you're 3 weeks pregnant.
last revised · baby is about 0.06 cm (0.02") · 0.02 g (0.00 oz)
At 3 weeks pregnant, your baby is about 0.06 cm and 0.02 g — A cluster of cells (the morula and then blastocyst) is drifting through the fallopian tube on its way to the uterus.
about the size of a…
A cluster of cells (the morula and then blastocyst) is drifting through the fallopian tube on its way to the uterus.
this week's highlights
- Rapid cell division
- Blastocyst forms
- Heading to the uterus
- Inner cell mass appears
how your baby looks
A hollow ball of about 100 cells called a blastocyst. The inner cells will become the embryo; the outer cells will become the placenta.
body in focus
- head
- body
- A hollow ball of about 100 cells, split between future embryo and future placenta.
- hands
- feet
what's happening in your body
Hormones are quietly shifting. A few people notice a slight twinge during implantation late in week 3, but most feel nothing yet.
symptoms at 3 weeks
- No symptoms at all
- The fertilised egg is still travelling to the uterus, so most people feel nothing this week. An absence of symptoms says nothing about whether conception happened.
- Mild bloating
- Rising progesterone after ovulation slows digestion slightly, which can leave you feeling puffy. It happens whether or not you conceived, so it is not a reliable clue.
- Breast fullness
- Progesterone keeps breasts feeling heavy or tender in the second half of any cycle. In a conception cycle, this simply continues rather than fading.
- Faint twinges low in the belly
- Some people report tiny flickers of sensation late this week as the blastocyst nears the uterine wall. These are subtle at most and easy to miss.
- Heightened smell or taste changes
- A few people swear they noticed a metallic taste or sharper sense of smell before their test turned positive. Hormones are shifting, but evidence for symptoms this early is thin.
- Severe one-sided pain — when to call
- Sharp, persistent pain on one side, especially with shoulder-tip pain or bleeding, needs urgent attention as it can signal an ectopic pregnancy. Call your doctor or emergency services straight away.
gentle tips
- Stay hydrated — your blood volume is starting to ramp up.
- Skip any new medications without checking with your doctor first.
- Avoid raw fish, unpasteurized dairy, and undercooked meat from now on.
- Note the date of your last period — you'll need it for due-date math.
your week 3 checklist
- Behave as though pregnant — no alcohol, no smoking, caffeine under 200 mg a day
- Keep taking folic acid every day
- Check your kitchen for foods to pause: raw fish, unpasteurised cheese, undercooked meat, liver
- Resist testing yet — a home test cannot detect anything until implantation produces hCG
what to expect next
By the end of next week the blastocyst burrows into the uterine wall — implantation. Some women notice light spotting then.
common questions at week 3
How big is the baby at 3 weeks?
At 3 weeks, the baby measures about 0.06 cm and weighs approximately 0.02 g (0.06 cm (0.02") · 0.02 g (0.00 oz)).
What is developing at 3 weeks?
A hollow ball of about 100 cells called a blastocyst. A hollow ball of about 100 cells, split between future embryo and future placenta. Key milestones this week include: Rapid cell division; Blastocyst forms; Heading to the uterus; Inner cell mass appears.
What symptoms are common at 3 weeks pregnant?
Hormones are quietly shifting. A few people notice a slight twinge during implantation late in week 3, but most feel nothing yet.
What should I do at 3 weeks pregnant?
By the end of next week the blastocyst burrows into the uterine wall — implantation. Stay hydrated — your blood volume is starting to ramp up. Skip any new medications without checking with your doctor first. Avoid raw fish, unpasteurized dairy, and undercooked meat from now on.
How soon after conception does implantation happen?
The fertilised egg typically implants in the uterine wall six to ten days after ovulation, most commonly around day eight or nine. Only after implantation does the body start producing hCG, the hormone pregnancy tests detect. That is why testing before your missed period so often gives a false negative.
Can I feel conception or implantation happening?
Conception itself produces no sensation at all. Around implantation, a minority of people notice a faint twinge or a day of light spotting, but most feel nothing whatsoever. Feeling nothing this week is entirely normal and not a sign that anything went wrong.
Does anything I do in week 3 affect whether implantation succeeds?
Normal daily life — exercise, working, lifting your toddler, having sex — does not dislodge a blastocyst or prevent implantation. Whether implantation succeeds mostly comes down to chromosomal factors outside anyone's control. The helpful things are the quiet ones: folic acid, no alcohol, no smoking.
helpful tools
- Due Date Calculator
Find your estimated due date from your last period or conception date.
- Baby Names
Start exploring names — an early, joyful ritual.
Medically aligned with guidance from WHO, NHS and ACOG. How we write.