The intestines form early in pregnancy as a long straight tube. Before the tenth week of pregnancy, they develop into the separate organs making up the digestive system. Occasionally, the intestines are not completely connected or blocked (atresia). Sometimes there is a partial blockage (web) inside the intestine.
Any part of the intestines can be affected by atresia or stenosis. Duodenal atresia is one type. This occurs in around one in 6,000 births where the duodenum is closed off rather than being a tube. If the jejunum or ileum are affected, this is called ‘small bowel atresia’.
Small bowel atresia is more common than duodenal atresia. We do not know how exactly how many babies are born with small bowel atresia each year but we do know that it affects boys and girls equally. It is more common in twins or multiple births and babies born prematurely or with low birthweight.
Colonic atresia, affecting the large bowel, is very rare.
Small bowel atresia affects two areas of the small bowel – the jejunum and the ileum. The jejunum is the section of small bowel after the duodenum and is where the majority of nutrients are absorbed. The ileum is the main part of the small bowel, making up over half of its entire length, and connects to the large bowel. The blockage can affect any part of the ileum or jejunum.