Intervention Now to Eliminate Repeat Unintended Pregnancy in Teenagers (INTERUPT): a systematic review of intervention effectiveness and cost-effectiveness, and qualitative and realist synthesis of implementation factors and user engagement.

The UK has one of the highest rates of teenage pregnancies in Western Europe. One-fifth of these are repeat pregnancies. Unintended conceptions can cause substantial emotional, psychological and educational harm to teenagers, often with enduring implications for life chances. Babies of teenage mothers have increased mortality and are at a significantly increased risk of poverty, educational underachievement and unemployment later in life, with associated costs to society. It is important to identify effective, cost-effective and acceptable interventions.