OBJECTIVES: to present issues associated with recruitment of women in maternity hospitals to a population-based case-control study of very preterm birth. DESIGN: a descriptive study of the recruitment process. SETTING: all maternity hospitals, including three providing neonatal intensive care services, in Victoria, Australia from April 2002 to April 2004. PARTICIPANTS: cases were women who had a singleton birth between 20 and 31+6 weeks of gestation. Controls were a random selection of women having a singleton birth of at least 37 completed weeks of gestation in the same time period as the cases. MEASUREMENTS AND FINDINGS: ethical approval was obtained from 73 of 77 maternity hospitals. Hospitals considered that privacy laws required that women should be approached initially by hospital staff for recruitment into the research study. Extensive effort was put into liaising with hospital personnel, determining hospital-specific protocols for approaching women and developing relationships with doctors, midwives and ward clerks. Recurrent reminders were provided to all hospitals. Of the 2785 women (cases and controls) ascertained as eligible, 13% of cases with surviving babies, 11% of controls and 74% of cases whose babies did not survive were not approached to participate in the study. Within these groups, there was variation by gestation and hospital. Once women were approached, 72% were interviewed. The interview response proportion was 50%. KEY CONCLUSIONS: recruitment to studies in the maternity setting in the postpartum period is a challenge. Barriers to recruitment that may have introduced selection bias in this study include: recruitment at many hospitals; short postnatal hospital stay; reliance on hospital staff to make the first approach to women; and low response from women whose babies did not survive. A dialogue between researchers and clinical midwives is proposed to explore ways of increasing researchers' understanding of the complex and demanding hospital environment, and to improve research awareness among clinical midwives.