Bayesian probability

Sociology

Regional science

Bayesian hierarchical modeling

Unintended consequences

Unintended pregnancy

Population

Biology

Demography

Political science

Econometrics

Artificial intelligence

Bayesian inference

Economics

Geography

MEDLINE

Family planning

Pregnancy

Computer science

Research methodology

Genetics

Medicine

Environmental health

The Lancet Global Health

Estimates of pregnancy incidence by intention status and outcome indicate how effectively women and couples are able to fulfil their childbearing aspirations, and can be used to monitor the impact of family-planning programmes. We estimate global, regional, and subregional pregnancy rates by intention status and outcome for 1990-2014.We developed a Bayesian hierarchical time series model whereby the unintended pregnancy rate is a function of the distribution of women across subgroups defined by marital status and contraceptive need and use, and of the risk of unintended pregnancy in each subgroup. Data included numbers of births and of women estimated by the UN Population Division, recently published abortion incidence estimates, and findings from surveys of women on the percentage of births or pregnancies that were unintended. Some 298 datapoints on the intention status of births or pregnancies were obtained for 105 countries.Worldwide, an estimated 44% (90% uncertainty interval [UI] 42-48) of pregnancies were unintended in 2010-14. The unintended pregnancy rate declined by 30% (90% UI 21-39) in developed regions, from 64 (59-81) per 1000 women aged 15-44 years in 1990-94 to 45 (42-56) in 2010-14. In developing regions, the unintended pregnancy rate fell 16% (90% UI 5-24), from 77 (74-88) per 1000 women aged 15-44 years to 65 (62-76). Whereas the decline in the unintended pregnancy rate in developed regions coincided with a declining abortion rate, the decline in developing regions coincided with a declining unintended birth rate. In 2010-14, 59% (90% UI 54-65) of unintended pregnancies ended in abortion in developed regions, as did 55% (52-60) of unintended pregnancies in developing regions.The unintended pregnancy rate remains substantially higher in developing regions than in developed regions. Sexual and reproductive health services are needed to help women avoid unintended pregnancies, and to ensure healthy outcomes for those who do experience such pregnancies.Dutch Ministry of Foreign Affairs and UK Aid from the UK Government.

Global, regional, and subregional trends in unintended pregnancy and its outcomes from 1990 to 2014: estimates from a Bayesian hierarchical model