What is the next step for diagnosis in a pregnant woman at 18 weeks gestation with decreased fetal movement and no fetal heartbeat on ultrasound, when the previous visit showed a normal fetus and placenta with a normal fetal heartbeat?

Next Step for Diagnosis: Ultrasound Abdomen (Option D)

The next step is to perform an ultrasound examination (USG Abdomen) to confirm fetal demise and evaluate for potential causes. 1, 2

Rationale for Ultrasound as the Diagnostic Step

• Real-time ultrasound visualization of the fetal heart is the most accurate method for diagnosing fetal death, and absence of cardiac motion definitively confirms fetal demise. 2

• At 18 weeks gestation, ultrasound can reliably document absent cardiac activity, assess fetal anatomy for structural abnormalities that may have caused the demise, evaluate placental appearance, and measure amniotic fluid volume. 1

• The Society of Radiologists in Ultrasound recommends using the term "Diagnostic of Early Pregnancy Loss (EPL)" or "fetal demise" (specifically at ≥11 weeks gestation) when cardiac activity is absent. 1, 3

Why Tissue Sampling is NOT the Next Step

• Amniocentesis (Option A), placental tissue sampling (Option B), and umbilical tissue sampling (Option C) are NOT appropriate as the immediate next diagnostic step because fetal demise must first be confirmed with ultrasound. 1, 2

• These invasive procedures may be considered AFTER confirming fetal demise to investigate the underlying cause (such as karyotyping for chromosomal abnormalities, which account for 50-60% of pregnancy losses), but they are not the initial diagnostic step. 3, 2

• Approximately 50% of fetal deaths remain "unexplained stillbirths," and special tests including karyotype, listerial culture, fetomaternal hemorrhage assessment, and lupus anticoagulant may identify causes in these cases - but only after ultrasound confirmation of demise. 2

Additional Ultrasound Findings to Document

• Look for pathognomonic signs of fetal death such as intravascular/intracardiac gas (which produces characteristic echogenic foci from maceration), absent cardiac motion on M-mode, and signs of tissue maceration. 4

• Assess for oligohydramnios, placental abnormalities, and any structural fetal anomalies that may explain the demise. 1, 2

Management After Diagnosis

• Once fetal demise is confirmed at 18 weeks, active evacuation (not expectant management) is recommended due to increased risk of intrauterine infection, coagulopathy, and maternal sepsis with prolonged retention. 3

• Dilation and evacuation (D&E) is the safest procedure for second-trimester fetal demise at this gestational age. 3