About 1 in 2,500 babies born in the UK has cystic fibrosis (CF). This inherited condition can affect the digestion and lungs. Babies with CF may not gain weight well, and have frequent chest infections. Screening means that babies with CF can be treated early with a high energy diet, medicines and physiotherapy. Although a child with CF may still become very ill, early treatment is thought to help them live longer, healthier lives. If babies are not screened for CF and they do have the condition, they can be tested later but parents may have an anxious time before CF is recognised.