Final answer:
Abortions characterized by fetal demise without cervical dilation or passage of POCs are known as missed abortions, which is option C.
Step-by-step explanation:
The type of abortions that occur with fetal demise without cervical dilation or passage of products of conception (POCs) are called missed abortions.
In a missed abortion, the fetus has died or has not developed but is still retained in the uterus. This situation differs from other types of spontaneous abortions or miscarriages, such as incomplete abortion (where some but not all of the pregnancy tissue is passed), a threatened abortion (where there are symptoms that suggest a miscarriage might be imminent), and complete abortion (where all pregnancy tissue has been passed).
Therefore, the correct answer is C. Missed abortion.