Reproductive · Obstetrics
The facts most likely to be tested
A threatened abortion is defined as vaginal bleeding occurring before 20 weeks gestation with a closed cervical os.
The cervical os remains closed in a threatened abortion, which is the critical feature that distinguishes it from an inevitable abortion.
Transvaginal ultrasound is the diagnostic gold standard to confirm a viable intrauterine pregnancy by demonstrating fetal cardiac activity.
Patients with a threatened abortion should be advised to maintain pelvic rest and avoid strenuous activity, though bed rest has not been shown to improve outcomes.
Serum beta-hCG levels should be trended every 48 hours to confirm appropriate doubling time if the ultrasound findings are indeterminate.
Rh-negative patients presenting with vaginal bleeding must receive Rho(D) immune globulin to prevent isoimmunization.
The majority of pregnancies diagnosed with a threatened abortion will progress to a successful delivery if a fetal heartbeat is confirmed on ultrasound.
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A 28-year-old G1P0 woman at 9 weeks gestation presents to the emergency department with a small amount of bright red vaginal bleeding. She denies abdominal pain or cramping. On physical examination, the cervical os is closed and no products of conception are visualized. A transvaginal ultrasound reveals an intrauterine pregnancy with a fetal heart rate of 160 bpm.
What is the most appropriate management for this patient?
Expectant management and pelvic rest
The patient presents with the classic findings of a threatened abortion (bleeding with a closed os and viable fetus), which is managed expectantly as the pregnancy is currently viable.
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Etiology / Epidemiology
Common in first trimester pregnancies; associated with advanced maternal age and prior pregnancy loss.
Clinical Manifestations
Presents as vaginal bleeding with a closed cervical os and a viable fetus on ultrasound.
Diagnosis
Transvaginal ultrasound is the gold standard to confirm fetal cardiac activity.
Treatment
Management is expectant; avoid intercourse and heavy lifting until bleeding resolves.
Prognosis
Approximately 50% of patients will progress to a complete miscarriage.
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Epidemiology & Etiology
Occurs in up to 25% of all clinically recognized pregnancies. Primary risk factors include advanced maternal age, history of prior spontaneous abortion, and chromosomal abnormalities in the fetus. It is the most common cause of first-trimester bleeding.
Pertinent Anatomy
The cervical os remains closed, distinguishing this from inevitable or incomplete abortion. The uterus is typically size-appropriate for gestational age, and the products of conception remain entirely within the uterine cavity.
Pathophysiology
Bleeding results from partial separation of the placenta or decidua from the uterine wall. The chorionic villi remain attached to the endometrium, maintaining pregnancy viability. If the process continues, it may progress to inevitable abortion or resolve as the hematoma resorbs.
Clinical Manifestations
Patients present with vaginal bleeding and mild, crampy suprapubic pain. The cervical os is palpably closed on bimanual exam. Heavy vaginal bleeding or hemodynamic instability suggests an alternative diagnosis like ectopic pregnancy or incomplete abortion.
Diagnosis
Transvaginal ultrasound is the diagnostic test of choice to confirm fetal cardiac activity. Serial beta-hCG levels should be monitored to ensure appropriate doubling every 48 hours, confirming a viable intrauterine pregnancy.
Treatment
Management is expectant with pelvic rest. Patients are advised to avoid sexual intercourse and strenuous physical activity. If the patient is Rh-negative, administer Rho(D) immune globulin to prevent alloimmunization.
Prognosis
Prognosis is variable; roughly 50% of patients will eventually miscarry, while the remainder will have a successful pregnancy. Patients should be monitored for the development of cervical dilation or worsening pain.
Differential Diagnosis
Inevitable abortion: open cervical os
Incomplete abortion: passage of tissue with open cervical os
Ectopic pregnancy: adnexal mass and low-rising beta-hCG
Cervical insufficiency: painless cervical dilation in second trimester
Molar pregnancy: snowstorm pattern on ultrasound