**Question:** Commonest cause of ectopic pregnancy: March 2007

**Core Concept:** Ectopic pregnancy is a life-threatening obstetric emergency where the fertilized ovum implants outside the uterine endometrial cavity. The most common site is the fallopian tube, accounting for 95% of ectopic pregnancies.

**Why the Correct Answer is Right:** The correct answer is D - tubal pregnancy, as tubal pregnancies account for the majority (95%) of all ectopic pregnancies. The fallopian tube is the most common site for ectopic implantation due to its anatomy and the presence of a functional spiral artery that can support the growing fetus.

**Why Each Wrong Option is Incorrect:**

A. Ovarian pregnancy: This is a very rare type of ectopic pregnancy where the fertilized ovum implants in the ovary. It usually occurs due to a ruptured ectopic pregnancy in the fallopian tube, leading to a secondary ovarian ectopic pregnancy.

B. Cervical pregnancy: This is another rare type of ectopic pregnancy, where the fertilized ovum implants in the cervix. Cervical pregnancy is usually associated with a previous cesarean section scar, causing the fertilized ovum to implant in the scar tissue instead of the uterine fundus.

C. Intrauterine pregnancy: This option is incorrect because an intrauterine pregnancy occurs when the fertilized ovum implants within the uterine cavity.

D. Tubal pregnancy: As mentioned, tubal pregnancies account for the majority of ectopic pregnancies due to the anatomy of the fallopian tube and the functional spiral artery.

**Clinical Pearl:**

Understanding the different types of ectopic pregnancies is crucial for early diagnosis and appropriate management, as these pregnancies can rapidly progress to life-threatening hemorrhage. Immediate intervention is necessary to prevent maternal mortality and morbidity.

**Correct Answer:** D - Tubal pregnancy