40 Weeks Pregnant — Baby Is the Size of a Watermelon
At 40 weeks you are 280 days into the 40-week count, with 0 days to go and 100% of the pregnancy behind you. Baby is about the size of a watermelon and weighs about 39.8 g. This page fixes week 40 in place: what is developing, which appointments are still ahead, and how the week maps onto months.
100% 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
Due date week. Most babies arrive within two weeks either side of this date — you're at the finish line.
Measured in months, week 40 sits in month 9: The final month: weekly checks, a due date that is a midpoint rather than a deadline, and full-term from week 37.
Appointments still ahead
No routine screening remains in the standard schedule — from here it is monitoring rather than testing.
Around week 40
| Week | Size | Weight |
|---|---|---|
| 39 | a pumpkin | about 38.2 g |
| 40 | a watermelon | about 39.8 g |
| 41 | a small watermelon | about 41.2 g |
Frequently asked
What does 40 weeks pregnant mean in days and months?
40 weeks is 280 days since the first day of your last period, which is about 9 months pregnant on the four-week-per-month convention. 0 days remain in the 40-week count from here — that is 100% of the way through.
How big is a baby at 40 weeks?
Around the size of a watermelon, at about 39.8 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 40?
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 40?
The routine schedule ends at 40 weeks. From here the focus is monitoring: position checks, growth checks and a discussion about induction if the pregnancy runs past 41 weeks.