5 weeks pregnant
A small gestational sac and yolk sac can be seen inside the womb.
By week 5, the gestational sac is large enough to be seen on transvaginal ultrasound. This is when it can be confirmed that the pregnancy is inside the womb.
This week’s ultrasound image
Expected ultrasound appearance and measurements at week 5 (illustrative, to-scale drawing).
Abbreviations on the screen
- GS
- Gestational sac diameter
- YS
- Yolk sac
- CRL
- Crown–rump length
- NT
- Nuchal translucency
- BPD
- Biparietal diameter (head width)
- HC
- Head circumference
- AC
- Abdominal circumference
- FL
- Femur (thigh bone) length
- EFW
- Estimated fetal weight
- FHR
- Fetal heart rate (beats per minute)
- GA
- Gestational age (weeks + days)
- UA PI
- Umbilical artery Doppler resistance (PI)
Gestational sac
7 mm
How big is your baby this week?
About the size of a sesame seed
What can be seen on the ultrasound?
A round, black gestational sac measuring 5–8 mm can be seen inside the womb. Towards the end of the week, the yolk sac appears within it as a bright ring. The embryo usually cannot be seen yet.
Your baby’s development
The embryo is about the size of a sesame seed (1–2 mm). The neural tube, which will form the brain and spinal cord, begins to close, and the heart tube – the earliest form of the heart – takes shape.
Changes in your body
Nausea, needing to pass urine more often, fuller breasts, sensitivity to smells and marked tiredness may begin.
Check-ups at this stage
- First transvaginal ultrasound: confirming the sac is inside the womb
- Beta-hCG monitoring if needed
- Reviewing medication doses if you have a long-term condition
Tips for this week
- Eat small, frequent meals; not letting your stomach get empty helps reduce nausea
- Drink plenty of water and make time to rest
- Avoid raw meat, raw eggs and unpasteurised dairy products
When should you see your doctor?
If you have heavy bleeding, severe cramping pain or pain on one side, contact your doctor without delay.
Growth by week
Values are averages; differences of a few days or a few millimetres between babies are normal.
| Pregnancy weeks | Crown–rump length (cm) | Weight (g) |
|---|---|---|
| Week 4 | — | — |
| Week 5 | — | — |
| Week 6 | 4 mm | — |
| Week 7 | 10 mm | — |
| Week 8 | 16 mm | 1 g |
| Week 9 | 23 mm | 2 g |
| Week 10 | 32 mm | 4 g |
| Week 11 | 43 mm | 8 g |
| Week 12 | 55 mm | 14 g |
| Week 13 | 68 mm | 23 g |
| Week 14 | 85 mm | 43 g |
| Week 15 | 100 mm | 70 g |
| Week 16 | 115 mm | 100 g |
| Week 17 | 128 mm | 140 g |
| Week 18 | 140 mm | 190 g |
| Week 19 | 152 mm | 240 g |
| Week 20 | 25.6 cm | 300 g |
| Week 21 | 26.7 cm | 360 g |
| Week 22 | 27.8 cm | 430 g |
| Week 23 | 28.9 cm | 501 g |
| Week 24 | 30 cm | 600 g |
| Week 25 | 31.9 cm | 660 g |
| Week 26 | 33.8 cm | 760 g |
| Week 27 | 35.6 cm | 875 g |
| Week 28 | 37.5 cm | 1005 g |
| Week 29 | 38.8 cm | 1153 g |
| Week 30 | 40 cm | 1319 g |
| Week 31 | 41.3 cm | 1502 g |
| Week 32 | 42.5 cm | 1702 g |
| Week 33 | 43.6 cm | 1918 g |
| Week 34 | 44.8 cm | 2146 g |
| Week 35 | 45.9 cm | 2383 g |
| Week 36 | 47 cm | 2622 g |
| Week 37 | 48 cm | 2859 g |
| Week 38 | 49 cm | 3083 g |
| Week 39 | 50 cm | 3288 g |
| Week 40 | 51 cm | 3462 g |
Frequently asked questions
Can a heartbeat be seen at 5 weeks?
Usually not. In most pregnancies, the heartbeat is seen around week 6, when the embryo measures 2–4 mm.
Should I worry if the sac looks empty?
It is normal not to see an embryo inside the sac at 5 weeks. Your doctor will usually recommend a follow-up scan in 7–10 days.
Your pregnancy care at SoftCare Clinic
Book an appointment with our specialist doctors for your ultrasound check-up and any questions you may have.
The information on this page is for general guidance only and does not replace a medical examination. Measurements are average values; please discuss your own results with your doctor.
Medical content editor: Op. Dr. Şükrü Sanus