Earliest diagnosis of pregnancy can be established safely by:(AIIMS May 2015, November 2013)
**Core Concept**
Human chorionic gonadotropin (hCG) is a hormone produced by the placenta shortly after implantation, serving as a marker for early pregnancy. Its detection via sensitive assays enables the earliest diagnosis of pregnancy.
**Why the Correct Answer is Right**
The earliest diagnosis of pregnancy can be safely established by detecting the presence of hCG in urine or serum. This hormone triggers a cascade of downstream effects, including the stimulation of the corpus luteum to maintain progesterone production, thereby supporting the early stages of embryonic development. The sensitivity of modern hCG assays allows for detection as early as 6-8 days post-ovulation, making it a reliable marker for early pregnancy.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the earliest diagnosis of pregnancy. The timing of the first ultrasound scan is typically around 6-8 weeks, which is later than the earliest detection of hCG.
**Option B:** While a blood test for hCG can be performed, it is not the earliest method of diagnosis. The earliest diagnosis of pregnancy is typically established via urine pregnancy tests (UPTs), which are more convenient and can be performed earlier.
**Option C:** This option is incorrect as it refers to the first ultrasound scan, which is typically performed later in pregnancy (around 6-8 weeks) to confirm fetal viability and dating.
**Clinical Pearl / High-Yield Fact**
Urine pregnancy tests (UPTs) can detect hCG as early as 6-8 days post-ovulation, making them a reliable and convenient method for early pregnancy diagnosis.
**Correct Answer: B. HCG detection via urine or serum.**