31 Weeks Pregnant — Baby Is the Size of a Coconut
At 31 weeks you are 217 days into the 40-week count, with 63 days to go and 78% of the pregnancy behind you. Baby is about the size of a coconut and weighs about 24.5 g. This page fixes week 31 in place: what is developing, which appointments are still ahead, and how the week maps onto months.
78% 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
Baby turns its head from side to side and its organs — especially lungs — mature quickly. Fat layers plump it up.
Measured in months, week 31 sits in month 8: Month eight is about position and preparation: growth scans, the birth plan, and the bag by the door.
Appointments still ahead
| Window | Appointment | What it checks |
|---|---|---|
| 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 31
| Week | Size | Weight |
|---|---|---|
| 30 | a cabbage | about 23 g |
| 31 | a coconut | about 24.5 g |
| 32 | a jicama | about 26 g |
Frequently asked
What does 31 weeks pregnant mean in days and months?
31 weeks is 217 days since the first day of your last period, which is about 8 months pregnant on the four-week-per-month convention. 63 days remain in the 40-week count from here — that is 78% of the way through.
How big is a baby at 31 weeks?
Around the size of a coconut, at about 24.5 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 31?
The 3rd 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 31?
Next up: Group B strep swab at 34–36 weeks, Weekly checkups at 37–40 weeks. The full schedule is in the table above; exact timing varies by country and by your care team.