**Core Concept**
The management of early pregnancy complications, specifically the evaluation of a missed abortion, relies on the integration of clinical history, ultrasound findings, and biochemical markers. In this scenario, a 6-week amenorrhea with no visible gestational sac on ultrasound and a serum beta hCG level of 1000 IU/L indicates a potential missed abortion.

**Why the Correct Answer is Right**
A missed abortion is characterized by the absence of a visible gestational sac on ultrasound, despite a rising serum beta hCG level. This discrepancy suggests that the pregnancy is non-viable. In this case, a serum beta hCG level of 1000 IU/L is below the expected threshold for a 6-week gestation, further supporting the diagnosis of a missed abortion. The next step in management is to perform a dilation and curettage (D&C) to evacuate the uterus and confirm the diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Serial ultrasound evaluation is not the appropriate next step, as the ultrasound has already been performed and the findings are consistent with a missed abortion.
**Option B:** Expectant management is not indicated in this scenario, as the patient has a high risk of developing complications such as infection or hemorrhage if the pregnancy is not evacuated.
**Option C:** Medical management with mifepristone or misoprostol may be considered in some cases of missed abortion, but it is not the first-line approach in this scenario, as the patient has already reached 6 weeks of gestation and the pregnancy is likely to be more advanced.

**Clinical Pearl / High-Yield Fact**
A missed abortion is a common complication of early pregnancy, and it is essential to differentiate it from a failed medical abortion, which is a planned termination of pregnancy using medical means.

**Correct Answer:** D. Dilation and curettage (D&C).