**Core Concept**
The postpartum period is a crucial time for sterilization in patients with cardiovascular disease due to the increased risk of thromboembolic events. The ideal time for postpartum ligation of the fallopian tube is when the risk of these complications is minimized.

**Why the Correct Answer is Right**
The optimal time for postpartum ligation in patients with heart disease is between 6-12 weeks post-delivery. During this period, the risk of thromboembolic events has decreased, and the patient's cardiovascular system has had time to recover from the stresses of pregnancy and delivery. This timeframe also allows for adequate healing of the uterine incision site, reducing the risk of complications associated with the procedure.

**Why Each Wrong Option is Incorrect**
**Option A:** Immediate postpartum ligation is not recommended in patients with heart disease due to the increased risk of thromboembolic events and complications associated with the procedure.
**Option B:** Ligation performed too early, such as within the first few days postpartum, may not allow for adequate healing of the uterine incision site, increasing the risk of complications.
**Option C:** Performing ligation too late, such as after 6 months postpartum, may not be feasible due to the patient's potential return to fertility and the increased risk of complications associated with a delayed procedure.

**Clinical Pearl / High-Yield Fact**
When considering postpartum sterilization in patients with cardiovascular disease, it is essential to weigh the risks and benefits of the procedure, taking into account the patient's individual cardiovascular risk factors and the timing of the procedure.

**Correct Answer:** C. 6-12 weeks post-delivery.