Polyhydramnios
Encyclopedia
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,,. It is typically diagnosed when the amniotic fluid index (AFI) is greater than 20 cm ( ≥ 20 cm),
The opposite to polyhydramnios is oligohydramnios
, a deficiency in amniotic fluid.
, 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:
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.
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.
, 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.
Amniotic fluid
Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...
in the amniotic sac
Amniotic sac
The amniotic sac is the sac in which the fetus develops in amniotes. It is a tough but thin transparent pair of membranes, which hold a developing embryo until shortly before birth. The inner membrane, the amnion, contains the amniotic fluid and the fetus. The outer membrane, the Chorion,...
. It is seen in 0.2 to 1.6% of pregnancies,,. It is typically diagnosed when the amniotic fluid index (AFI) is greater than 20 cm ( ≥ 20 cm),
The opposite to polyhydramnios is oligohydramnios
Oligohydramnios
Oligohydramnios is a condition in pregnancy characterized by a deficiency of amniotic fluid. It is the opposite of polyhydramnios.-Diagnosis:Diagnosis is made by ultrasound measurement of the amniotic fluid index...
, a deficiency in amniotic fluid.
Causes
A single case of polyhydramnios may have one or more causes. About 14% of cases are due to maternal diabetes mellitusDiabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
, which causes fetal hyperglycemia
Hyperglycemia
Hyperglycemia or Hyperglycæmia, or high blood sugar, is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a glucose level higher than 13.5mmol/l , but symptoms may not start to become noticeable until even higher values such as 15-20 mmol/l...
and resulting polyuria
Polyuria
Polyuria is a condition usually defined as excessive or abnormally large production or passage of urine . Frequent urination is sometimes included by definition, but is nonetheless usually an accompanying symptom...
(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 atresiaEsophageal atresiaEsophageal atresia is a congenital medical condition which affects the alimentary tract. It causes the esophagus to end in a blind-ended pouch rather than connecting normally to the stomach. It comprises a variety of congenital anatomic defects that are caused by an abnormal embryological...
, duodenal atresiaAtresiaAtresia is a condition in which a body orifice or passage in the body is abnormally closed or absent.Examples of atresia include:* Imperforate anus - malformation of the opening between the rectum and anus....
, facial cleft, neck masses, and tracheoesophageal fistula - fetal renal disorders that results in increased urine production during pregnancy, such as in antenatal Bartter syndromeBartter syndromeBartter syndrome is a rare inherited defect in the thick ascending limb of the loop of Henle. It is characterized by low potassium levels , increased blood pH , and normal to low blood pressure. There are two types of Bartter syndrome: neonatal and classic...
. Molecular diagnosis is available for these conditions. - chromosomal abnormalities such as Down's syndromeDown syndromeDown syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
and Edwards syndromeEdwards syndromeTrisomy 18 is a genetic disorder caused by the presence of all or part of an extra 18th chromosome. It is named after John H. Edwards, who first described the syndrome in 1960...
(which is itself often associated with GI abnormalities) - neurological abnormalities such as anencephalyAnencephalyAnencephaly is a cephalic disorder that results from a neural tube defect that occurs when the cephalic end of the neural tube fails to close, usually between the 23rd and 26th day of pregnancy, resulting in the absence of a major portion of the brain, skull, and scalp...
, 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
Twin-to-twin transfusion syndrome
Twin-to-twin transfusion syndrome is a complication of disproportionate blood supply, resulting in high morbidity and mortality. It can affect monochorionic multiples, that is multiple pregnancies where two or more fetuses share a chorion and hence a single placenta...
.
It can also be caused by some systemic medical conditions in the mother, including cardiac or kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
problems.
it can also be caused by intrauterine infection (TORCH
TORCH complex
TORCH complex is a medical acronym for a set of perinatal infections . The TORCH infections can lead to severe fetal anomalies or even fetal loss...
)
Additionally, chorioangioma of the placenta
Angioma
Angiomas are benign tumors derived from cells of the vascular or lymphatic vessel walls or derived from cells of the tissues surrounding these vessels....
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 prolapseCord prolapse
Umbilical cord prolapse happens when the umbilical cord precedes the fetus' exit from the uterus. It is an obstetric emergency during pregnancy or labor that imminently endangers the life of the fetus. Cord prolapse is rare...
, placental abruption
Placental abruption
Placental abruption is a complication of pregnancy, wherein the placental lining has separated from the uterus of the mother. It is the most common pathological cause of late pregnancy bleeding. In humans, it refers to the abnormal separation after 20 weeks of gestation and prior to birth...
, 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 nauseaNauseaNausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
. - Dietary salt restriction is recommended.
- In some cases, amnioreduction, also known as therapeutic AmniocentesisAmniocentesisAmniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for...
, has been used in response to polyhydramnios.