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.
