Blighted ovum (anembryonic pregnancy)

By trimester

Weeks 1–13

1st trimester

Early first trimester: an empty sac below definitive ultrasound thresholds is an uncertain finding, not final proof of loss. Confirm location, symptoms, dating uncertainty, mean sac diameter, yolk-sac status, and the exact repeat-scan interval before any irreversible step.

Weeks 14–27

2nd trimester

Later first trimester: once conservative ultrasound criteria confirm anembryonic pregnancy, review expectant, medication, and uterine-evacuation pathways, including likely bleeding, follow-up, access to urgent care, and whether tissue testing would be useful after recurrent losses.

Weeks 28–birth

3rd trimester

After the loss: follow the clinician's plan for confirming completion and seek support for grief. A prior anembryonic pregnancy does not show that the patient caused the loss. Discuss recurrent-loss evaluation based on the complete history rather than assuming one empty-sac pregnancy predicts the next.

What does the evidence show for blighted ovum?

• Anembryonic pregnancy means a gestational sac forms without a visible embryo and may be asymptomatic or accompanied by bleeding and cramping. StatPearls uses the more descriptive term in place of blighted ovum and emphasizes ultrasound confirmation rather than symptoms alone. 1
• ACOG supports conservative ultrasound criteria because older cutoffs could incorrectly classify a viable pregnancy. When findings are uncertain, patient preferences, symptoms, and the consequences of waiting should guide the timing of repeat imaging before an irreversible decision. 2
• A prospective multicenter study of pregnancies with uncertain viability found 100% specificity for loss when an empty gestational sac had a mean diameter of at least 25 mm. It also showed that repeat-scan rules depend on initial sac size and what structures were seen, so a single waiting interval does not fit every scan. 3
• NCBI's gestational-sac review distinguishes an empty sac measuring 16 to 25 mm, which is suspicious, from an empty sac measuring 25 mm or more, which meets a failure criterion. When the finding remains uncertain, serial hCG can supplement repeat imaging but should not stand alone. 4
• A 2024 retrospective study of placental villi from anembryonic pregnancies found chromosomal abnormalities in half of the sampled cases and a normal chromosome complement in half. The selected tissue samples and assay do not establish the cause of every anembryonic pregnancy or imply that parental behavior caused it. 5

When should I call my provider about blighted ovum?

Seek urgent care for severe or one-sided pelvic pain, shoulder pain, fainting, dizziness, fever, foul discharge, or bleeding that rapidly soaks pads. These findings can signal major blood loss, infection, or an ectopic pregnancy that was not excluded. An empty or uncertain uterine sac should never be used to dismiss worsening symptoms. If you are ever unsure which side of the line you are on, make the call. Obstetric teams handle these check-ins as routine, not as overreacting.