How early can an ultrasound see a pregnancy?

First, how the weeks are counted

Pregnancy weeks are counted from the first day of your last period, not from the day you conceived. Conception usually happens about two weeks after that period starts, so when you’re “6 weeks pregnant,” the pregnancy itself is about 4 weeks old (Mayo Clinic, MedlinePlus).

That’s why a test and a scan so often disagree at first. Most home tests work from the first day of a missed period, which is about 4 weeks. Even then, the FDA says 10 to 20 of every 100 pregnant women will still get a negative on that day, and that testing 1 to 2 weeks after a missed period gives the most reliable result (FDA). A test looks for a hormone. A scan needs something big enough to see. The hormone comes first. Home pregnancy test or ultrasound explains what each one can tell you.

Dates from your period are also an estimate. If you ovulated later than usual, or your cycles are long, your pregnancy may be a few days to a week younger than the calendar says. It’s a common reason an early scan shows less than people expect. Our week planner turns a due date into weeks if you’d like to check yours, and How far along am I? explains why your test, app and scan can disagree.

What an ultrasound shows, week by week

These are typical weeks on an internal scan, counted from your last period. Every pregnancy keeps its own schedule, so treat them as a guide rather than a deadline (AAFP, Society of Radiologists in Ultrasound, Radiopaedia).

1. About 4 weeks: usually nothing yet. Your test may be positive, but the pregnancy is too small to show. The lining of the uterus may look thick, and that’s all.
2. About 5 weeks: the gestational sac. A small, dark, round space inside the uterus, sometimes visible a few days earlier. It’s the first sign of the pregnancy on a screen.
3. About 5½ weeks: the yolk sac. A tiny bright ring inside the sac. It feeds the embryo in the earliest weeks, and it’s the first thing a sonographer looks for inside the sac.
4. About 6 weeks: the embryo, and often the heartbeat. A small thickening beside the yolk sac, only a millimeter or two long at first, sometimes called the fetal pole. The flicker of the heartbeat usually shows from about 6 to 6½ weeks.
5. About 7 to 8 weeks: a clearer picture. The embryo grows fast: about 1 centimeter at 7 weeks (NHS) and about 1.6 centimeters at 8 (NHS). The heartbeat is easier to pick out, and the shape starts to look like a very small gummy bear.
6. About 8 to 9 weeks: head and body. On the screen, the head looks separate from the body, and tiny limb buds appear.
7. About 9 to 10 weeks: the first visible movements. About 2.2 centimeters at 9 weeks and 3 centimeters at 10 (NHS). You may see your baby wriggle on the screen, long before you can feel it.

Sizes vary from one baby to the next and from one chart to another. A large international study found that, at exactly 9 weeks, nearly all healthy babies (94 in 100) measured between about 14 and 29 millimeters (INTERGROWTH-21st). Only your doctor or midwife can say what a particular measurement means. If a scan says you’re measuring small, Measuring behind on your first ultrasound explains what it can mean and what happens next.

Reading your first picture

An early scan picture is a slice, not a photo, and it helps to know the code. Fluid shows up black, so the sac is a dark circle or oval. Tissue shows up in shades of gray and white, so the yolk sac is a bright little ring and the embryo is a small gray shape at the edge of the sac. The heartbeat’s flicker shows only on the live screen, not on a print. The letters and numbers around the edge are the machine’s settings and any measurements taken. At a medical scan, those measurements help set your due date. At a keepsake scan they don’t, and you shouldn’t read them as a result.

Internal scan or belly scan?

Early pregnancy ultrasounds come in two kinds, and the difference matters most in the first few weeks.

The one-week gap comes from the guidance doctors use. A belly scan shows the early landmarks “about one week after they are visible transvaginally,” in the words of a review for family physicians (AAFP). The StatPearls medical reference gives the sac at about 5 weeks on an internal scan and about 6 on a belly scan (StatPearls).

Is an internal scan safe this early? NHS hospital guidance says there is no increased risk of miscarriage (Leeds Teaching Hospitals NHS Trust). ACOG says ultrasound is not associated with risk to a pregnancy, but should be used only to answer a medical question or bring a medical benefit (ACOG Committee Opinion 723). The FDA and the American Institute of Ultrasound in Medicine also discourage scans done only for keepsakes (FDA, AIUM). Safety, in plain words has their statements. Is an early ultrasound safe for the baby? goes through the evidence.

