17 of 40 weeks
Baby size this week
As lovely as a pear
Measurements are averages — every baby grows at their own pace.
Length 13 cm 5.1 in
Weight 140 g 0 lb 5 oz
Your baby this week
- Brown fat begins forming to keep your baby warm after birth
- Cartilage turns to bone
- The umbilical cord grows stronger and thicker
- Your baby practices moving joints
Your body this week
Round ligament pain
Backache
Nasal congestion
Skin changes
This week's to-do
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How we measure week 17
Pregnancy weeks are counted from the first day of your last menstrual period, following standard ACOG and NHS guidance. Sizes are crown-rump length in early weeks and head-to-heel from around week 20. Your care team may adjust dates after an ultrasound.
BumpCount offers general information and does not replace advice from your doctor or midwife.