This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Gynae), Subject name: Gynaecology & Obstetrics
[{'content': 'The major contribution of the ammiotic fluid after 20 weeks of gestations \nSelect and explain. \nA. Ultrafiltrate and maternal plasma, B. Foetal urine, C. Foetal lung fluid, D. Foetal skin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: (Foetal urine): Ref: 37, 214, 218, 464-D Obstetrics - G. Chamberlain 7thAMNIOTIC FLUIDProduced: In early pregnancy, from amnion over placenta and sacLate pregnancy: from fetal urine as wellVolume: Increase to 38 weeks (500 - 1500 ml)50 ml: 12 weeks500 ml: 24 weeks1000 ml: 36 weeksOsmolality: Decreases in late pregnancyCreatinine: Increases in late pregnancyAcid - base: Normally accumulation of CO2 and fixed acid causes a slight reduction in pH (About 7.15 - 7.20)* The foetus drinks about 400 ml of liquer every day at term and equal amount is excreted in the urine* The water in the amniotic fluid is completely changed and replaced in every 3 hours.* Abnormal colour- Meconium stained (green) - Foetal distress Breech or transverse- Golden colour - Rh. Incompatibility- Greenish yellow (Saffron) - Post maturity- Dark coloured - concealed accidental hemorrhage- Dark brown (tobacco juice) - IUD* Amniotic Fluid Index (AFI) - An AFI between 5 and 25 cm is normal and an AFI less than 5 cm (< 10 centile) indicates oligohydramnios and AFI more than 25 cm (> 95 centile for gestational age) indicates Polyhydramnios (464-D)', 'role': 'assistant'}]