**Core Concept**
Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the presence of antiphospholipid antibodies, leading to thrombosis and pregnancy complications. The syndrome involves the activation of the coagulation cascade, platelet activation, and endothelial damage.

**Why the Correct Answer is Right**
APS is associated with a hypercoagulable state, which increases the risk of thrombosis. The antiphospholipid antibodies bind to phospholipid-binding proteins, such as beta-2 glycoprotein I, and activate the coagulation cascade through the intrinsic pathway. This leads to the formation of thrombin and fibrin, resulting in thrombosis.

**Why Each Wrong Option is Incorrect**
* **Option A:** While APS is associated with thrombosis, it is not exclusively linked to arterial thrombosis. Venous thrombosis, particularly deep vein thrombosis, is also a common manifestation.
* **Option B:** Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that can coexist with APS, but it is not a direct cause of APS.
* **Option C:** Pregnancy complications, such as recurrent miscarriage and fetal growth restriction, are a hallmark of APS. This is due to the antiphospholipid antibodies' ability to induce placental thrombosis and endothelial damage.

**Clinical Pearl / High-Yield Fact**
APS is often misdiagnosed as a primary thrombophilic disorder, such as factor V Leiden or protein C deficiency. However, APS is a distinct entity that requires a specific diagnostic approach, including the presence of antiphospholipid antibodies and clinical manifestations.

**Correct Answer: D**