Chapter 11: Disorders of Amnionic Fluid Flashcards
Amniotic fluid volume increase
30 mL at 10 weeks
200 mL by 16 weeks
800 mL by the mid-third trimester
Amniotic fluid composition
98% water
Abnormally decreased fluid volume
Oligohydrmanios
Abnormally increased fluid volume
hydramnios or polyhydramnios
(First half of pregnancy) Transfer of water and other small molecules
across amnion
transmembranous flow
(First half of pregnancy) Transfer of water and other small molecules
across the fetal vessels on placental surface
intramembranous flow
(First half of pregnancy) Transfer of water and other small molecules
across fetal skin
transcutaneous flow
until keratinisation at 22 to 25 weeks
Fetal urine production begin
8 and 1 1 weeks’ gestation
when does lethal renal abnormalities manifests
after 1 8 weeks
Fetal urine osmolality
equal to amniotic fluid
hypotonic to maternal and fetal plasma
Amniotic fluid volume regulation late pregnancy
Fetal urination
production
Amniotic fluid volume regulation late pregnancy
Fetal swallowing
Resorption
Amniotic fluid volume regulation late pregnancy
Fetal lung fluid secretion
Production
Amniotic fluid volume regulation late pregnancy
intramembranous flow across the fetal vessels on placental surface
Resorption
Amniotic fluid volume regulation late pregnancy
transmembranous flow across amniotic membrane
Resorption
Measurement: dye dilution
aminohippurate
Mean value (22-39 wks)
750ml
Normal Single deepest pocket
> 2cm
<8cm
Normal AFI
> 5cm
<25 cm
Mild Hydramnios
AFI 25 to 29.9 cm
SDP 8 to 9.9 cm
Moderate Hydramnios
AFI 30 to 34.9 cm
SDP 10 to 11.9 cm
Severe
AFI 35 cm or more
SDP 12 cm or more
Etiology of hydramnios
- fetal anomalies:
structural abnormalities or genetic syndromes , and diabetes - Congenital infection: cytomegalovirus, toxoplasmosis, syphilis, and parvovirus
- red blood cell alloimmunization
- placental chorioangioma
-hydrops fetalies
Pathophysiology: hydramnios with diabetes
maternal hyperglycemia causes fetal hyperglycemia, with resulting fetal osmotic diuresis into the amniotic fluid compartment
Diagnostic criteria for twin-twin transfusion syndrome (TTTS)
Monochorionic gestations, hydramnios of one sac and oligohydramnios of the other
Hydramnios complication
Maternal
-uterine Distention
- Dyspnea and orthopne
- Edema - lower extremities, vulva, and abdominal wall
- placental abruption, uterine dysfunction during labor, and postpartum hemorrhage
fetal
-membrane rupture or therapeutic amnioreduction
Oligohydramnios ethology
- fetal abnormality
- placental abnormality suciently severe —> impair perfusion
- Rule out ruptured membrane
Oligohydramnios Congenital anomalies (renal)
bilateral renal agenesis
bilateral multicystic dysplastic kidney
unilateral renal agenesis with contralateral multicystic dysplastic kidney
infantile form of autosomal recessive poycystic kidney disease
Oligohydramnios Congenital anomalies (genitourinary)
persistent cloaca and sireno melia
Drugs causing oligohydramnios
ACEi
ARBs
Effects: fetal hypotension renal hypoperfusion renal ischemia anuric renal failure
NSAIDs
Effects:
acute and chronic renal insuciency
Fetal skull bone hypoplasia and limb contractures
Oligohydramnious outcome
stillbirth
preterm birth
heart rate pattern abnormalities
growth restriction
Oligohydramnios management
close fetal surveillance
maternal hydration
