Polyhydramnios

Introduction

• It is a condition where liquor amnii is in excessive amount i.e. > 2 liters. 
• The most commonly used definition is by ultrasound assessment, i.e. when the amniotic fluid index (AFI) is > 25 cms or finding a pocket of fluid measuring 8 cm or more in vertical diameter.

Grades of Polyhydramnios

1. Mild defined as pockets measuring 8-11 cm in the vertical dimension (seen in 80% cases).
2. Moderate defined as pocket measuring 12-15 cm in the vertical dimension (seen in 15% cases).
3. Severe defined as free-floating fetus found in pockets of fluid of 16 cm or more (seen in 5% cases).

Causes of Polyhydramnios

• The main contributor of amniotic fluid is fetal urine.
• Amount of amniotic fluid will be more (i.e. polyhydramnios) if:

1. Fetus produces more urine for example:

a. Twin/multifetal pregnancy (number of the fetus is more: more of urine)

b. Maternal hyperglycemia/diabetes Maternal hyperglycemia →Fetal hyperglycemia → Fetalpolyuria →increased amniotic fluid.

c. Twin to Twin transfusion syndrome.

2. Besides producing Amniotic fluid fetus also swallows amniotic fluid. 

→The amount of amniotic fluid will increase if; fetal swallowing is impaired as in case of:

a. Cleft lip and cleft palate

b. Esophageal atresia or stenosis

c. Duodenal atresia or stenosis

d. Bowel obstruction

e. Anencephaly (swallowing is decreased + increased transudation of CSF into amniotic fluid due to absence of cranial vault)

3. Other important causes of polyhydramnios are:

Placental Causes

a. Chorangioma of the placenta and circumvallate placenta.

Fetal Causes

a. Hydrops fetalis

b. Rubella, syphilis, Toxoplasma infection of the fetus.

c. Trisomy (note – Triploidy leads to oligohydramnios)

d. Sacrococcygeal Teratoma

e. Thalassemia of the fetus.

 

• M/C cause of mild polyhydramnios: idiopathic
• M/C cause of severe polyhydramnios: Gross congenital anomaly i.e. GIT malformations> CNS malformations.

Clinical Features

→Symptoms:

• Respiratory: dyspnea
• Palpitation
• Edema of the legs, varicosities in the legs or vulva and hemorrhoids

→Signs:

• Evidence of preeclampsia (edema, hypertension, and proteinuria)

Abdominal Examination:

→Inspection:

• Abdomen enlarged, Globular with fullness at flanks.
• Skin is tense, shiny with large striae

→Palpation:

• ↑Height of the uterus
• The girth of the abdomen around the umbilicus is more than normal
• Fluid thrill 
• Fetal parts cannot be well-define
• Auscultation: FHS is not heard distinctly

Investigations:

→Sonography:

• Detect abnormally large echo-free space
• largest vertical pocket more than 8 cm
• AFI is more than 25 cm
• Exclude multiple fetuses
• Detect lie and presentation of the fetus
• Diagnose any fetal congenital malformation

→Blood:

• ABO and Rh grouping
• Postprandial sugar and if necessary glucose tolerance test.

→Amniotic Fluid:

• Estimation of alpha-fetoprotein markedly elevated in the presence of a fetus with an open neural tube defect.

→maternal diagnostic testing for infection (TORCH serology)

Complications

→Maternal

• Due to excessive fluid membranes are overstretched so it can lead to premature rupture of membranes (PROM) and preterm labor.
• Abruptio placenta
• PPH (due to overstretching & tone of uterus decreases)
• Subinvolution of uterus
• PIH (25% cases)
• Cord prolapse
• Malpresentation
• Unstable lie

→In Fetus = Due to prematurity and congenital anomalies, there is increased perinatal mortality.

Management

Mild Polyhydramnios (DVP: 8–11 cm):

• Midtrimester
• No treatment 

Severe Polyhydramnios (DVP: >16 cm):

Supportive therapy

• Sulindac
• bed rest

Further management depends on

• Response to treatment 
• Period of gestation
• Presence of fetal malformation 
• Associated complicating factors.

1)       Serial amniocentesis is the TOC ( treatment of choice) if the patient is in distress (Remember: Amount of fluid removed is 500 ml/hr, maximum up to 1500-2000 mL).

2)       Indomethacin therapy is an alternative management. It acts by decreasing fetal urinary output and by increasing reabsorption of fluid via the lungs.

• Dose: 1.5-3 mg/kg/day.
• The potential hazard of Indomethacin therapy – Premature closure of fetal ductus arteriosus. 
• So, the therapy should be stopped at 32 weeks.

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