Pregnancy Week 40: Due Date + Labor Signs

Welcome to your due date week. If baby has arrived, congratulations — you can stop reading and go stare at them. If they haven't, welcome to the club that most first-time parents join: pregnancy that goes a little past the estimated date. Around 60% of first babies arrive after their due date, and that's completely normal.

This guide walks through what's happening at 40 weeks pregnant, how to spot real labor, exactly when to go to the hospital, hospital bag reminders, and what happens if baby takes their sweet time.

This article is educational, not medical advice. Pregnancy is deeply individual, and your obstetrician or midwife is the person who knows your history. We're the team behind Vyve, the private AI pregnancy and cycle tracker, and Vyve is a tracking tool — not a diagnostic one.

What's happening this week

You've made it. Baby is fully developed and just waiting for the signal to leave. Appointments are typically weekly at this point and may include monitoring — non-stress tests, ultrasounds — especially if you cross into week 41. Cervical checks may be offered if you want to know whether things are progressing.

Most first babies arrive within two weeks of the due date, with more arriving after than before. If you want a refresher on how due dates are calculated, our due date calculator walks through it.

Baby's size and development at week 40

At 40 weeks pregnant, your baby is about the size of a watermelon or a small pumpkin — roughly 51 centimeters (20 inches) from head to heel, weighing around 3.5 kilograms (7.7 pounds). Sizes vary a lot; average birth weight range is roughly 2.7 to 4 kilograms.

Baby is fully developed:

• All organs mature. Lungs, brain, digestive system, immune system — all ready.
• Skull remains slightly flexible to allow moulding during birth.
• Vernix and lanugo are mostly gone, though some may still be present.
• Meconium is in the intestines, ready to be the first stool.
• Baby is in position — head-down and often engaged in the pelvis.
• Movement is limited but should be present — count kicks daily.

The due date isn't a deadline

Only about 4 to 5% of babies arrive on their actual due date. Most come within a two-week window (weeks 38 through 42), and first babies are more likely to be later. Your due date is a best estimate, calculated from your last menstrual period or first-trimester ultrasound; it's not a deadline your body ignored.

Terminology reminder: 39–40+6 is "full term," 41 weeks is "late term," and 42+ is "post-term." Most clinicians discuss induction around 41 weeks and typically offer it by 42, but the exact threshold and approach is a conversation with your team.

Your symptoms and body changes

Common experiences:

• Pelvic pressure. Baby is low and heavy.
• Frequent Braxton Hicks or early labor contractions.
• Loss of mucus plug or bloody show.
• Diarrhea. Some people notice loose stools in the days before labor — the body is emptying out.
• Nesting or the opposite. Sudden urge to organize, or total exhaustion.
• Trouble sleeping.
• Back and hip pain.
• Emotional intensity. Excitement, impatience, anxiety, wonder, grumpiness — often all in an hour.
• Increased vaginal discharge.
• Colostrum leakage.

Real labor vs Braxton Hicks

Common rule: 5-1-1 for first-time labor — contractions 5 minutes apart, each 1 minute long, for at least 1 hour. Second and later births often use 4-1-1. Follow your clinician's specific guidance.

Waters breaking

Not everyone's waters break dramatically — for many people, it's a small trickle rather than a gush, or it happens during labor rather than at the start. Here's what to know:

• Call your clinician as soon as it happens, even if you're not having contractions.
• Note the time — it matters for infection risk timing.
• Note the color — clear or straw-colored is expected. Greenish or brownish (meconium) needs urgent evaluation. Bright red bleeding is also urgent.
• Note the smell — a foul odor could suggest infection.
• Wear a pad (not a tampon) so you can monitor.

Contractions usually follow within 24 hours, but not always. Many clinicians recommend delivering within 12 to 24 hours of waters breaking because infection risk rises, so if labor doesn't kick in on its own, induction may be discussed.

Hospital bag reminders

Bag should be by the door. Quick check:

For you: ID, insurance, birth plan (printed), loose clothes, robe, non-slip socks, nursing bras, heavy-flow pads, toiletries, phone charger with long cable, pillow from home, snacks and drinks (for after labor), comfort items.

