What you need to know about the pregnancy complication called polyhydramnios



You might have learnt about a condition called oligohydramnios. The amniotic fluid measures lower than expected for a baby’s gestational age.

But what happens if there is too much amniotic fluid? The medical term for excess amniotic fluid is polyhydramnios.

Approximately 1% of women will be diagnosed with excessive amniotic fluid levels (polyhydramnios). Mild polyhydramnios accounts for about 65% to 70% of cases, and most women don’t have any symptoms.

It’s usually a gradual build of amniotic fluid during the second half of your pregnancy, and you will likely be able to carry your baby to full term without complications. It’s not unusual for mild polyhydramnios to resolve without treatment.

Most women don’t have any symptoms of polyhydramnios. Still, if the excess fluid causes the uterus to push up against the lungs and abdominal organs, it can cause shortness of breath and discomfort.

These symptoms are common discomforts of pregnancy, so regular prenatal care is essential for your peace of mind and rule out complications.

Treatment of polyhydramnios will depend on what is causing the higher levels of fluids, how close you are to full term, and if your baby is healthy.

The earlier polyhydramnios occurs in pregnancy, the greater the amount of excess amniotic fluid, the higher the risk of complications.

The cause of polyhydramnios is unknown in 60% – 70% of cases but the most common causes of polyhydramnios are:

1. Diabetes during pregnancy. This causes your baby’s blood sugar to be higher than usual, resulting in excessive urine. Fetal urine is the primary source of amniotic fluid.

2. Fetal anomalies affect your baby’s ability to swallow or alter kidney function. Both these functions regulate the amount of amniotic fluid in the uterus.

3. Rh factor incompatibility. This mismatch between the mother’s and baby’s blood can cause excessive amniotic fluid.

4. Twin-to-twin transfusion syndrome (TTTS). This occurs in identical twin pregnancy when one identical twin has too much blood flow, and the other has too little.

5. Intrauterine infections. The amount of amniotic fluid measures your baby’s well being and is calculated during ultrasound scans.

In a normal pregnancy, you will usually have at least 3 or 4 scans, and the amniotic fluid levels will be measured each time.

Using the standard assessment method, an average amniotic fluid index (AFI) is 5 cm to 25 cm.

Mild polyhydramnios is characterised by an AFI of 24.0 to 29.9 cm, moderate polyhydramnios by 30.0 to 34.9 cm, and severe polyhydramnios b≥ 35 cm.

The main concern for women who have polyhydramnios is the increased likelihood of the following:

  • Premature labour – going into labour too early.
  • Premature rupture of membranes – water breaking before term.
  • Placenta detaching from the uterus (placental abruption) before the birth of baby
  • Increased risk of excessive bleeding after giving birth – postpartum haemorrhage.
  • Umbilical cord prolapse – when the cord comes out before the baby.
  • Baby laying in the wrong position in the womb (fetal malposition)
  • Baby being born without signs of life (stillbirth)
  • Being told you have more amniotic fluid than usual can be frightening.

Talk to your care provider about your options and ensure you are well informed. If your symptoms increase and you are close enough to full term (or if your baby isn’t coping), your care provider will likely recommend labour induction in a hospital.

Induction of labour is associated with higher interventions, so you must be provided with all the necessary information to decide on your care.

Regular prenatal appointments are essential to monitoring your overall health, including amniotic fluid levels.

Every test and investigation in pregnancy gives information that informs your treatment plan. If you’re concerned, it’s always best to give your doctor a call.

Recommended for you