Week 3
Your baby is the size of a Poppy seed
Baby Size
Poppy seed
Length
—
Weight
—
Trimester
First Trimester
Your Baby at Week 3
Week 3 is when conception actually happens. The fertilized egg (now called a zygote) travels down the fallopian tube and begins dividing into multiple cells.
Key milestone: Fertilization and implantation. The zygote travels to the uterus.
Your Symptoms
Very early pregnancy signs: light spotting (implantation bleeding), breast tenderness.
Tip for This Week
Rest when you can. Your body is doing extraordinary work at a cellular level.
Your Body at Week 3
During the first trimester, your body is working overtime to build the placenta and support rapid embryonic development. Hormones like hCG, estrogen, and progesterone surge, causing many of the symptoms you're experiencing. Your blood volume is already increasing, and your uterus is beginning to expand — even if you can't see it yet.
Your baby at week 3 is the size of a Poppy seed, measuring about — and weighing roughly —. The focus is on forming all major organ systems that will sustain your baby through the rest of pregnancy and beyond.
Your Baby's Development This Week
Week 3 is when conception actually happens. The fertilized egg (now called a zygote) travels down the fallopian tube and begins dividing into multiple cells. The key milestone this week is that fertilization and implantation. the zygote travels to the uterus.
The first trimester is a period of incredible transformation. From a single cell to a fully formed fetus in just 12 weeks — your baby's development is happening at an astonishing pace. Each week brings new organs, new abilities, and new reasons to marvel at the process.
This week's voice theme
“Settling in — finding home.”
Imagine hearing this every morning — a voice note from your baby that evolves week by week.
Hear your baby's voice →Frequently Asked Questions
What is implantation bleeding?
Light spotting that can occur when the fertilized egg attaches to the uterine lining, usually around 6-12 days after conception.
Can I feel implantation?
Some women experience mild cramping or light spotting during implantation, but many feel nothing at all.