Okay, let's tackle this question about uteroplacental circulation. The question is asking which statement is NOT true. First, I need to recall the key points about uteroplacental circulation.

Uteroplacental circulation involves the blood flow from the mother to the placenta and back. The main arteries involved are the uterine arteries, which branch into spiral arteries. The placenta's blood supply is crucial for nutrient and gas exchange between mother and fetus.

The question is about an exception, so I need to think of common misconceptions or incorrect statements. Let me consider possible options. For example, one might think that the blood flow is continuous, but in reality, it's intermittent. Also, the resistance in the uterine arteries decreases as pregnancy progresses, which is important for maintaining placental perfusion. Another point is that the placental blood is not filtered by the placenta, so fetal and maternal blood mix minimally.

If an option states that the placental blood flow is high resistance, that's incorrect because resistance actually decreases. Or if someone says that the maternal blood flows directly into fetal circulation, which is false because it's separated by the placental barrier. Also, maybe an option about the oxygen saturation levels in maternal vs fetal blood. Maternal blood has higher oxygen, but fetal blood has lower, so if an option says the opposite, that's wrong.

Wait, the correct answer is the one that's incorrect. So I need to list the options. But the user hasn't provided them. Hmm, maybe the original question had options that weren't included here. Let me think of common distractors. For example, a wrong statement could be that the placental circulation has high resistance, which is false because resistance decreases. Another could be that maternal blood is directly mixed with fetal blood, which is incorrect. Or maybe about the percentage of cardiac output to the placenta. In late pregnancy, about 500-700 mL/min goes to the placenta, which is around 10-15% of maternal CO. If an option says it's 20-30%, that's incorrect.

So the core concept here is understanding the hemodynamics of uteroplacental circulation. The correct answer would be the statement that contradicts this. For example, if an option states that uterine artery resistance increases during pregnancy, that's wrong because it decreases. Another wrong option could be that the placental blood flow is continuous, but it's actually pulsatile. Also, the placenta doesn't have a capillary bed; instead, the intervillous spaces hold the maternal blood.

Putting this together, the most likely incorrect statement would be about high resistance in uterine arteries. So if an option says that, it's the exception. Therefore, the correct answer would be the option stating high resistance in uterine arteries during pregnancy.

**Core Concept**
Uteroplacental circulation refers to blood flow between maternal uterine arteries and placental intervillous spaces. Key features include low vascular resistance, high blood flow (10-15% of maternal cardiac output), and absence of a capillary bed in the placenta. Understanding these hemodynamics is critical for assessing placental function and fetal-maternal exchange.

**Why the Correct Answer is Right**
The incorrect statement likely involves **increased vascular resistance** in ut

✓ Correct Answer: C. A mature placenta has 150 ml of blood in the villi system and 350 ml of blood in the intervillous space