The prevalence of unplanned pregnancy and associated factors in Britain: findings from the third National Survey of Sexual Attitudes and Lifestyles (Natsal-3)

BACKGROUND: Unplanned pregnancy is a key public health indicator. We describe the prevalence of unplanned pregnancy, and associated factors, in a general population sample in Britain (England, Scotland, and Wales). METHOD: We did a probability sample survey, the third National Survey of Sexual Attitudes and Lifestyles (Natsal-3), of 15 162 men and women aged 16–74 years in Britain, including 5686 women of child-bearing age (16–44 years) who were included in the pregnancy analysis, between Sept 6, 2010, and Aug 31, 2012. We describe the planning status of pregnancies with known outcomes in the past year, and report the annual population prevalence of unplanned pregnancy, using a validated, multicriteria, multi-outcome measure (the London Measure of Unplanned Pregnancy). We set the findings in the context of secular trends in reproductive health-related events, and patterns across the life course. FINDINGS: 9·7% of women aged 16–44 years had pregnancies with known outcome in the year before interview, of which 16·2% (95% CI 13·1–19·9) scored as unplanned, 29·0% (25·2–33·2) as ambivalent, and 54·8% (50·3–59·2) as planned, giving an annual prevalence estimate for unplanned pregnancy of 1·5% (1·2–1·9). Pregnancies in women aged 16–19 years were most commonly unplanned (45·2% [30·8–60·5]). However, most unplanned pregnancies were in women aged 20–34 years (62·4% [50·2–73·2]). Factors strongly associated with unplanned pregnancy were first sexual intercourse before 16 years of age (age-adjusted odds ratio 2·85 [95% CI 1·77–4·57], current smoking (2·47 [1·46–4·18]), recent use of drugs other than cannabis (3·41 [1·64–7·11]), and lower educational attainment. Unplanned pregnancy was also associated with lack of sexual competence at first sexual intercourse (1·90 [1·14–3·08]), reporting higher frequency of sex (2·11 [1·25–3·57] for five or more times in the past 4 weeks), receiving sex education mainly from a non-school-based source (1·84 [1·12–3·00]), and current depression (1·96 [1·10–3·47]). INTERPRETATION: The increasing intervals between first sexual intercourse, cohabitation, and childbearing means that, on average, women in Britain spend about 30 years of their life needing to avert an unplanned pregnancy. Our data offer scope for primary prevention aimed at reducing the rate of unplanned conceptions, and secondary prevention aimed at modification of health behaviours and health disorders in unplanned pregnancy that might be harmful for mother and child. FUNDING: Grants from the UK Medical Research Council and the Wellcome Trust, with support from the Economic and Social Research Council and the Department of Health.