Polyhydramnios

Overview: 

 Polyhydramnios is too much amniotic fluid surrounding an unborn infant. The amniotic fluid is part of the baby’s life support system. It protects the baby and aids in the development of muscles, limbs, lungs and the digestive system. Amniotic fluid is produced soon after the amniotic sac forms.  In some cases the amniotic fluid may measure too low or too high. 

Doctors can measure the amount of fluid through a few different methods, most commonly through amniotic fluid index (AFI) evaluation or deep pocket measurements. If an AFI shows a fluid level of more than 25 centimeters (or above the 95th percentile), a single deep pocket measurement of <8, or a fluid level of 2000ml or more, then diagnosis of polyhydramnios would be made. 

1. Pathopysiology:

Polyhydramnios occurs due to an imbalance between amniotic fluid production and clearance. The main mechanisms include:

• Increased Production: Excessive fetal urine output from conditions like maternal diabetes or twin-to-twin transfusion syndrome.

• Decreased Clearance: Impaired fetal swallowing, often due to anomalies like esophageal or duodenal atresia, or neurological disorders.

• Idiopathic Causes: In about 50% of cases, no clear cause is identified.

Amniotic fluid volume rises above normal levels, with an AFI > 24 cm or a deepest pocket > 8 cm. This can lead to risks like preterm labor, cord prolapse, and maternal respiratory issues. Management depends on severity and underlying causes, such as glucose control or amnioreduction.

2. Treatment: 

 Many cases of polyhydramnios are easily treated and do not result in complications if the pregnancy is

monitored closely. Monitoring would include frequent sonograms measuring growth, biophysical profile

and fetal assessment. Other treatments include: 

• Medication that can reduce fluid production and are as much as 90% effective. This treatment is not

  used after 32 weeks gestation because of possible complications. 

• Amnioreduction is a procedure that can be used to drain excess fluids. This is done through amniocentesis,

  which may carry certain risks. There is, however, the chance that fluid could build back up even after draining 

• Delivery of the baby 

3. Causes: 

Congenital defects - The higher the fluid level, the increased chance of congenital defect. These birth defects hinder swallowing, which can prohibit ingestion of the amniotic fluid, resulting in buildup of fluid. Other birth defects could also include intestinal tract blockage or neurological abnormalities. 

Rh Factor - As screening for the Rh factor has increased; this is no longer a common cause of elevated fluid levels. 

Maternal Diabetes - Experts have found some correlation between diabetes and too much amniotic fluid. 

Twin-to-twin transfusion syndrome - This is complication that can affect identical twin pregnancies. This syndrome is when one baby gets too much blood flow and the other too little due to connections between blood vessels in their shared placenta. 

Unknown Reasons - According to the Center for Maternal Fetal Medicine, about 65% of cases of polyhydramnios are due to unknown causes. 

4. Prognosis:  

The risk of the following obstetric complications is increased when polyhydramnios is present due to over-expansion of the uterus. 

• Maternal dyspnea 

• Preterm labor 

• Premature rupture of membranes 

• Abnormal fetal presentation 

• Umbilical cord prolapse 

• Postpartum hemorrhage 

• Fetal macrosomia due to maternal diabetes mellitus 

• Hypertensive disorders of pregnancy 

• Urinary tract infection 

5. Complications: 

Most cases of polyhydramnios are mild and result in few, if any, complications. Those with higher levels of fluid could experience one or more of the following risks: 

• Premature rupture of membranes (PROM) 

• Placental abruption 

• Preterm labor and delivery (approximately 26%) 

• Growth restriction (IUGR) resulting in skeletal malformations 

• Stillbirth occurs in about 4 in 1000 pregnancies that suffer from polyhydramnios vs. about 2 in 1000 pregnancies with normal fluid levels. 

• Cesarean delivery 

• Postpartum hemorrhage 

What should RT’s prepare for in deliveries where the mother had polyhydramnios?

In deliveries complicated by maternal polyhydramnios, respiratory therapists (RTs) should anticipate neonatal challenges such as respiratory distress, airway anomalies, and prematurity. The excess amniotic fluid can be associated with congenital conditions like esophageal atresia, diaphragmatic hernia, or neurological abnormalities, which may impair the infant's ability to maintain effective breathing. RTs must prepare for immediate airway management, including suctioning, intubation, and ventilation support such as CPAP or mechanical ventilation, especially in cases of underdeveloped lungs. Resuscitation equipment should be readily available, with readiness to stabilize oxygenation (SpO₂ 88–94%) and address complications like hypoxia or acidosis. Collaboration with NICU teams and specialists, as well as preparation for transport if higher-level care is needed, is critical to ensure optimal outcomes for these neonates.