4 Weeks Pregnant — Baby Is the Size of a Poppy seed
At 4 weeks you are 28 days into the 40-week count, with 252 days to go and 10% of the pregnancy behind you. Baby is about the size of a poppy seed and weighs under 0.01 g. This page fixes week 4 in place: what is developing, which appointments are still ahead, and how the week maps onto months.
10% of 280 days. The due date itself is a midpoint, not a deadline: full-term births spread across roughly weeks 37 to 42.
This week
The embryo is implanted and your body is producing the pregnancy hormone. No symptoms needed — hCG is quietly rising.
Measured in months, week 4 sits in month 1: Weeks 1–4 are counted before conception actually happens: the first two weeks are your period and the run-up to ovulation.
Appointments still ahead
| Window | Appointment | What it checks |
|---|---|---|
| 8–12 wks | Booking appointment | First scan confirms the pregnancy, due date and heartbeat. |
| 11–13 wks | NT scan (combined test) | Checks nuchal translucency and screens for chromosomal conditions. |
| 15–20 wks | Quad / anomaly blood screen | Optional blood test for screening risk factors. |
| 18–22 wks | Anatomy scan | Detailed look at baby's organs, limbs and growth — often the sex reveal. |
| 24–28 wks | Glucose tolerance test | Screens for gestational diabetes. |
| 28–34 wks | Routine growth checks | Regular midwife visits, bump measurements and blood pressure. |
| 34–36 wks | Group B strep swab | A simple swab that protects the baby during delivery. |
| 37–40 wks | Weekly checkups | Position checks, growth checks and the birth plan in earnest. |
Around week 4
| Week | Size | Weight |
|---|---|---|
| 4 | a poppy seed | under 0.01 g |
| 5 | an apple seed | under 0.01 g |
Frequently asked
What does 4 weeks pregnant mean in days and months?
4 weeks is 28 days since the first day of your last period, which is about 1 months pregnant on the four-week-per-month convention. 252 days remain in the 40-week count from here — that is 10% of the way through.
How big is a baby at 4 weeks?
Around the size of a poppy seed, at under 0.01 g. These are population averages: a scan measurement that differs by a few days is normal and does not by itself mean anything is wrong.
Which trimester is week 4?
The 1st trimester. The split used here is the same one the calculator applies: the first trimester covers days 1–90, the second 91–195, and the third from day 196 onward. Other sources draw the boundary a week either side, which is why week 13 and week 14 can both be described as "end of the first trimester".
What appointments happen after week 4?
Next up: Booking appointment at 8–12 weeks, NT scan (combined test) at 11–13 weeks, Quad / anomaly blood screen at 15–20 weeks. The full schedule is in the table above; exact timing varies by country and by your care team.