Third trimester · This is the due week
| Fact | Week 40 |
|---|---|
| Days of pregnancy | 274–280 since LMP |
| Gestational age span | 39w0d to 39w6d |
| Trimester | Third trimester (weeks 28–40) |
| Pregnancy month | Month 3 (weeks 9–13) |
| Average length | 20.2 in (crown to heel) |
| Average weight | 7.63 lb |
| Size comparison | a small pumpkin |
| Weeks remaining | 0 (40-week due date) |
Week 40 is the due week, and only about 4 to 5 in 100 babies arrive on the exact date. The placenta is still delivering antibodies, and the baby continues growing, roughly half a pound this week.
The baby is fully developed: organs working, reflexes sharp, grasp strong. Most of the lanugo and vernix are gone, swallowed and processed. The skull plates stay flexible for delivery.
Gestationally, week 40 means you are 39 weeks and 0 to 6 days pregnant, day 274 to day 280 counted from the first day of your last period. This is week 13 of the third trimester (weeks 28–40). Appointments are weekly from week 36 until delivery. You are in the due week; from 41 weeks your provider will usually talk induction. 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 40.
Once active labor starts, eat lightly and stay hydrated. After 41 weeks providers usually discuss induction; your OB or midwife will walk you through it.
Weeks of pregnancy don't map cleanly to calendar months, but the common division puts week 40 falls in month 3 of pregnancy (weeks 9–13). Week 40 is part of the third trimester, which runs from week 28 to birth. Gestationally, week 40 means you are 39 weeks and 0 to 6 days pregnant.
At week 40 the baby averages 20.2 in long and weighs about 7.63 lb, roughly the size of a small pumpkin. 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.