A baby's gastrointestinal tract is divided into 2 segments: the small intestine and the large intestine. The small intestine is made up of 3 parts: the duodenum (the segment connected to the stomach), the jejunum (where most the liquid in food is absorbed), and the ileum (which empties into the large intestine). The large intestine is also called the colon. There are many causes of bowel obstruction in the fetus. Most are caused by an atresia, a narrowing at some point in the small intestine. A bowel obstruction is named by the place in the small intestine where it occurs: duodenal atresia, jejunal atresia, ileal atresia, or colon atresia.
Your fetus’s bowel obstruction may have been discovered one of two ways. You may have undergone a routine ultrasound which showed a segment of bowel which was dilated, or larger than normal. This is a clue to your doctor that there is a problem with the intestine. This dilation happens because while in the uterus the fetus constantly swallows amniotic fluid. This narrowing can slow down or stop the flow of amniotic fluid in the intestine causing it to swell, so that is appears too large in an ultrasound.
The second way a bowel obstruction can be discovered is by the development of polyhydramnios, (the build up of too much amniotic fluid). Because of the blockage in the intestine, the normal flow of amniotic fluid is stopped. It accumulates on the outside of the baby- inside your uterus. Your uterus size may suddenly grow very large alerting your doctor to a possible problem. Your doctor may then order an ultrasound study. The ultrasound study can confirm a problem in the intestine.
For women whose fetuses have a bowel obstruction, it is important to have a thorough evaluation of the condition. This might include an ultrasound, a fetal echocardiogram (a special ultrasound to look at the baby's heart), and an amniocentesis. Some fetuses with bowel obstruction have abnormal chromosomes. An amniocentesis is recommended because it can determine not only the sex of the baby, but whether or not there is a problem with the chromosomes. Your amniotic fluid level and the growth of your baby will be watched carefully(link to becoming a new patient). Time intervals for ultrasound studies are decided on an individual basis. You may be at risk for a delivery before your due date because polyhydramnios (extra amniotic fluid) can lead to preterm labor. You and your obstetrician will determine your delivery plan.