AMNIOTIC FLUIDBy: Ola S. Eldardiry

Introduction

Embryology

Embryology

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

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)

Composition

Composition + volume changes as pregnancy advances

In the 1st ½ of pregnancy, fluid is same as ECF of foetus, devoid of particulate mattero 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

• 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)

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

Assessment

SDVPAFI

SDVP

Measurement of deepest, cord-free, devoid of foetal parts,

vertical pocket

Normal range: 2–8 cm

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