Polyhydramnios

PolyhydramniosDr. Agus Rusdhy Hariawan Hamid,SpOG

Polyhydramnios is the pathologic accumulation of excessive quantities of amniotic fluid. When polyhydramnios is diagnosed, a thorough examination for underlying abnormalities is indicated and the risk of adverse pregnancy outcome is increased.

While the presence of polyhydramnios may be idiopathic, it should alert the physician that congenital or chromosomal anomalies may be present. Because pregnancies complicated by polyhydramnios are at significantly increased risk for perinatal mortality and other complications, heightened surveillance and monitoring, as well as possible interventions must be considered.

Polyhydramnios complicates approximately 1% of pregnancies.The amniotic fluid volume (AFV) increases from early in pregnancy until term.The AFV is kept in balance by fetal micturation, pulmonary secretions, and fluid passing through membranes. As pregnancy progresses, AFV constitutes a decreasing portion of the total uterine volume. It may represent 50% at 16 weeks gestation but only 17% at term. Normal AFVs generally increase from early pregnancy until approximately 3638 weeks gestation, at which time the maximum volume may be 1.01.5 L. As the pregnancy approaches term, the volume may decrease, which continues as the pregnancy goes past term.

The pathophysiology of polyhydramnios is dependent on the underlying abnormality. In pregnancies complicated by diabetes, maternal hyperglycemia results in fetal hyperglycemia and increased fetal micturation. When there are anatomic abnormalities, such as esophageal atresia, fetal swallowing is impaired and may result in polyhydramnios. Multiple gestations are at increased risk for polyhydramnios resulting from twintwin transfusion syndrome.Pregnancies complicated by abnormalities of the central nervous system (CNS), such as anencephaly, neural tube defects, or substance abuse,may have polyhydramnios from CNS depression.Neuromuscular disorders with impaired fetal swallowing may also result in polyhydramnios. Fetal anemia, caused by Rh-isoimmunization, parvovirus infection, or fetalmaternal hemorrhage, may cause polyhydramnios through increased cardiac output.