New oral contraception study: pilot trial report. Royal College of General Practitioners' Manchester Research Unit

As a preliminary to a new large cohort study of steroidal contraception, two pilot studies have been carried out. The first estimated that the prevalence of never-use of oral contraceptives among sexually active women aged 16 to 29 years was only 5.1% which means it will be impractical to recruit never-user controls for the main study. The prevalence of cigarette smoking in ever-users of oral contraceptives was 37% in contrast to never-users of whom only 20% smoked.The second pilot study tested the acceptability of a new recruitment procedure. Two hundred and seventy doctors recruited 1574 women - 98% of these women understood and accepted the need to record their National Health Service number. The mean age of this patient cohort was 22.5 years, 65% were single and 37% were cigarette smokers. One-tenth of women had had coitus before the age of 16 years, but only 4% had started using oral contraceptives before that age.