This document discusses amniotic fluid, including its: - Volume, which increases to around 1000 ml by 36-38 weeks gestation before decreasing. - Circulation and constituents, which originate from both the mother and fetus through processes like transudation, secretion, swallowing, and fetal urination. - Composition, which changes with gestation and includes water, electrolytes, urea, and other substances from the fetus. - Functions in allowing fetal movement, aiding lung and bone development, maintaining temperature, and protecting the fetus. - Assessment methods like measuring the single deepest vertical pocket (SDVP) and amniotic fluid index (AFI).

1. AMNIOTIC FLUID
By: Ola S. Eldardiry

2. Introduction

3. Embryology

4. Embryology

5. Volume
• About 500 ml enter and
leave the amniotic sac each
hour.
• Gradual  up to 36 wks to
around 600-1000 ml then 
after that.
• Normal range is wide but
approx. volumes are:
 50 ml 12 wks
 400 ml 20 wks
 800 ml 34 wks
 1000 ml 36-38 wks
 At full term, there is
between 600-800 cc of AF

6. Circulation and Constituents
• Origin: Maternal + Foetal
a) Simple transudation from maternal
blood into placental sinuses
b) Active secretion by chorion and
amnion
c) Foetal urine  at full term
d) Foetal skin  solid particles (vernix
caseosa) + cellular component
e) Excretions from respiratory tract
f) Alimentary canal: by swallowing
and absorption (as early as 20
wks)

8. Composition
 Composition + volume changes as pregnancy advances
 In the 1st ½ of pregnancy, fluid is same as ECF of foetus, devoid of
particulate matter
o Produced by amniotic membranes
o Fluid also passes across foetal skin
 By the 4th month, the foetus contributes to AF via:
o urinating
o swallowing
o movement of fluid in and out of the respiratory tract
o Foetal urination will eventually comprise the majority of AF
 Foetal kidneys start to develop during 4th and 5th wks of gestation and begin
to excrete urine into AF at the 11th-13th wk
 At the 20th wk fetal kidneys produce most of AF
 Foetal urine is hypotonic (c/w plasma) because of lower electrolyte
concentration
 Contains more urea, creatinine and uric acid
 Osmolality  with  gestational age

9. • An important function of foetal kidney  maintain a urine output sufficient to
maintain AF volume
• Daily urine production is approx. 30% of foetal weight
• The excreted urine does not serve real excretory or homeostatic function
because the urine, via the AF, is recycled back to the foetus by swallowing
(25% of foetal weight)

10. Function
 Allows movement of developing foetus in womb  allow
proper bone growth
 Proper development of lungs
 Maintaining relative constant temp. around baby + protection
from heat loss
 Act as cushion  protect baby from outside injury or trauma

11. Assessment
SDVPAFI

12. SDVP
 Measurement of deepest, cord-free, devoid of foetal parts,
vertical pocket
 Normal range: 2–8 cm

13. AFI
• Volume of AF is evaluated by visually dividing the
mother's abdomen into 4 quadrants
• The largest vertical pocket of fluid in each
quadrant is measured in cm
• Cord containing pocket < 30%
• Total volume is calculated by adding these values
• < 5 oligohydramnios
o AFI < 5.0 cm had a sensitivity of 18% for the detection of
oligohydramnios
• 6-8 borderline AFI
• 8-24 normal
• > 24 polyhydramnios