Early Pregnancy Ultrasound: What to Expect at 6-8 Weeks

The first ultrasound during early pregnancy is nerve-wracking and exciting in equal measure. You're desperate to see that flicker of a heartbeat and confirm everything is developing normally. This guide walks you through what happens at ultrasounds from 6-8 weeks, week by week.

When Is the First Ultrasound?

For most low-risk pregnancies, your first ultrasound happens around 8-10 weeks. But you might have an earlier scan at 6-7 weeks if:

• You conceived through IVF or fertility treatment
• You have a history of miscarriage or ectopic pregnancy
• You're experiencing bleeding or cramping
• You have irregular periods and aren't sure of your dates
• You had concerning hCG levels that need follow-up

Earlier isn't always better. Scanning too early (before 6 weeks) might not show a heartbeat yet even in a healthy pregnancy, which creates unnecessary anxiety.

Transvaginal vs Abdominal Ultrasound

Most early ultrasounds are done transvaginally, not over your belly. Here's why:

Transvaginal Ultrasound

A wand-shaped probe is inserted into your vagina to get closer to your uterus. This provides much clearer images in early pregnancy when the embryo is still tiny. The probe is only about the size of a tampon and shouldn't hurt, though it might feel a bit uncomfortable.

You'll empty your bladder before this type of scan (unlike abdominal ultrasounds that require a full bladder).

Abdominal Ultrasound

The traditional ultrasound over your belly doesn't provide clear enough images until around 10-12 weeks. Your doctor might try an abdominal scan first, then switch to transvaginal if they can't see enough detail.

What You'll See at 6 Weeks

At 6 weeks from your last menstrual period (which is about 4 weeks after conception), here's what the ultrasound typically shows:

Gestational Sac

This appears as a dark circle inside your uterus. The sac should measure 10-15mm at this point. Your doctor will confirm the pregnancy is in your uterus (not ectopic) and measure the sac.

Yolk Sac

Inside the gestational sac, you should see a smaller circle - the yolk sac. This provides nutrients to the embryo before the placenta takes over. The yolk sac typically appears around 5.5-6 weeks and measures 3-5mm.

Fetal Pole

This is the early embryo, though it doesn't look like a baby yet - more like a tiny curved line next to the yolk sac. The fetal pole is usually visible at 6 weeks but might not be seen until 6.5 weeks in some healthy pregnancies.

Heartbeat

The heartbeat might be detectable at 6 weeks, but it's not guaranteed. The heart starts beating around 5.5-6 weeks, and ultrasound can detect it once the fetal pole measures 5mm or more. If your scan is exactly at 6 weeks 0 days, the heartbeat might not be visible yet.

Don't panic if there's no heartbeat at 6 weeks. Your doctor will schedule a follow-up scan in 7-10 days.

What You'll See at 7 Weeks

By 7 weeks, the ultrasound picture becomes clearer and more reassuring:

Heartbeat

You should definitely see a flickering heartbeat at 7 weeks. The heart rate will be 100-120 beats per minute at this stage - slower than later in pregnancy, but normal for now. Seeing the heartbeat dramatically reduces miscarriage risk (to about 5% or less).

Crown-Rump Length (CRL)

Your doctor will measure the embryo from head to bottom (crown to rump). At 7 weeks, the CRL is typically 10mm. This measurement confirms your due date more accurately than your last period date.

Embryo Shape

The embryo starts to look less like a blob and more like a tiny curved shape. You might be able to make out the head and body, though it still doesn't look like a baby.

What You'll See at 8 Weeks

The 8-week ultrasound provides the most detail and reassurance:

Clear Heartbeat

The heartbeat is strong and obvious, with a rate of 140-170 beats per minute. You can usually hear it on the ultrasound machine speaker, which makes the experience more emotional.

Embryo Movement

You might see the embryo moving or twitching, though you can't feel it yet. This spontaneous movement is a great sign of development.

