Baby Size Chart: Week by Week
Watch your baby grow from a tiny poppy seed to a full-term baby! This visual guide compares your baby's size to familiar fruits and vegetables throughout all 40 weeks of pregnancy.
Note: These measurements are averages. Every baby grows at their own pace, and your healthcare provider will monitor your baby's individual growth.
Week 1
Starting size: Poppy seed
Less than 0.1 inches
Week 20
Halfway: Banana
About 10 inches long
Week 40
Full term: Small pumpkin
About 20 inches, 7.6 pounds
Complete Size Comparison
Growth by Trimester
First Trimester (Weeks 1-13)
Rapid cellular development begins. Your baby grows from a microscopic cell to about 3 inches long. Major organs form during this critical period.
Second Trimester (Weeks 14-27)
Your baby experiences significant growth spurts. From about 3.5 inches to nearly 14 inches. Facial features develop and movements become noticeable.
Third Trimester (Weeks 28-40)
Final growth phase as baby prepares for birth. From about 14.8 inches to over 20 inches. Rapid weight gain and lung maturation occur during this period.
Key Growth Milestones
📏 Length Development
- Week 12: About 2.5 inches - fits in a walnut shell
- Week 20: About 10 inches - halfway mark
- Week 28: About 14.8 inches - fits lengthwise in your torso
- Week 40: About 20 inches - full newborn size
⚖️ Weight Development
- Week 12: About 0.5 oz - lighter than a letter
- Week 20: About 10.6 oz - less than a pound
- Week 28: About 2.2 lbs - rapid gain begins
- Week 40: About 7.6 lbs - average birth weight
🛍️ Support Your Baby's Growth — and Your Growing Bump
Comfort and preparation products other expecting parents find helpful at this stage. These are convenience picks, not medical advice — always follow your provider's guidance.
Prenatal Vitamins (with Folate & DHA)
Daily folate, iron and DHA support that doctors recommend before and throughout pregnancy.
Check Price on Amazon →DHA Omega-3 Supplement (Prenatal)
Doctors recommend DHA throughout pregnancy for baby's brain and eye development — especially the third trimester.
Check Price on Amazon →Belly Butter / Stretch-Mark Cream
Rich cocoa-butter moisturizer to keep a growing belly comfortable and hydrated.
Check Price on Amazon →What to Expect When You're Expecting
The classic week-by-week guide trusted by millions of expecting parents.
Check Price on Amazon →Amazon Associates Disclosure: As an Amazon Associate, we earn from qualifying purchases at no extra cost to you. These recommendations are editorially chosen comfort and preparation products and are not medical advice.