Missed Miscarriage: Ultrasound Criteria
A 17-year-old primigravida attends for her first visit with a positive pregnancy test and a last menstrual period 9 weeks ago. She has no pain or bleeding, blood pressure 112/70 mm Hg, pulse 76 beats/min, and the cervical os is closed. Transvaginal ultrasound shows an intrauterine embryo with a crown-rump length of 24 mm and no cardiac activity. Which of the following is the most likely diagnosis?
- A.Missed miscarriageCorrect
- B.Septic miscarriage
- C.Inevitable miscarriage
- D.Threatened miscarriage
Explanation
A missed miscarriage is a non-viable intrauterine pregnancy in which the embryo has died but nothing has been expelled, so the cervix stays closed and the woman is often entirely asymptomatic. Ultrasound criteria for definite early pregnancy loss are a crown-rump length of 7 mm or more with no cardiac activity, or a mean sac diameter of 25 mm or more with no embryo; this embryo measures 24 mm, far above the threshold, so the diagnosis is certain and does not need a repeat scan. Threatened miscarriage requires vaginal bleeding through a closed os with a live fetus, and inevitable miscarriage requires cervical dilatation or ruptured membranes, neither of which is present. Septic miscarriage adds fever, offensive discharge and uterine tenderness. Management options are expectant, medical with mifepristone followed by misoprostol, or surgical uterine aspiration, chosen according to bleeding, patient preference and available follow-up. Rh-negative women should receive anti-D immunoglobulin, particularly after surgical management. Emotional support and clear explanation that the loss was not caused by anything she did are an essential part of care. Most first-trimester losses result from sporadic chromosomal abnormalities and do not require investigation after a single event.
Why each option
- A.
- Correct. A dead embryo with crown-rump length above 7 mm retained behind a closed cervix defines missed miscarriage.
- B.
- Septic miscarriage requires fever, offensive discharge and uterine tenderness, which are absent.
- C.
- Inevitable miscarriage requires an open cervical os or ruptured membranes.
- D.
- Threatened miscarriage requires vaginal bleeding with a viable pregnancy and a closed os.
Reference: ACOG Practice Bulletin No. 200, Early Pregnancy Loss, reaffirmed 2021
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