USMLE® Step 1 style questions USMLE
A 30-year-old woman, gravida 1 para 0, comes to the labor and delivery triage at 24 weeks gestation due to severe abdominal pain, vaginal bleeding, and contractions. Pregnancy has been uneventful other than hypertension of 149/90 during her last visit. She has been compliant with prenatal care and took prenatal vitamins throughout the pregnancy. Medical history is significant for smoking 1 pack per day for 10 years which she reduced during pregnancy to half a pack per day. She is otherwise healthy and does not use alcohol or illicit drugs. Temperature is 37.0°C (98.6°F), pulse is 120/min, and blood pressure is 80/60 mmHg. On physical examination, the patient appears in acute distress due to pain. Pelvic examination shows a rigid and tender uterus. High-frequency and low-amplitude uterine contractions are noted. There is minimal bleeding present in the vaginal vault. There is no change in fetal station. The fetal heart rate is 160 bpm. Which of the following is the most likely diagnosis?
Placental abruption exam links
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Tanner Marshall, MS
Placental abruption is the premature separation of all or even just a part of the placenta from the uterine wall, resulting in hemorrhage, or bleeding.
This usually happens after about 20 weeks of gestation, and affects about 1% of pregnancies worldwide.
The placenta forms where the embryo attaches to the uterine wall and it’s a unique organ because it develops from both the mom and the fetus, and it’s job is to permit gas and nutrient exchange between them.
The word “placenta” literally means “flat cake.” So picture it as a cake with two layers, the maternal layer and a fetal layer.
The maternal layer, the decidua basalis, is literally a flattened out bag of blood with uterine arteries delivering blood in and uterine veins pulling blood out.
But unlike other parts of the circulatory system where blood stays within narrow blood vessels, the decidua basalis is a huge pool of blood.
The fetal layer of the placenta on the other hand is called the chorion, which is a tissue that has fingerlike projections called chorionic villi which contain tiny fetal arterioles and venules.
These villi push into the decidua basilis, like tiny fingers reaching into a warm pool of oxygen-rich maternal blood.
Gases and nutrients move back and forth between the decidua basalis and the fetal veins, by diffusing through the tissue layer of the thin chorionic villi.
Placental abruption happens when there is a separation of the uterine wall and decidua basalis.
This separation is usually caused by degeneration of the uterine arteries that supply blood to the placenta typically from chronic problems like smoking or hypertension.
These diseased vessels rupture, causing hemorrhage and separation of the placenta.
If the separation is near the margin of the placenta, it can cause vaginal bleeding, but if the separation is more central, there might be a pocket of blood that stays concealed between the decidua basalis and the uterine wall.
Placental abruption can be classified as partial or complete, depending on the degree of separation from the uterine wall.
As well as apparent or concealed, depending on whether vaginal bleeding is seen or not.
Risk factors for placental abruption include acute events like blunt trauma from a car crash, fall, or domestic violence.
Placental abruption is a third-trimester obstetrical complication whereby the placenta prematurely detaches from the uterine wall leading to heavy bleeding and decreasing the amount of oxygen and nutrients that reach the fetus. Risk factors include cocaine abuse, trauma, smoking, hypertension, and preeclampsia.
Symptoms include vaginal bleeding, abdominal pain, and back pain, and if not treated promptly, it can lead to preterm labor, fetal distress, and even death. Management is with emergency cesarean delivery if there is fetal or maternal jeopardy. In-hospital observation may be opted for if the mother and fetus are stable and not term.