A pregnant lady in her first trimester presents with vaginal bleeding. On examination the os is closed and uterine size corresponds to the period of amenorrhoea. The condition could be: September 2005
**Core Concept**
The condition described is a common cause of vaginal bleeding in early pregnancy, characterized by implantation of the fertilized ovum in the uterine lining, leading to bleeding due to the disruption of the endometrial blood vessels.
**Why the Correct Answer is Right**
The condition is likely **Implantation Bleeding**, which occurs when the fertilized ovum implants in the uterine lining, causing minor bleeding. The closed os and uterine size corresponding to the period of amenorrhoea support this diagnosis. Implantation bleeding is thought to be caused by the release of prostaglandins and other substances that stimulate uterine contractions and bleeding.
**Why Each Wrong Option is Incorrect**
* **Option A:** Threatened abortion is incorrect because it typically occurs when there is vaginal bleeding with an open os, indicating cervical dilation and impending abortion.
* **Option B:** Inevitable abortion is incorrect because it occurs when there is vaginal bleeding with a dilated os, indicating cervical dilation and imminent abortion.
* **Option D:** Missed abortion is incorrect because it occurs when there is a non-viable intrauterine pregnancy with a closed os, but the uterine size is larger than expected for the period of amenorrhoea.
**Clinical Pearl / High-Yield Fact**
Implantation bleeding is a common cause of vaginal bleeding in early pregnancy and is usually self-limiting, requiring no treatment.
**Correct Answer:** A. Implantation bleeding.