Polyhydraminos

Amniotic Fluid Index

 

The amount of amniotic fluid has a certain range of normal values, the numbered score derived by adding up the centimeters of depth of four pockets of fluid seen on ultrasound. Some researchers feel one good pocket of 3 centimeters depth is enough to assume that there is adequate amniotic fluid around the rest of the baby. But the Amniotic Fluid Index(AFI) is traditionally the addition of the four pockets, with the normal range from 8 to about 18.

 

Most of the fluid in amniotic fluid is contributed to by fetal urine. This is then resorbed by the membranes and umbilical cord.  So it's possible to have differing amounts of amniotic fluid from one day to the next, even from one hour to the next. The Amniotic Fluid Index (AFI) can be used to determine fetal well-being. It is part of the more complete "Biophysical Profile" to assess whether a baby's in danger or not.  A normal AFI is about 12. But 8-18 is normal, too.

 

Definition

 

Polyhydramnios is defined as a state where liquor amnii exceeds 2000 ml or when AFI is more than 24-25 cm or a single pocket of amniotic fluid is greater than 8 cm by ultrasonography. It is seen in 0.5 to 5% of pregnancies.

 

Causes

•Maternal (15%)

·         About 20% of cases are due to maternal diabetes mellitus, which causes fetal hyperglycemia and resulting polyuria (fetal urine is a major source of amniotic fluid).

·         In a multiple gestation pregnancy, the cause of polyhydramnios usually is twin-twin transfusion syndrome.

·         It can also be caused by some systemic medical conditions in the mother, including cardiac or kidney problems.

•Fetal (18%)

·         About another 20% of cases are associated with fetal anomalies that impair the ability of the fetus to swallow (the fetus normally swallows the amniotic fluid).

·         Gastrointestinal abnormalities such as esophageal atresia, duodenal atresia, facial cleft, neck masses, and tracheoesophageal fistula

·         Fetal renal disorders that results in increased urine production during  pregnancy

·         chromosomal abnormalities such as Down's syndrome and Edwards syndrome (which is itself often associated with GI abnormalities)

·         neurological abnormalities such as anencephaly, which impair the swallowing reflex

•Placental (less than 1%)

·         Placental chorioangioma

·         Circumvallate placental syndrome

•Idiopathic (65%)

•      60-65% of cases it is unknown why polyhydramnios happens.

 

Clinical types

·         Acute Polyhydramnios: Onset is acute usually occurs before 20 weeks of pregnancy and presents usually with symptoms and labour starts before 28 weeks of pregnancy.

Symptoms:

§  Acute abdomen - abdominal pain, nausea, vomiting

§  Breathlessness which increases on lying down position

§  Palpitation

§  Edema of legs, varicosities in legs, vulva and hemorroids

Signs:

§  Patient looks ill, with out features of shock

§  Oedema of legs with signs of PIH

§  Abdomen unduly enlarged with shiny skin

§  Fluid thrill may be present

Internal examination shows taking up of cervix or even dilatation with bulging membranes

 

·         Chronic Polyhydramnios: 10% more common than acute.

Since accumulation of liquor is gradual and so patient may be symptomatic or asymptomatic.

Symptoms are mainly due to mechanical causes

§  Dyspnoea is more in supine position

§  Palpitation

§  Oedema

§  Oliguria may result from ureteral obstruction by enlarged uterus

§  Pre-eclampsia 25 %( oedema, hypertension and proteinuria)

Signs

§  Patient may be dyspnoic at rest

§  Pedal Oedema

§  Evidence of PIH

 

Abdominal examination

•        Inspection

§  Abdomen is markedly enlarged globular with fullness in flanks

§  Skin over the abdomen is tense shiny with large striae

•        Palpation

§  Height of uterus is more than the corresponding periods of Amenorrhoea

§  Abdominal girth is more

§  Fetal parts cannot be well defined external ballotment is more easily elicited

§  Malpresentations are more common and presenting part is usually high up

§  Fluid thrill is present

•        Auscultation

§  Fetal heart sounds are not heard distinctly

 

•        Internal examination :

§  Cervix is pulled up

§  May be sometimes dilated and admits tip of finger through which bag of membranes which is tense is felt.

 

Treatment

Polyhydramnios treatment includes careful monitoring of the condition, with delivery as soon as the pregnancy comes to term. If necessary, amniotic fluid levels may be lowered with medication to decrease fetal urine output, or by means of amnioreduction, a process in which a needle is inserted through the uterus to drain amniotic fluid.

 

Complications

o   Pre ecclampsia

o   PROM

o   Preterm labour

o   Placental abruption

o   Cord prolapse