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Difficulty: HardObstetric Complications

Match each clinical vignette describing a third-trimester obstetric complication with its primary underlying pathophysiologic mechanism.

  • A 34-year-old gravida 2, para 1 at 37 weeks gestation with chronic hypertension presents with sudden-onset, severe back pain. The uterus is rigid, exquisitely tender, and contracting every 2 minutes. Vaginal bleeding is minimal.Premature detachment of the placenta leading to a retroplacental hematoma
  • A 29-year-old gravida 3, para 0 at 39 weeks gestation with a history of myomectomy presents in active labor. She suddenly reports a sharp, tearing abdominal pain followed by the cessation of uterine contractions and loss of fetal station.Full-thickness separation of the uterine musculature and serosa
  • A 26-year-old gravida 1, para 0 at 36 weeks gestation with a bilobed placenta experiences sudden-onset vaginal bleeding immediately following artificial rupture of membranes. The fetal heart rate promptly drops to 75/min with no variability.Tearing of unprotected fetal vessels crossing the internal cervical os
  • A 31-year-old gravida 4, para 3 at 35 weeks gestation presents with recurrent episodes of painless, bright red vaginal bleeding. She has a history of two prior cesarean deliveries and no other medical conditions.Implantation of the placenta directly over the internal cervical os

Answer

Vignette 1 matches with premature detachment of the placenta (abruption). Vignette 2 matches with full-thickness separation of the uterine musculature (rupture). Vignette 3 matches with tearing of unprotected fetal vessels (vasa previa). Vignette 4 matches with implantation of the placenta directly over the internal cervical os (previa).
Each clinical vignette provides classic risk factors and presenting symptoms that uniquely map to a specific pathophysiologic mechanism. Placental abruption is characterized by painful, rigid uterine findings; uterine rupture by sudden loss of contractions and fetal station in the setting of prior uterine surgery; vasa previa by post-amniotomy bleeding with fetal bradycardia; and placenta previa by painless bright red bleeding.

Step-by-Step Solution

1
Analyze the first vignette to identify the underlying etiology.
The combination of chronic hypertension, severe back pain, and a rigid, contracting uterus indicates placental abruption.
Chronic hypertension causes vascular changes that predispose to abruption, which classically presents with a hypertonic, tender uterus even if bleeding is concealed.
2
Evaluate the second vignette based on the patient's surgical history and intrapartum event.
A prior myomectomy followed by sudden cessation of contractions and loss of fetal station points to uterine rupture.
Myomectomy scars weaken the uterine wall, making it susceptible to full-thickness separation during the stress of labor, leading to loss of intrauterine pressure.
3
Assess the third vignette focusing on the timing of bleeding and fetal heart rate changes.
Bleeding and abrupt fetal bradycardia immediately after membrane rupture in a patient with a bilobed placenta indicates vasa previa.
Unprotected fetal vessels in the membranes are vulnerable to tearing during amniotomy, leading to rapid fetal exsanguination.
4
Examine the fourth vignette to diagnose the cause of bleeding.
Painless, bright red bleeding in a multiparous patient with prior cesarean deliveries suggests placenta previa.
Uterine scarring from prior surgeries alters placental implantation, increasing the risk of the placenta covering the cervical os.

Key Concept

Differentiating etiologies of third-trimester obstetric bleeding and complications based on maternal risk factors, pain character, uterine tone, and fetal heart rate patterns.
Estimated Time:1m 30s
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Topics

Obstetric Complications

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