Detailed Anatomy

At 8 weeks, you can start to see:

• Head and body distinction
• Limb buds (arms and legs developing)
• Facial features beginning to form

Crown-Rump Length

The embryo measures about 16mm (about the size of a raspberry). CRL measurements at 8 weeks are very accurate for dating - within 3-5 days.

Key Measurements Your Doctor Takes

Normal Heart Rates by Week

The heart rate increases during early pregnancy:

A heart rate below 100 bpm or above 180 bpm might indicate a problem and requires follow-up. But remember that heart rates at the lower end of normal at 6 weeks often increase normally by 7 weeks.

What If Something Doesn't Look Right?

Empty Gestational Sac

If the gestational sac measures 25mm or more without a visible yolk sac or embryo, this indicates a blighted ovum (anembryonic pregnancy). However, if the sac is smaller, you might just be earlier than you thought. A follow-up scan in 7-10 days will clarify.

No Heartbeat Detected

If the embryo (fetal pole) measures 7mm or more without a heartbeat, this typically indicates pregnancy loss. But if it's smaller than 7mm, the pregnancy might be less developed than expected. Your doctor will rescan in a week.

Slow Heart Rate

Heart rates below 100 bpm have a higher risk of miscarriage, but not all slow heartbeats lead to loss. If the heart rate is 80-90 bpm at 6 weeks, it might increase to normal by 7 weeks. Close monitoring is needed.

Measuring Behind

If measurements are smaller than expected for your dates, you might have ovulated later than you thought, or the pregnancy might not be developing normally. A repeat scan in 7-10 days shows whether the embryo is growing at the right pace (about 1mm per day).

What Happens During the Scan

Here's what to expect during your appointment:

1. Preparation: You'll undress from the waist down and lie on the exam table with your knees bent (for transvaginal) or with a full bladder (for abdominal).
2. Probe insertion: For transvaginal ultrasound, the sonographer covers the probe with a condom and lubricant, then gently inserts it.
3. Image capture: The sonographer moves the probe to different angles to get clear views of your uterus and embryo. You'll see the screen and can watch along.
4. Measurements: They'll freeze the image to take measurements of the gestational sac, yolk sac, embryo, and heart rate.
5. Photos: You'll usually get printout images to take home.
6. Discussion: The sonographer or your doctor will explain what they see and give you an estimated due date based on measurements.

The whole process takes 10-20 minutes. You might feel some pressure or cramping when the probe moves, but it shouldn't be painful.

Questions to Ask at Your Ultrasound

• What is the gestational age based on measurements?
• What is the crown-rump length?
• What is the heart rate?
• Is everything measuring on track for the dates?
• Is the pregnancy in the right location (uterus)?
• When is my estimated due date?
• When should I schedule my next ultrasound?

After Your Ultrasound

Once you've seen a heartbeat at 7-8 weeks, your risk of miscarriage drops significantly:

• Heartbeat at 6 weeks: About 10% miscarriage risk
• Heartbeat at 7 weeks: About 5% miscarriage risk
• Heartbeat at 8 weeks: About 2-3% miscarriage risk

Your next ultrasound will typically be the anatomy scan at 18-22 weeks, though you might have an earlier scan at 11-14 weeks for nuchal translucency screening.

Using Dating Ultrasounds to Calculate Your Due Date

The crown-rump length at 7-8 weeks is the most accurate way to date a pregnancy. Your doctor will use the CRL measurement to calculate your due date, which might be different from the date based on your last period.

Our Gestational Age Calculator lets you input ultrasound measurements (CRL) to see your estimated due date and how far along you are.

The Bottom Line

Your first ultrasound between 6-8 weeks confirms the pregnancy is in the right place and developing normally. By 8 weeks, you should see a clear heartbeat, an embryo measuring about 16mm, and maybe even some movement. These early scans provide critical information about viability and due date accuracy.

If your scan is at 6 weeks and doesn't show a heartbeat yet, don't panic. A follow-up scan at 7 weeks will likely show much more development. Trust your doctor's guidance on timing and what the measurements mean.

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