The major contribution of amniotic fluid after 20 weeks of gestation :
Origin of amniotic fluid : Early week -Maternal plasma 2 nd trimester - Fetal skin Beyond 20 weeks -Fetal urine Ref: Datta Obs 9e pg 34.
Ultrafiltrate and maternal plasma
Fetal urine
Fetal lung fluid
Fetal skin
General obstetrics