4 Weeks Pregnant
Summary
Size
poppy seed
Length
0.1 cm
Weight
0.4 g
Until due date
36 weeks
4 / 40 week
%10
What's Happening With Your Baby
The fertilised egg is implanting into the wall of the uterus. The embryo is made up of three layers right now, and those layers will become the nervous system, the heart and circulation, the digestive system and the skeleton. The structures that precede the placenta are forming, and hCG — the hormone that turns a pregnancy test positive — starts to be released.
What's Changing For You
Most women don't yet know they're pregnant this week. A missed period may only just be starting. Mild cramping and pink-to-brown spotting (implantation bleeding) can happen; it is usually far lighter than a period.
To Do This Week
Take a pregnancy test on the first day of your missed period, using your first morning urine.
If you haven't started folic acid yet, start today — the neural tube closes in these first weeks.
Stop smoking and drinking completely, and keep caffeine under 200 mg a day.
Frequently Asked Questions
How many months is 4 weeks pregnant?
Week 4 of pregnancy falls in month 1 and in the first trimester. Pregnancy months don't run in neat four-week blocks, so the week-to-month conversion rarely lands on a whole number — which is why pregnancy is tracked in weeks.
How big is the baby at 4 weeks?
At 4 weeks your baby is roughly the size of a poppy seed: around 0.1 cm long and 0.4 grams. These are averages; clear variation between babies is normal, and what matters is the growth curve your doctor is tracking.
How long is left at 4 weeks pregnant?
Assuming a 40-week pregnancy, you have around 36 weeks left at week 4. Most births happen between weeks 37 and 42, so a due date is a range rather than a fixed day.
What should I watch out for at 4 weeks?
Take a pregnancy test on the first day of your missed period, using your first morning urine. If you haven't started folic acid yet, start today — the neural tube closes in these first weeks. Stop smoking and drinking completely, and keep caffeine under 200 mg a day.
Track your pregnancy week by week
Baby Wallie brings your baby's weekly development, your health logs and AI-powered nutrition, sleep and breathing programs into one app. Free for 7 days.
Related Guides
When To Seek Care Immediately
Whatever week you are in, contact your doctor or the nearest health facility without waiting if you have: vaginal bleeding or fluid loss, severe persistent abdominal pain, a severe headache, blurred vision or flashing lights, sudden swelling of the hands or face, a fever above 38 °C, burning on urination with fever, persistent vomiting, fainting, or — after week 28 — a clear reduction in your baby's movements. In these situations reach real medical care rather than an app or a web search.
This content is for informational purposes only and does not replace medical advice. Always consult your doctor or midwife about your own or your baby's health.