16 weeks pregnant
Your baby is about 11.5 cm and 100 grams; first movements may be felt.
At week 16, your baby reaches 100 grams. Mums-to-be in their second pregnancy may start to feel the first movements around this time.
This week’s ultrasound image
Expected ultrasound appearance and measurements at week 16 (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)
Crown–rump length
115 mm
Head diameter
35 mm
Head circumference
125 mm
Femur length
21 mm
Estimated weight
100 g
Heart rate
152 bpm
How big is your baby this week?
About the size of an avocado
What can be seen on the ultrasound?
BPD is about 35 mm, HC about 125 mm, AC about 108 mm and FL about 21 mm. The heart rate is about 150 beats per minute. The baby’s sex can often be seen.
Your baby’s development
Your baby is about the size of an avocado. The eyes move slowly and the facial muscles are developing. The heart pumps about 25 litres of blood a day.
Changes in your body
You may have short, sharp pains at the sides of your lower abdomen (round ligament pain as the womb’s ligaments stretch). Your skin may look glowing or develop dark patches.
Check-ups at this stage
- Routine check and quadruple test results
- Booking your anomaly scan for weeks 18–22
- Checking your iron levels
Tips for this week
- Roll onto your side first when getting out of bed
- Gentle stretching and walking can ease ligament pain
- Start noting down when you notice your baby’s movements
When should you see your doctor?
Contact your doctor if you have bleeding, regular contractions, leaking fluid, sudden swelling of the face and hands, or blurred vision.
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
When will I feel my baby move?
In a first pregnancy, movements are usually felt at weeks 18–20; in women who have given birth before, around week 16. The first movements feel like a gentle flutter or bubbles.
Can the baby’s sex be seen at 16 weeks?
It can often be seen on ultrasound, but this depends on the baby’s position, and accuracy increases at weeks 18–20.
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