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What Is Polyhydramnios?


Polyhydramnios is a condition where there is excess fluid surrounding the baby in the womb. There is often no cause found but sometimes this can be associated with problems related to the baby’s swallowing.


What Is Polyhydramnios?

The fluid that surrounds the baby inside the womb is called amniotic fluid. The amniotic fluid is produced by the baby producing urine (wee). The amniotic fluid is also swallowed by the baby. The amount of amniotic fluid surrounding the baby is therefore due to the balance between how much urine the baby is producing and how much the baby is able to swallow. In cases of polyhydramnios there is more fluid than expected surrounding the baby. This may have been detected by you measuring large for dates and referred for a growth scan or found by chance during an antenatal ultrasound scan. The amount of extra fluid is measured during an ultrasound scan and is categorised as mild, moderate or severe. In the majority of mild cases there is no cause for the polyhydramnios.


What Are The Causes Of Polyhydramnios?

Often no cause for the polyhydramnios is found. Sometimes it is caused by the mother having diabetes in pregnancy which causes the baby to have higher blood sugar levels and therefore pass sugar into their urine which in turn causes them to pass extra urine. Very occasionally the excess fluid is caused because the baby is unable to swallow properly: normally the food pipe (oesophagus) connects to the stomach allowing the swallowed urine to pass into the digestive system of the baby. If the oesophagus does not connect to the stomach and instead the pipe is closed at the end, then the baby is unable to swallow the fluid properly and the fluid builds up; this condition is called oesophageal atresia. Oesophageal atresia can sometimes be associated with a connection between the food pipe and the breathing pipe (trachea), that condition is caused a tracheo-oesophageal fistula. If the baby has oesophageal atresia or a tracheo-oesophageal fistula, then there is a risk that they will breathe in milk when they start feeding as they are unable to swallow it properly.


What tests will my child need?

If you have been found to have a mild case of polyhydramnios, then your baby will be observed feeding by the midwifery team to ensure that they are able to feed properly without choking. If you have been found to have moderate or severe polyhydramnios, then the baby will need to have a small tube passed from their nose into their stomach (nasogastric tube) to check that the food pipe is properly connected to their stomach.

The tube should be inserted before the baby has their first feed to ensure there is no risk of them breathing in milk during the first feed. The tube will need to be inserted by one of the neonatal nurses who will come to the post natal ward to do this. Once the tube has been inserted, the nurses will connect a syringe to the end of the tube and try and extract some of the stomach contents so that they can check that this is acidic enough to prove that the tube has reached the stomach. The tube can then be removed and the baby allowed to feed normally. If the fluid doesn’t test as being acidic enough, then the baby will need to have an x-ray of their chest to confirm that the tube is in the correct place. Once this has happened the tube can be removed and the baby fed normally. If you have had mild polyhydramnios and there are any concerns about the baby’s swallowing (vomiting lots of feeds, choking or coughing during feeding) then the baby should also have a nasogastric tube inserted before feeding is continued to check there are no problems.

What is the treatment for Oesophageal Atresia or Tracheo-oesophageal Fistula?

If your baby is found to have either of these conditions, they will need to be admitted to the neonatal unit and they will not be allowed to drink milk. They will be started on a fluid drip and will need to be transferred to another hospital, (usually the John Radcliffe in Oxford), in order to be reviewed by the surgical team who will be able to advise about when they will be able to repair the condition.