Why it’s so often “too early to see”

A positive test and an empty-looking screen is one of the most common early-pregnancy scares. It can simply mean it’s early. Common reasons:

• Your dates are a few days off. Late ovulation shifts everything by days, and at 5 or 6 weeks a few days is a lot.
• It’s a belly scan. Expect each landmark about a week later than on an internal scan.
• The pregnancy is simply small. At 5 weeks the sac can be only a few millimeters across.

Sometimes an empty-looking screen is a sign of a problem, such as a pregnancy outside the uterus or an early loss, and these can start without symptoms. That’s why your doctor or midwife should know, even if you feel well.

Doctors are careful here, and for good reason. Under the consensus criteria radiologists use for early scans, one uncertain scan rarely settles anything. When the findings are suspicious for a loss, a follow-up scan 7 to 10 days later is “generally appropriate” (Doubilet and colleagues, New England Journal of Medicine, 2013). The Society of Radiologists in Ultrasound confirmed in 2024 that those criteria still stand. Those rules are for medical scans read by doctors. If any scan can’t show the pregnancy in the uterus, tell your doctor or midwife, even if you feel well. They may check your hormone levels with blood tests.

If seeing the heartbeat is what matters most to you, When can you see the heartbeat on an ultrasound? explains the timing in detail. If a scan doesn’t show one yet, No heartbeat on an early ultrasound covers what it can mean and what happens next.

What an early scan can tell you, and what it can’t

An early ultrasound ordered by your doctor or midwife and an elective scan like ours do different jobs. The medical one is about your health. The elective one is about seeing it.

The list on the left comes from the practice guideline for obstetric ultrasound written jointly by radiology, obstetric and ultrasound societies, including ACOG (ACR–ACOG–AIUM–SMFM–SRU). What an elective scan does is simpler, and for many families it’s the point: it shows you the pregnancy on a big screen once there’s something to see, with the people you choose, and you take pictures home.

How to pick the right week for your first look

If you want to see it for yourself, timing is most of it. As a rough guide, counted from your last period:

• To see that there’s a pregnancy on the screen: from about 5 weeks on an internal scan, and about 6 on a belly scan.
• To see the heartbeat flicker: from about 6 to 6½ weeks on an internal scan, and about a week later on a belly scan.
• To see a baby shape: from about 8 to 10 weeks, when the head, limb buds and first movements show.

If your cycles are irregular, or you’re not sure when your last period started, add a few days of margin. Or call us, tell us what you know, and we’ll help you pick a day.

Put in your due date, or your best guess, and the planner shows which of our sessions is ready now and what opens next. What you type stays on your device.

Seeing it at our studio

Our Pregnancy Check is a short, private 2D ultrasound in the first 10 weeks, at our studio in Glendale. You lie back, the big screen comes on, and we point out what you’re looking at, so the picture makes sense. You go home with 8 black-and-white prints. It’s $100, with no referral and no insurance forms.

We ask everyone to call (818) 243-7010 first, because the right week depends on your dates. Tell us the first day of your last period and we’ll tell you whether it’s a good day to come. If it’s still too early to see, you come back for a second look, almost always at no charge. Same-day appointments are often available.

Irina, our lead sonographer, has done more than 30,000 pregnancy ultrasounds over nearly two decades, and we’ve been in Glendale since 2006. What she can’t do is check on your health or date your pregnancy. That’s your doctor or midwife’s job. See how the Pregnancy Check works, or start here if your test just turned positive.

After the first look

• Book your first prenatal appointment. Many practices see you at about 8 to 10 weeks. Here’s why it isn’t sooner, and what to do until then.
• Weighing up an early scan? Is an early reassurance scan worth it? goes through who it helps and when it doesn’t.
• Wondering about referrals and cost? Can you get a pregnancy ultrasound without a doctor’s referral? compares an elective scan with a medical one, and How much does an early pregnancy ultrasound cost without insurance? has the prices.
• Curious what the scan itself is like? What to expect at your first pregnancy ultrasound walks through it, from the gel to the pictures.
• Later on: heartbeat-only visits from 11 weeks, boy or girl from 13 weeks, and 4D from 16 weeks.

Questions