A primigravida at 22 weeks of gestation presents to you with profuse vaginal bleeding. Her blood pressure and glucose levels are within normal limits. Placental implantation at which of the following sites can cause this?

Correct Answer: C. Internal OS

Placenta previa—implantation over the internal cervical os—is the classic cause of painless, profuse vaginal bleeding in the second and third trimesters. At 22 weeks, the patient presents with hemorrhage without pain, normal BP (suggesting acute rather than massive hemorrhage), and normal glucose—all consistent with previa rather than placental abruption or other complications. The internal os is the anatomical boundary between the lower uterine segment and cervical canal; when trophoblastic tissue implants here, the friable placental bed erodes into maternal blood vessels as the cervix effaces and dilates during pregnancy, causing recurrent bleeding episodes. This is the most common cause of antepartum hemorrhage in the second and third trimesters in Indian obstetric practice. Placenta previa occurs in ~0.5–1% of pregnancies and is diagnosed by transvaginal ultrasound (gold standard). The normal BP and glucose exclude massive hemorrhage or metabolic derangement, making previa the most likely diagnosis. Ectopic implantation sites (abdominal, tubal, ovarian) typically present with rupture, hemodynamic instability, and acute pain—not chronic bleeding at 22 weeks.

Why the other options are wrong

A. Abdominal — Abdominal (primary peritoneal) pregnancy is extremely rare and typically ruptures in the first trimester with acute hemorrhage, severe pain, and shock. A viable pregnancy reaching 22 weeks with stable vitals and profuse but non-catastrophic bleeding is inconsistent with abdominal implantation. This is a distractor based on ectopic site knowledge. B. Fallopian tube — Tubal ectopic pregnancy ruptures typically in the first trimester (8–12 weeks) with acute pain, hemodynamic collapse, and massive hemorrhage. Reaching 22 weeks with stable BP and glucose is virtually impossible with tubal implantation. NBE includes this to test whether students confuse ectopic bleeding (acute, painful) with previa bleeding (chronic, painless). D. Ovarian — Ovarian pregnancy is the rarest form of ectopic implantation and ruptures acutely in the first trimester with severe pain and hemorrhagic shock. The clinical picture of stable vitals, normal glucose, and profuse vaginal bleeding at 22 weeks excludes ovarian implantation entirely. This is a distractor testing knowledge of ectopic sites.

High-Yield Facts

Mnemonics

PREVIA vs ABRUPTION (Bleeding Pattern) Painless, Profuse, Placenta previa | Acute pain, Abruption, Acute shock. Previa = vaginal bleeding; abruption = concealed + revealed bleeding + pain. ECTOPIC RUPTURE TIMING Tubal ruptures 8–12 weeks (1st trimester); abdominal/ovarian rupture even earlier. If patient reaches 22 weeks with stable vitals → NOT ectopic.

NBE Trap

NBE pairs ectopic implantation sites (tubal, abdominal, ovarian) with antepartum hemorrhage to trap students who conflate "ectopic pregnancy" with "abnormal bleeding." The key discriminator is timing and hemodynamic stability: ectopic rupture is acute and catastrophic in the 1st trimester, whereas previa causes chronic, painless bleeding in the 2nd–3rd trimester.

Clinical Pearl

In Indian antenatal clinics, placenta previa is screened routinely by transvaginal ultrasound at 18–20 weeks; a primigravida with painless bleeding at 22 weeks and stable vitals should raise immediate suspicion for previa, and digital cervical examination must be avoided until previa is excluded by imaging. This prevents catastrophic hemorrhage from cervical manipulation.

_Reference: DC Dutta's Textbook of Obstetrics, 8th edn, Ch. 12 (Antepartum Hemorrhage); Harrison's Principles of Internal Medicine, Ch. 427 (Pregnancy Complications)_