By Yianni Kiromitis — PgC Medical Ultrasound, BSc (Hons). HCPC-registered Sonographer (RA38415)

Medically reviewed by Yianni Kiromitis, HCPC-registered Sonographer (RA38415) — 15 July 2026

Last reviewed: 15 July 2026

By eight weeks, a heartbeat can usually be seen clearly on an internal scan, so not seeing one at this stage carries more weight than at six or seven weeks. Even so, it is not a diagnosis on its own. The same careful rules that apply at seven weeks still apply at eight: a single scan is never enough, and a second opinion is always sought before anything is confirmed.

This guide explains what sonographers look for at eight weeks, what the absence of a heartbeat means at this stage, and the steps that always follow before any conclusion is reached.

What a scan shows at 8 weeks

At eight weeks, the embryo typically measures between 14 and 20 millimetres from crown to rump — about the size of a raspberry. On an internal (transvaginal) scan, the heartbeat is usually clearly visible at this stage, flickering rapidly on the screen. The embryo has a recognisable shape, with a large head and small limb buds beginning to form.

Why no heartbeat at 8 weeks is more significant

At seven weeks, the absence of a heartbeat is often explained by dates being out — the pregnancy may simply be earlier than thought. By eight weeks, this explanation becomes less likely. An embryo measuring 14 millimetres or more without a heartbeat on an internal scan is a more concerning finding. However, national guidance (NICE NG126) is still clear: a single scan is never enough. A second opinion from a different clinician must be sought before any diagnosis of miscarriage is made.

The NICE NG126 criteria

The key threshold in national guidance is an embryo measuring 7 millimetres or more on an internal scan with no visible heartbeat. At this size, the absence of a heartbeat is considered significant — but the guidance still requires a second opinion before any diagnosis. This rule exists because measurements can vary between sonographers, and the consequences of a wrong diagnosis are profound.

What happens next

If no heartbeat is seen at eight weeks, the next step is usually a second scan by a different clinician, often the same day or within a day or two. This is not a delay — it is a safeguard. If both scans agree, the picture becomes much clearer. Your sonographer will explain exactly what was seen and what the next steps are.

From our practice

An eight-week scan without a heartbeat is one of the hardest conversations in our clinic. I always take time to explain the measurement and what it means — and to be honest that, even at this stage, we do not make a diagnosis alone. The second-opinion rule is not a formality; it is there because I have seen cases where a repeat scan, even a day later, has shown a heartbeat that was not visible the first time. We always follow the guidance, and we always make sure the person in front of us understands what is happening and what comes next. If you need a second opinion or a repeat scan, our early pregnancy scan service is available at short notice.

Source: NICE NG126, Ectopic pregnancy and miscarriage: diagnosis and initial management — viability assessment criteria. Verified 14 July 2026. Practice pattern: IUS London early-pregnancy imaging team.