**Core Concept**
A blighted ovum, also known as an anembryonic pregnancy, is a type of early pregnancy loss where a gestational sac forms in the uterus, but no embryo is present. This condition is often associated with chromosomal abnormalities in the embryo.

**Why the Correct Answer is Right**
In a blighted ovum, the embryo fails to implant or develop, leading to a non-viable pregnancy. The gestational sac, which is formed by the trophoblast, continues to grow, but there is no fetal pole or embryo present. This condition is often diagnosed on ultrasound between 5-10 weeks of gestation, when the absence of an embryo is evident.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the definition of a blighted ovum.
**Option B:** This option is incorrect because a blighted ovum is characterized by the absence of an embryo, not the presence of a normal embryo.
**Option C:** This option is incorrect because a blighted ovum is not associated with an ectopic pregnancy, which is a pregnancy that develops outside the uterus.

**Clinical Pearl / High-Yield Fact**
A blighted ovum is often associated with a high risk of recurrent pregnancy loss, and patients should be counseled on this risk. Additionally, the diagnosis of a blighted ovum can be challenging, and a repeat ultrasound may be necessary to confirm the absence of an embryo.

**Correct Answer: C.**