Ultrasound Abdomen is the Next Diagnostic Step
In an 18-week pregnant woman presenting with decreased fetal movement and absent fetal heartbeat (previously normal), the immediate next step is ultrasound examination (USG Abdomen) to confirm fetal demise and evaluate for potential causes. 1
Diagnostic Rationale
Ultrasound serves as the definitive diagnostic modality because at 18 weeks gestation, it can reliably:
- Document absent cardiac activity to confirm fetal demise 1
- Assess fetal anatomy for structural abnormalities that may have caused the demise 1
- Evaluate placental appearance and amniotic fluid volume 1
- Measure crown-rump length (which at >15 mm without cardiac activity confirms demise) 1
The American College of Radiology specifically recommends that at 18 weeks gestation, ultrasound can reliably document all these parameters necessary for diagnosis 1.
Why Invasive Procedures Are NOT the Next Step
Amniocentesis, placental tissue sampling, and umbilical cord sampling should only be considered AFTER fetal demise is confirmed by ultrasound and only if there is a specific clinical indication to determine the cause of death 1. The American College of Obstetricians and Gynecologists emphasizes that invasive procedures follow—not precede—ultrasound confirmation of demise 1.
When to Consider Invasive Testing (After Ultrasound Confirmation)
The Society for Maternal-Fetal Medicine recommends offering diagnostic testing including chromosomal microarray analysis when:
- Fetal malformations are detected on ultrasound 2
- Fetal growth restriction was present 2
- There is unexplained isolated fetal demise at <32 weeks 2
These determinations can only be made after comprehensive ultrasound evaluation 1.
Comprehensive Ultrasound Evaluation Should Include
Beyond confirming absent cardiac activity, the ultrasound should assess:
- Signs of hydrops fetalis (fluid accumulation) 1
- Evidence of growth restriction 1
- Structural anomalies that may explain the demise 1
- Placental abnormalities 1
- Amniotic fluid volume (oligohydramnios or polyhydramnios) 2
Clinical Context and Management
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 1. This makes prompt ultrasound diagnosis critical for timely management.
Common Pitfall to Avoid
Do not proceed directly to invasive testing without ultrasound confirmation. The clinical presentation (decreased fetal movement, absent heartbeat on examination) requires objective confirmation via ultrasound before any invasive diagnostic procedures are considered 1. Ultrasound is non-invasive, immediately available, and provides comprehensive information that guides all subsequent management decisions 3.
Answer: D. USG Abdomen