much remains to be learned, we know particularly little about the relationships between preconceptional and early pregnancy exposures and these and other reproductive outcomes. The study presented here was primarily designed to investigate the relationships between nutritional exposures measured before and during pregnancy and reproductive outcomes. This paper describes methods used to recruit the required 1000 preconceptional women from the collaborating health maintenance organisation (HMO) and the retention of participants in this time-intensive study. The results presented demonstrate that an adequate completion rate (66.3%), and a remarkably representative sample of women that poses few threats to the study's validity, can be obtained by population-based recruitment of women from an HMO.