For baby: Going-home outfit, hat, socks, swaddle blanket, diapers and wipes, installed car seat.

For partner: Change of clothes, toiletries, snacks, phone charger, pillow if staying overnight, camera.

Ready to go: Car seat installed, hospital route saved in maps, gas in the car, phone numbers saved.

When to call your doctor

Call now (or head to the hospital) if you have:

• Regular painful contractions per your team's rule (usually 5-1-1)
• Waters breaking — any gush or persistent leak, even without contractions
• Any bleeding heavier than light spotting
• Decreased fetal movement — noticeable drop from baby's normal pattern
• Severe headache with vision changes or upper abdominal pain (possible preeclampsia — always urgent)
• Sudden severe swelling of face or hands
• Fever above 38°C / 100.4°F
• Severe or one-sided abdominal pain
• Greenish, brownish, or bloody amniotic fluid
• Fainting or persistent dizziness
• Anything that feels seriously wrong — trust your instincts

If you go past your due date

Most first babies do. Here's the typical pathway:

• 40–41 weeks: Increased monitoring may start. Cervical checks, non-stress tests, ultrasound to check amniotic fluid and baby's wellbeing.
• 41 weeks: Induction is commonly discussed. Some people prefer to wait; others opt in. There's real evidence for and against; it's a conversation.
• 42 weeks: Induction is typically offered because risks (stillbirth, meconium aspiration, placental function) start to rise. Rarely does a pregnancy go past 42 weeks in developed care.

Natural methods to encourage labor (walking, sex, nipple stimulation, spicy food) are widely discussed but their evidence is mixed. Talk to your clinician about what's reasonable for you.

3 tips for this week

1. Distract yourself. Watch a series. Cook a favorite meal. Take short walks. The waiting is the hardest part; give yourself something to focus on.
2. Time contractions when they come. Vyve makes this easy — tap start, tap stop, see the pattern build.
3. Keep counting kicks. This matters right up until labor. Any noticeable decrease in movement is a call-your-clinician-now situation.

How Vyve helps you track your pregnancy

Vyve is a privacy-first AI pregnancy and cycle tracker built for people who don't want their body's most personal data sold to advertisers. At 40 weeks, Vyve helps you time contractions, log kick counts, and prepare for the transition into postpartum tracking — all on your device.

Vyve runs its AI on your device, encrypts your data, and doesn't require an account. Your pregnancy is yours.

Frequently asked questions

How big is baby at 40 weeks pregnant?

At 40 weeks, baby is about the size of a watermelon or a small pumpkin — roughly 51 centimeters (20 inches) from head to heel, and weighing around 3.5 kilograms (7.7 pounds). Every baby is different; the average birth weight range is roughly 2.7 to 4 kilograms.

What percentage of babies are born on their due date?

Only about 4 to 5% of babies are born on their actual due date. Most arrive within a two-week window around it — some earlier, some later. The due date is a best estimate, not a deadline.

What are the signs of labor at 40 weeks?

The main signs are: regular contractions that get progressively closer and stronger, waters breaking (gush or persistent leak), bloody show or loss of the mucus plug, and lower back pain that wraps around to the front. Real labor doesn't stop with rest or hydration. Your clinician's guidance for when to call (often 5-1-1 for first-time labor) is the rule to follow.

When should waters breaking mean I go to the hospital?

Call your clinician as soon as your waters break, even if you're not having contractions. They'll tell you when to come in based on your specific situation — often within 12 to 24 hours if contractions don't start on their own, because the protective barrier is gone and infection risk increases. Note the time, the color of the fluid, and any odor to report.

What happens if I go past my due date?

Going a few days past your due date is completely normal. From about 41 weeks, your clinician will typically increase monitoring — non-stress tests, ultrasound to check amniotic fluid and baby's wellbeing. Induction is often discussed around 41 weeks and typically offered by 42 weeks because risks start to rise. This is a conversation with your team, not a fixed rule.

This article is educational and not medical advice. Always consult your obstetrician or midwife for personal medical guidance.