At what level of b-HcG is it that normal pregnancy can be earliest detected by TVS (Transvaginal USG) :
**Core Concept**
Normal pregnancy can be detected by transvaginal ultrasound (TVS) due to the presence of the gestational sac, yolk sac, and embryo. The earliest detection of pregnancy by TVS is possible when the beta-human chorionic gonadotropin (β-hCG) levels are sufficiently high to allow visualization of these structures.
**Why the Correct Answer is Right**
The β-hCG levels must be at least 1000-2000 mIU/mL for the gestational sac to be visible on TVS. This is because the β-hCG hormone stimulates the endometrium to thicken and prepare for implantation, and its levels increase exponentially during early pregnancy. The gestational sac is usually visible on TVS when it reaches a size of about 2-3 mm in diameter, which corresponds to a β-hCG level of around 1000-2000 mIU/mL.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Option D:** This option is not provided.
**Clinical Pearl / High-Yield Fact**
It is essential to note that β-hCG levels can vary significantly between individuals, and a level of 1000-2000 mIU/mL may not always correspond to the earliest detectable pregnancy by TVS. However, in general, this range is a useful benchmark for clinicians and sonographers to assess the likelihood of a normal pregnancy.
**Correct Answer:** 1000-2000.