Polyhydramnios

Polyhydramnios (polyhydramnion, hydramnios, polyhydramnios) is a medical condition describing an excess of amniotic fluid in the amniotic sac. It is seen in 0.2 to 1.6% of pregnancies,^[1][2],.^[3] It is typically diagnosed when the amniotic fluid index (AFI) is greater than 20 cm ( ≥ 20 cm),^[4][5] There are two clinical varieties of polyhydramnios:

• Chronic polyhydramnios where extra liquor accumulates gradually and it is much common variety.
• Acute polyhydramnios where excess amniotic fluid collects rapidly.

The opposite to polyhydramnios is oligohydramnios, a deficiency in amniotic fluid.

Causes

About 50%-60% of cases, the exact cause can not be identified. A single case of polyhydramnios may have one or more causes. About 14% of cases are due to maternal diabetes mellitus, which causes fetal hyperglycemia and resulting polyuria (fetal urine is a major source of amniotic fluid) and also rh-isoimmunisation can cause it. 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). These anomalies include:

• 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, such as in antenatal Bartter syndrome.^[6] Molecular diagnosis is available for these conditions.^[7]
• 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

It may also be caused by a congenital defect (a congenital diaphragmatic hernia), Bochdalek's hernia, in which the pleuro-peritoneal membranes (especially the left) will fail to develop & seal the pericardio- peritoneal canals. This results in the stomach protrusion up into the thoracic cavity, and the fetus is unable to swallow sufficient amounts 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. it can also be caused by intrauterine infection (TORCH)

Additionally, chorioangioma of the placenta can also cause this condition.

However, it should be reported that in 60-65% of cases it is unknown why polyhydramnios happens.

Diagnosis

There are several pathologic conditions that can predispose a pregnancy to polyhydramnios. These include a maternal history of diabetes mellitus, Rh incompatibility between the fetus and mother, intrauterine infection, and multiple pregnancies.

During the pregnancy, certain clinical signs may suggest polyhydramnios. In the mother, the physician may observe increased abdominal size out of proportion for her weight gain and gestation age, uterine size that outpaces gestational age, shiny skin with stria (seen mostly in severe polyhydramnios), dyspnea, and chest heaviness. When examining the fetus, faint fetal heart sounds are also an important clinical sign of this condition.

Associated conditions

Fetuses with polyhydramnios are at risk for a number of other problems including cord prolapse, placental abruption, premature birth and perinatal death. At delivery the baby should be checked for congenital abnormalities. Another cause of polyhydramnios is skeletal dysplasia, or dwarfism, in the baby. There is a possibility of the chest cavity not being large enough to house all of the baby's organs causing the trachea and esophagus to be restricted, not allowing the baby to swallow the appropriate amount of amniotic fluid.

Treatment

• Mild asymptomatic polyhydraminos is managed expectantly. For a woman with symptomatic polyhydrminos may need hospital admission. Antacids may be prescribed to relive heartburn and nausea.
• Dietary salt restriction is recommended.
• In some cases, amnioreduction, also known as therapeutic Amniocentesis, has been used in response to polyhydramnios.^[8]

See also

• Amniotic fluid index

References

1. ^ Alexander, ES, Spitz, HB, Clark, RA. Sonography of polyhydramnios. AJR Am J Roentgenol 1982; 138:343
2. ^ Hill LM; Breckle R; Thomas ML; Fries JK, Polyhydramnios: ultrasonically detected prevalence and neonatal outcome, Obstet Gynecol 1987 Jan;69(1):21-5, PMID 3540761
3. ^ Hobbins JC; Grannum PA; Berkowitz RL; Silverman R; Mahoney MJ,Ultrasound in the diagnosis of congenital anomalies.,Am J Obstet Gynecol 1979 Jun 1;134(3):331-45., PMID 453266
4. ^ Rutherford SE; Phelan JP; Smith CV; Jacobs N, The four-quadrant assessment of amniotic fluid volume: an adjunct to antepartum fetal heart rate testing., Obstet Gynecol 1987 Sep;70(3 Pt 1):353-6.
5. ^ Clinical Management Guidelines for Obstetrician-Gynecologists, Number 55, September 2004.
6. ^ Seyberth HW. (2008). "An improved terminology and classification of Bartter-like syndromes.". Nat Clin Pract Nephrol. 4 (10): 560–7. doi:10.1038/ncpneph0912. PMID 18695706. 
7. ^ http://www.moldiag.de/en/dis/bartter.htm
8. ^ Piantelli G, Bedocchi L, Cavicchioni O, et al. (2004). "Amnioreduction for treatment of severe polyhydramnios". Acta bio-medica : Atenei Parmensis. 75 Suppl 1: 56–8. PMID 15301292. 

External links

• 00329 at CHORUS