evidence: People who have high risk pregnancies may have underlying conditions that increase their risk, or they may have developed conditions during pregnancy that put them at high risk of complications. [...] High risk pregnancies aren’t very common, but they’re not rare either. There’s not much research on the subject, but the World Health Organization notes that they affect about 15% of pregnancies. [...] A high-risk pregnancy can affect people of any age, especially in those with existing health conditions. But there are more likely to be risks during the teenage years and in those aged over 35.