40 Weeks Pregnant: Baby Size, Symptoms and What to Do

Your baby this week

Your baby is full term and short on space, but should keep moving in the usual pattern.

Week 40 is your estimated due date, but only a small share of babies arrive on that exact day: most are born between 37 and 42 weeks. Your baby is fully mature, and although space is tight, the usual movement pattern should continue. Your provider will talk with you about next steps if labor hasn't started, which may include extra monitoring such as a nonstress test. If your baby moves less, don't wait for your next appointment; call right away. Waiting can be hard. Walking, rest and distractions may help you cope, but home tricks to start labor don't have reliable evidence behind them.

By the numbers

Week 40 covers days 280 to 286 counted from the first day of your last period, which is 100% of a 40-week pregnancy. Since last week, an average baby gains about 7.8 oz (220 g). By date of conception, your baby is about 38 weeks old.

Pregnancy is dated from the first day of your last period, so conception happens around week 2. Your due date is 280 days (40 weeks) from that day, and an early ultrasound may adjust it.

Your body

Your due date is an estimate, and plenty of babies arrive before or after it. If movements slow down or stop, call labor and delivery right away, any time of day.

Tests and to-dos this week

If you're still pregnant at your due date, your provider will talk with you about extra monitoring and what comes next.

• Weekly visits · weeks 36–40 · visit

Signs of labor: when to go in

Labor usually starts with contractions that come at regular intervals and get longer, stronger and closer together; they don't ease when you rest or change position. Your water may break with a gush or a slow trickle, and you may notice a bloody show. Agree with your provider on when to call: many practices use the 5-1-1 rule of thumb (contractions about every 5 minutes, lasting about 1 minute, for 1 hour). Go in right away for bleeding, green or brown fluid, a severe headache, constant pain or fewer movements. A contraction timer helps you track the pattern without doing the math.

Contraction timer

Tips for the third trimester

• From 28 weeks, go to sleep on your side; if you wake on your back, just roll over.
• Pack your hospital bag and agree with your provider on when to head in.
• Call right away, even at night, if your baby moves less or differently.
• Know the signs of labor: regular, strengthening contractions, your water breaking or a bloody show.

Last week and next week

Last week (39): The outer layer of skin has thickened.

Next week (41): The average baby now weighs around 3 to 4 kg (about 6.6 to 8.8 pounds), and the big growth spurts are over.

Frequently asked questions