Reproductive · Obstetrics
The facts most likely to be tested
A threatened abortion presents with vaginal bleeding and a closed cervical os with a viable intrauterine pregnancy on ultrasound.
An inevitable abortion is characterized by vaginal bleeding and cramping with a dilated cervical os but no passage of products of conception.
An incomplete abortion involves the partial passage of products of conception with a dilated cervical os and retained tissue on ultrasound.
A complete abortion is defined by the passage of all products of conception with a closed cervical os and an empty uterus on ultrasound.
A missed abortion is the fetal demise of a pregnancy without the passage of tissue and with a closed cervical os.
The most common karyotypic abnormality associated with first-trimester spontaneous abortion is autosomal trisomy.
Septic abortion is a medical emergency characterized by fever, uterine tenderness, and foul-smelling discharge requiring broad-spectrum antibiotics and uterine evacuation.
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A 28-year-old G2P1 woman at 10 weeks gestation presents to the emergency department with vaginal bleeding and lower abdominal cramping. On physical examination, the cervical os is dilated, and products of conception are visualized at the external os. Transvaginal ultrasound confirms retained tissue within the uterine cavity. The patient is hemodynamically stable and afebrile.
What is the most appropriate diagnosis?
Incomplete abortion
The presence of a dilated cervix with retained products of conception after the partial passage of tissue confirms an incomplete abortion, as defined in the second bet.
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High yield triage
Etiology / Epidemiology
Occurs in <20 weeks gestation. Chromosomal abnormalities (aneuploidy) are the most common cause.
Clinical Manifestations
Presents with vaginal bleeding and cramping. Cervical os status is the primary differentiator.
Diagnosis
Transvaginal ultrasound is the gold standard. Mean sac diameter >25 mm without an embryo confirms loss.
Treatment
Expectant management, misoprostol, or suction curettage. Infection is a contraindication to expectant management.
Prognosis
Most patients recover fully. Rh-negative mothers require Rho(D) immune globulin to prevent isoimmunization.
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Epidemiology & Etiology
Spontaneous abortion occurs in 15-20% of clinically recognized pregnancies. Advanced maternal age and prior history are the most significant clinical risk factors. The majority of first-trimester losses are due to fetal aneuploidy.
Pertinent Anatomy
The cervical os is the critical anatomical landmark for classification. Internal os dilation indicates an inevitable or incomplete process, whereas a closed os suggests threatened abortion.
Pathophysiology
The process begins with fetal demise or placental detachment, leading to uterine contractions and cervical dilation. If the products of conception are partially expelled, the uterus cannot contract effectively, leading to hemorrhage. Persistent bleeding in the setting of an open os indicates retained tissue.
Clinical Manifestations
Patients present with vaginal bleeding and suprapubic cramping. Hemodynamic instability or fever/foul-smelling discharge suggests septic abortion, a medical emergency. The cervical os status is the key physical exam finding: closed in threatened, open in inevitable/incomplete.
Diagnosis
Transvaginal ultrasound is the diagnostic gold standard. Diagnostic criteria for pregnancy failure include mean sac diameter >25 mm without an embryo or crown-rump length >7 mm without cardiac activity.
Treatment
Management depends on stability and type: expectant management, medical evacuation with misoprostol, or surgical suction curettage. Infection or hemodynamic instability mandates immediate surgical evacuation. Rho(D) immune globulin must be administered to all Rh-negative patients.
Prognosis
Most patients have an excellent prognosis for future fertility. Retained products of conception can lead to chronic bleeding or infection, requiring repeat intervention. Monitor for Rh isoimmunization in subsequent pregnancies.
Differential Diagnosis
Ectopic pregnancy: positive pregnancy test with empty uterus on ultrasound
Molar pregnancy: snowstorm appearance on ultrasound with elevated hCG
Cervical insufficiency: painless cervical dilation in the second trimester
Subchorionic hematoma: crescent-shaped fluid collection between the chorion and uterus
Implantation bleeding: light spotting occurring at the time of expected menses