At 40 weeks pregnant you have reached the usual due date. Weeks are counted from the first day of your last period. Many babies arrive a little before or after this date, and your doctor will guide you on timing.
How big is your baby at 40 weeks?
Around week 40, your baby is often compared to a small watermelon. Fruit and vegetable comparisons are a friendly way to picture the size, not an exact measurement.
From the INTERGROWTH-21st international standard (University of Oxford), the median estimated fetal weight at 40 weeks is about 3.34 kg. Most healthy babies fall between roughly 2.50 kg and 4.17 kg (about the 2nd to 98th percentile). Scan estimates carry some margin of error, so a number on its own is rarely a reason to worry. Our guide on reading the weight on your scan report explains more, and the baby weight checker lets you enter your own report.
The third trimester runs from week 28 until birth. The baby gains most of its weight now, and your body prepares for labour.
Your body at 40 weeks
Due date week. Only a small share of babies arrive on the day. If you go past it, your doctor will plan next steps.
What is going on
Due date. Only a small share of babies are born on the day, and a few more days or a week or two is not unusual. Your doctor will plan monitoring and, if needed, induction.
What can help
Stay in touch with your doctor, keep moving gently and keep counting movements.
Other weeks
38 weeks pregnant ยท 39 weeks pregnant
See all weeks on the pregnancy week by week page, or try the interactive week-by-week guide.