Third trimester · 9 weeks to go
| Fact | Week 31 |
|---|---|
| Days of pregnancy | 211–217 since LMP |
| Gestational age span | 30w0d to 30w6d |
| Trimester | Third trimester (weeks 28–40) |
| Pregnancy month | Month 3 (weeks 9–13) |
| Average length | 16.2 in (crown to heel) |
| Average weight | 3.31 lb |
| Size comparison | a coconut |
| Weeks remaining | 9 (40-week due date) |
Week 31 connects the senses: all five are now operational, and the brain is wiring connections between them at high speed. The baby can perceive information from all senses simultaneously.
Fat fills the arms and legs. The uterus is crowded enough that flips become slow rolls, and sharp jabs under the ribs become common. The placenta continues supplying antibodies that protect the baby now and after birth.
Gestationally, week 31 means you are 30 weeks and 0 to 6 days pregnant, day 211 to day 217 counted from the first day of your last period. This is week 4 of the third trimester (weeks 28–40). Appointments step up to every two weeks from week 28. Week 32 brings the Tdap vaccine window (27–36 weeks) winding down. From here the baby gains roughly half a pound a week on average, which is why the third trimester feels measurably heavier by the day. Every number on this page is an average across pregnancies; your own scan dates and your baby's measurements are what actually describe your week 31.
Count kicks at the same time daily. If movements seem reduced, drink something cold, rest, and recheck before calling.
Weeks of pregnancy don't map cleanly to calendar months, but the common division puts week 31 falls in month 3 of pregnancy (weeks 9–13). Week 31 is part of the third trimester, which runs from week 28 to birth. Gestationally, week 31 means you are 30 weeks and 0 to 6 days pregnant.
At week 31 the baby averages 16.2 in long and weighs about 3.31 lb, roughly the size of a coconut. Sizes come from fetal growth charts (crown-to-heel length from week 20), and normal variation week to week is wide; your ultrasound measurements always outrank a chart.