Anemia of Prematurity - Portal Neonatal

Polyhydramnios and Oligohydramnios
Last Updated: June 10, 2002
Synonyms and related keywords: too much amniotic fluid, too little amniotic fluid, oligoamnios,
oligamnios, fetal lung development, membrane rupture, fetal urine, fetal swallowing, Potter syndrome
AUTHOR INFORMATION Section 1 of 9
Author: Roland L Boyd, DO, FAAP, FACOP, Neonatologist, Section of Neonatology, MCG
Coauthor(s): Brian S Carter, MD, Associate Director, Associate Professor, Department of
Pediatrics, Division of Neonatology, Vanderbilt University Medical Center
Roland L Boyd, DO, FAAP, FACOP, is a member of the following medical societies: American
Academy of Osteopathy, American Academy of Pediatrics
Editor(s): Ted Rosenkrantz, MD, Head, Division of Neonatal Perinatal Medicine, Professor,
Department of Pediatrics, University of Connecticut Health Center; Robert Konop, PharmD,
Director, Clinical Account Management, Ancillary Care Management; David A Clark, MD,
Chairman, Professor, Department of Pediatrics, Albany Medical College; Carol L Wagner, MD,
Associate Professor, Department of Pediatrics, Division of Neonatology, Medical University of South
Carolina; and Neil N Finer, MD, Director, Division of Neonatology, Professor, Department of
Pediatrics, University of California at San Diego
INTRODUCTION Section 2 of 9
Background: The amniotic fluid that bathes the fetus is necessary for its proper growth and
development. It cushions the fetus from physical trauma, permits fetal lung growth, and provides a
barrier against infection. Normal amniotic fluid levels vary; however, the average volume increases
with gestational age, peaking at 800-1000 mL, which coincides with 36-37 weeks' gestation. An
abnormally high level of amniotic fluid, polyhydramnios, alerts the clinician to possible fetal
anomalies. Inadequate levels of amniotic fluid, oligohydramnios, results in poor development of the
lung tissue and can lead to fetal death.
In pregnancies affected by polyhydramnios, approximately 20% of the neonates are born with a
congenital anomaly of some type; therefore, the delivery of these newborns in a tertiary care setting
is preferred. This article presents the causes, outcomes, and treatments of polyhydramnios and
oligohydramnios, as well as their effects on the developing fetus and neonate.
Pathophysiology: Rupture of the membranes is the most common cause of oligohydramnios.
However, because the amniotic fluid is primarily fetal urine in the latter half of the pregnancy, the
absence of fetal urine production or a blockage in fetus' the urinary tract also can result in
oligohydramnios. Fetal swallowing, which occurs physiologically, reduces the amount of fluid, and an
absence of swallowing or a blockage of the fetus' gastrointestinal tract can lead to polyhydramnios.
Frequency: In the US: Oligohydramnios occurs in 4% of pregnancies, and polyhydramnios occurs
in 1% of pregnancies.
Mortality/Morbidity:
• Chamberlin used ultrasonography to evaluate the perinatal mortality rate (PMR) in 7562
patients with high-risk pregnancies. The PMR of patients with normal fluid volumes was 1.97
deaths per 1000 patients. The PMR increased to 4.12 deaths per 1000 patients with
polyhydramnios and 56.5 deaths per 1000 patients with oligohydramnios
• Preterm labor and delivery occurs in approximately 26% of mothers with polyhydramnios.
Other complications are premature rupture of the membranes (PROM), abruptio placenta,
malpresentation, cesarean delivery, and postpartum hemorrhage