Low Viability Pregnancy

Low viability pregnancy is an early intrauterine pregnancy in which scan findings are suspicious for failure but not yet diagnostic, for example a small embryo without cardiac activity or a slow heart rate. The label matters because a repeat scan after an interval is required before any evacuation, so that a viable pregnancy is not terminated.

• Risk factors: maternal age above 35 years, previous miscarriage, bleeding, uncertain dates.
• Cardiac activity is expected from a crown rump length of 7 mm.
• Wrong dates are a frequent explanation.

Women may have bleeding or none, with early pregnancy symptoms that fade. Examination is normal with a closed os.

• Fewer pregnancy symptoms than expected.
• Bleeding is mild.
• Differential diagnosis: early normal pregnancy with wrong dates, early embryonic demise, anembryonic pregnancy, ectopic pregnancy, molar pregnancy.
• Complications: miscarriage, retained products, anxiety, wrongly terminated viable pregnancy if rushed.

The approach is repeat transvaginal ultrasound after 7 to 14 days.

• Suspicious findings: crown rump length below 7 mm with no heartbeat, mean sac diameter 16 to 24 mm with no embryo, embryo heart rate below 100 per minute at 6 to 7 weeks, sac without yolk sac after 6 weeks.
• Diagnostic findings: crown rump length 7 mm or more with no heartbeat, mean sac diameter 25 mm or more with no embryo.
• Serum hCG at 0 and 48 hours: a rise below 49 percent raises concern.
• Haemoglobin, blood group and Rhesus status.

The principle is not to evacuate the uterus until failure is confirmed on repeat scan.

• Supportive: explain uncertainty; written advice on bleeding and pain; avoid intercourse while bleeding.
• Pharmacological: folic acid 400 micrograms oral daily; paracetamol 1 g oral 6-hourly as needed (maximum 4 g in 24 hours); for bleeding with a previous miscarriage give micronised progesterone 400 mg vaginally twice daily until 12 weeks; if failure is confirmed give misoprostol 800 micrograms vaginally and repeat once after 3 hours if no tissue passed.
• Procedures: manual vacuum aspiration if failure is confirmed and the patient chooses surgery or has heavy bleeding or infection.
• Special groups: Rhesus negative women give anti-D immunoglobulin 250 IU IM within 72 hours of evacuation or heavy bleeding.
• Red flags: heavy bleeding, severe pain, fever above 38 degrees Celsius, collapse.
• Follow-up: repeat scan in 7 to 14 days; if a normal heartbeat is found, book antenatal care; if failure is confirmed, plan evacuation and give counselling.