Differential Diagnosis
- Single most likely diagnosis
- Missed abortion: This is the most likely diagnosis given the low serum β-human chorionic gonadotropin concentration for gestational age, the presence of a fluid-containing sac with a double decidual layer, and the absence of cardiac activity on transvaginal ultrasonography. The crown-rump length of 24 mm is consistent with a gestational age of around 9 weeks, but the lack of cardiac activity at this stage suggests a non-viable pregnancy.
- Other Likely diagnoses
- Gestational trophoblastic disease: Although less likely, gestational trophoblastic disease could be considered due to the low β-human chorionic gonadotropin levels and the presence of a fluid-containing sac. However, the absence of characteristic ultrasonographic findings such as a "snowstorm" appearance and the lack of significantly elevated β-human chorionic gonadotropin levels make this diagnosis less probable.
- Do Not Miss
- Ectopic pregnancy (including Interstitial pregnancy): Although the transvaginal ultrasonography shows a sac within the uterine fundus, an ectopic pregnancy, including an interstitial pregnancy, must be considered and ruled out due to its potential for severe morbidity and mortality. The presence of a closed cervical os and a uterus consistent with a 9-week gestation makes this less likely, but it cannot be entirely excluded without further evaluation.
- Rare diagnoses
- Pseudocyesis: This is a rare condition where a woman believes she is pregnant along with some physical symptoms, but there is no actual pregnancy. Given the positive pregnancy test and the ultrasonographic findings, this diagnosis is highly unlikely.
- Incomplete abortion: This would typically present with vaginal bleeding and an open cervical os, which is not consistent with the patient's presentation of a closed cervical os and no vaginal discharge.
- Threatened abortion: This diagnosis is characterized by vaginal bleeding with or without abdominal pain in the presence of a closed cervical os and a viable fetus. The absence of vaginal bleeding and the lack of cardiac activity on ultrasonography make this diagnosis unlikely.