**Core Concept:** Human Chorionic Gonadotropin (hCG) is a hormone produced by the trophoblastic cells in a pregnant woman's body. Transvaginal ultrasound (TVS) is a specialized ultrasound technique that allows for earlier and more accurate detection of pregnancy compared to abdominal ultrasound (USG).

**Why the Correct Answer is Right:** The earliest detection of a normal pregnancy using TVS is at around 6-8 weeks post-conception. This is due to the increased sensitivity and resolution of the transvaginal ultrasound probe, which can penetrate deeper into the pelvis and provide clearer images of the gestational sac and yolk sac formation.

**Why Each Wrong Option is Incorrect:** Option A is incorrect because the human chorionic gonadotropin (hCG) levels increase dramatically within the first few weeks post-conception, leading to earlier detection of pregnancy using TVS. Option B is incorrect because the correct answer indicates that TVS can detect pregnancy at 6-8 weeks, not at week 10. Option C is incorrect as it does not specifically address the timing of pregnancy detection using TVS. Option D is incorrect because it does not mention the role of hCG levels in early pregnancy detection or the advantage of TVS in detecting pregnancy.

**Why the Correct Answer is Right:** By 6-8 weeks post-conception, the levels of human chorionic gonadotropin (hCG) in the bloodstream are high enough to be detected using TVS, making it the optimal time for detecting a normal pregnancy.

**Clinical Pearl:** Early detection of pregnancy is essential for appropriate obstetric management, including counseling on contraception, planning of antenatal care, and assessing for potential complications such as ectopic pregnancy or molar pregnancy. TVS is a valuable tool in this process due to its increased sensitivity and resolution.