--- title: "40 weeks pregnant: baby the size of a watermelon | PERIOD." description: "40 weeks pregnant: your baby is the size of a watermelon, about 51.2 cm and 3.6 kg. What happens this week for your baby and in your body." url: https://myperiod.app/en/pregnancy/40-weeks-pregnant lang: en publisher: PERIOD. B.V., Amsterdam --- [Pregnancy week by week](https://myperiod.app/en/pregnancy) # 40 weeks pregnant At 40 weeks you are in month 9 and the third trimester. Your baby is about the size of a watermelon: 51.2 cm and 3.6 kg. As big as watermelon Length 51.2 cm Weight 3.6 kg Month 9 Trimester third trimester To go due Averages. Measured crown to rump up to week 20, crown to heel after that. Healthy babies vary a lot. ## Your baby this week The due date. Though only a small share arrive exactly today. ## Your body It can start any day now; everything may stand ready. ## Good to know The due date is an estimate of a window, not a deadline. ## To sort around these weeks - You are close to or at your due date: rest where you can. - After 41 weeks your midwife talks you through the next steps. [Work out your due date](https://myperiod.app/en/tools/due-date-calculator)[How many weeks pregnant am I?](https://myperiod.app/en/tools/pregnancy-week-calculator) ## Follow your pregnancy week by week In PERIOD. baby you see every week how big your baby is, what is happening and what you can arrange. No ads, and we never sell your data. 4.8 ★★★★★ on the App Store 100,000+ women ## Frequently asked questions ### How many months is 40 weeks pregnant? 40 weeks pregnant falls in month 9 of your pregnancy. ### Which trimester is 40 weeks? At 40 weeks you are in the third trimester. ### How big is a baby at 40 weeks? On average 51.2 cm, about the size of a watermelon. Healthy babies vary a lot. ### How long to go at 40 weeks? You are due. A birth between 37 and 42 weeks counts as on time. ## [All weeks](https://myperiod.app/en/pregnancy) - [4](https://myperiod.app/en/pregnancy/4-weeks-pregnant) - [5](https://myperiod.app/en/pregnancy/5-weeks-pregnant) - [6](https://myperiod.app/en/pregnancy/6-weeks-pregnant) - [7](https://myperiod.app/en/pregnancy/7-weeks-pregnant) - [8](https://myperiod.app/en/pregnancy/8-weeks-pregnant) - [9](https://myperiod.app/en/pregnancy/9-weeks-pregnant) - [10](https://myperiod.app/en/pregnancy/10-weeks-pregnant) - [11](https://myperiod.app/en/pregnancy/11-weeks-pregnant) - [12](https://myperiod.app/en/pregnancy/12-weeks-pregnant) - [13](https://myperiod.app/en/pregnancy/13-weeks-pregnant) - [14](https://myperiod.app/en/pregnancy/14-weeks-pregnant) - [15](https://myperiod.app/en/pregnancy/15-weeks-pregnant) - [16](https://myperiod.app/en/pregnancy/16-weeks-pregnant) - [17](https://myperiod.app/en/pregnancy/17-weeks-pregnant) - [18](https://myperiod.app/en/pregnancy/18-weeks-pregnant) - [19](https://myperiod.app/en/pregnancy/19-weeks-pregnant) - [20](https://myperiod.app/en/pregnancy/20-weeks-pregnant) - [21](https://myperiod.app/en/pregnancy/21-weeks-pregnant) - [22](https://myperiod.app/en/pregnancy/22-weeks-pregnant) - [23](https://myperiod.app/en/pregnancy/23-weeks-pregnant) - [24](https://myperiod.app/en/pregnancy/24-weeks-pregnant) - [25](https://myperiod.app/en/pregnancy/25-weeks-pregnant) - [26](https://myperiod.app/en/pregnancy/26-weeks-pregnant) - [27](https://myperiod.app/en/pregnancy/27-weeks-pregnant) - [28](https://myperiod.app/en/pregnancy/28-weeks-pregnant) - [29](https://myperiod.app/en/pregnancy/29-weeks-pregnant) - [30](https://myperiod.app/en/pregnancy/30-weeks-pregnant) - [31](https://myperiod.app/en/pregnancy/31-weeks-pregnant) - [32](https://myperiod.app/en/pregnancy/32-weeks-pregnant) - [33](https://myperiod.app/en/pregnancy/33-weeks-pregnant) - [34](https://myperiod.app/en/pregnancy/34-weeks-pregnant) - [35](https://myperiod.app/en/pregnancy/35-weeks-pregnant) - [36](https://myperiod.app/en/pregnancy/36-weeks-pregnant) - [37](https://myperiod.app/en/pregnancy/37-weeks-pregnant) - [38](https://myperiod.app/en/pregnancy/38-weeks-pregnant) - [39](https://myperiod.app/en/pregnancy/39-weeks-pregnant) - [40](https://myperiod.app/en/pregnancy/40-weeks-pregnant) - [41](https://myperiod.app/en/pregnancy/41-weeks-pregnant) - [42](https://myperiod.app/en/pregnancy/42-weeks-pregnant) General information, not medical advice. If in doubt, call your midwife or GP. Sources: WHO fetal growth charts (Kiserud et al., PLoS Med 2017); Robinson and Fleming 1975; NHS, Your pregnancy and baby guide.