What is an early pregnancy scan?

An early pregnancy scan is any ultrasound before the routine dating scan, usually to check where the pregnancy is and whether there is a heartbeat. On the NHS it is not routine: the first scan most people have is the 12-week dating scan. The NHS week-by-week guide says that at 6 weeks the heartbeat can sometimes be picked up on a vaginal ultrasound, "but you are unlikely to be offered one unless you've had IVF".

Early scans on the NHS are offered for a reason: pain, bleeding, your history or IVF. Australia works differently: Pregnancy, Birth and Baby says the dating scan there is most often done in the first trimester, "usually between 6 and 8 weeks of pregnancy", and that Medicare covers it, though there may be out-of-pocket costs.

Who is offered an early scan on the NHS?

Early scans are done by early pregnancy assessment services, often called early pregnancy units (EPUs). NICE guideline NG126 says these should be available 7 days a week, offer ultrasound and hCG blood tests, and be able to see you within 24 hours when the situation warrants it.

NICE says EPUs should accept self-referrals from women who have had recurrent miscarriage or a previous ectopic or molar pregnancy. Everyone else with pain or bleeding should be assessed first by a GP, A&E doctor, midwife or nurse, who should refer you if you have bleeding or other symptoms and:

pain, or
a pregnancy of 6 weeks or more, or
a pregnancy of uncertain gestation.

If you are under 6 weeks, bleeding but not in pain, and have no risk factors such as a previous ectopic pregnancy, NICE recommends waiting rather than scanning: return if the bleeding continues or pain develops, and repeat a urine pregnancy test after 7 to 10 days. A positive test means you should go back; a negative one means the pregnancy has miscarried. NICE also notes that about a third of women with an ectopic pregnancy have no known risk factors, which is why it says ectopic pregnancy should be ruled out even when you have none.

What can an early scan show, and when?

Structures appear in a set order: first the gestational sac, then the yolk sac inside it, then the embryo (the fetal pole) with a flickering heartbeat. At the EPU, NICE recommends a transvaginal (vaginal) scan to find where the pregnancy is and whether there is a fetal pole and heartbeat; if you would rather not have one, it says the limitations of a scan through the tummy should be explained.

A 1989 transvaginal study of 53 women with normal pregnancies gives a sense of timing, counted from the first day of the last period:

What became visible	Days	Roughly
Gestational sac (always seen after this point)	32	4 weeks 4 days
Yolk sac (first seen in every woman within this range)	36 to 40	5 weeks 1 day to 5 weeks 5 days
Embryo with a heartbeat (every woman with accurate dates beyond this)	40	5 weeks 5 days

Treat those as findings from a small, old study of pregnancies with certain dates, not as a deadline for yours. NICE is explicit that clinicians should not use the date of your last period alone to decide whether a heartbeat should be visible, because cycle lengths vary. A late ovulation can make a normal pregnancy look "behind" on period dates. If you are tracking hCG results alongside scans, the hCG doubling time calculator shows how your results are changing.

What if the scan does not show what you expected?

Usually you will be asked to come back. NICE warns that a miscarriage diagnosed on a single scan "cannot be guaranteed to be 100% accurate", particularly at very early gestations, so it sets size thresholds before anyone can call it:

Finding on a transvaginal scan	What NICE recommends
Embryo under 7.0 mm, no heartbeat	A second scan at least 7 days later before any diagnosis
Embryo 7.0 mm or more, no heartbeat	A second opinion and/or a second scan at least 7 days later
Sac under 25.0 mm across, no embryo	A second scan at least 7 days later before any diagnosis
Sac 25.0 mm or more, no embryo	A second opinion and/or a second scan at least 7 days later

If those measurements are taken through the tummy rather than the vagina, NICE says to wait at least 14 days before the second scan. It also says you should be told that waiting for a repeat scan "has no detrimental effects on the outcome of the pregnancy", and be given a 24-hour phone number while you wait.

An empty womb with a positive test is called a pregnancy of unknown location. It can be a very early pregnancy, a miscarriage, or an ectopic pregnancy, and NICE asks for follow-up with hCG levels and scans until there is a definite answer. Bleeding in early pregnancy and what happens in a miscarriage cover the next steps.

Private early reassurance scans

A private scan uses the same equipment and is bound by the same biology. Booked too early, it may show only a sac, and the NICE thresholds above still decide what a missing heartbeat means. If a private scan finds something worrying, take the report to your GP or midwife, who can refer you to the EPU.

On safety, the Australian Government's Pregnancy, Birth and Baby service says ultrasound in pregnancy does not harm you or your baby or increase your risk of miscarriage. In the US, the Food and Drug Administration (FDA) says ultrasound is "generally considered safe when used prudently" by trained providers, notes that it can heat tissue slightly and that long-term consequences of these effects "are still unknown", and discourages scans done solely for keepsake images. Its view is that keepsake pictures are reasonable when taken during a medically needed scan with no extra exposure.

When to get help urgently

Do not wait for a booked scan if you have symptoms. The NHS says to call your maternity unit, or an early pregnancy unit if you are under 20 weeks, if you have light bleeding or spotting with no or only mild pain, unusual discharge, or fluid leaking. If you cannot reach either, call NHS 111.

Call 999, or your local emergency number, if you have vaginal bleeding and any of these:

severe pain in your tummy that stops you doing daily tasks
pain in your shoulder
you feel sick, faint or dizzy, or lose consciousness
heavy bleeding that soaks a period pad soon after you put it on

Frequently asked questions

Why did my early ultrasound show nothing when I'm pregnant?

It may simply be too early, particularly if you ovulated later than your period dates assume; NICE says period dates can mislead because cycles vary. An empty womb is called a pregnancy of unknown location and is followed up with hCG tests and scans until it is clear whether the pregnancy is early, has miscarried or is ectopic.

How early can a scan show a heartbeat?

In a 1989 study of women with certain dates, a heartbeat was seen on a vaginal scan in everyone beyond 40 days from their last period, about 5 weeks and 5 days. Your own timing depends on when you ovulated, which is why NICE says not to rely on period dates alone.

Can I refer myself to an early pregnancy unit?

In England, NICE says EPUs should accept self-referrals if you have had recurrent miscarriages or a previous ectopic or molar pregnancy. Otherwise a GP, A&E doctor, midwife or nurse assesses you first. If you have a maternity unit, the NHS says to call them; under 20 weeks, an EPU may help.

Is a vaginal scan safe in early pregnancy?

Yes. NICE recommends a transvaginal scan as the standard test at early pregnancy units, and the 1989 study found it identified a normal pregnancy a week earlier than a scan through the tummy. Pregnancy, Birth and Baby says the probe is not usually painful and that ultrasound does not increase the risk of miscarriage.

Early Pregnancy Scans