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Chapter 18 Amniotic Fluid
Kristin Van Heertum, MD
❍ What are the five major functions of amniotic fluid?
(1) Helps to protect the fetus from trauma.
(2) Cushions the umbilical cord from compression between the fetus and uterus.
(3) Antibacterial properties that provide some protection from infection.
(4) Serves as a reservoir of fluid and nutrients for the fetus.
(5) Provides the necessary fluid, space, and growth factors to permit normal development of the fetal lungs and
musculoskeletal and gastrointestinal (GI) systems.
❍ What is the major source of amniotic fluid production in the first trimester?
An ultrafiltrate of maternal plasma—passes through the fetal membranes by osmosis and hydrostatic forces.
❍ What is the major source of amniotic fluid production in the second half of pregnancy?
Fetal urination.
❍ What other sources contribute to amniotic fluid production in the second half of pregnancy?
Secretions from the fetal respiratory tract, including the lungs and oral-nasal cavity and intramembranous flow.
❍ What is the major pathway of clearance of amniotic fluid in the last half of pregnancy?
Fetal swallowing.
❍ Significant amounts of water and solutes are not transferred across the fetal skin after keratinization occurs.
What gestational age does this occur?
Between 22 and 25 weeks gestation.
❍ When is amniotic fluid volume at its peak?
34 to 36 weeks gestation.
❍ What is the average peak of amniotic fluid volume?
1 L (1000 cc).