Week 40
Your baby is the size of a watermelon
Today is your due date. Per Jukic et al. (Hum Reprod, 2013), only 4% of women deliver at exactly 280 days, and about 70% deliver within 10 days of the estimate. Pregnancy length naturally varies up to 37 days even after excluding complications. Here's what week 40 actually is, what the evidence says about waiting versus inducing at 41 weeks, and the monitoring plan that kicks in next.
Key takeaways
- Only 4% of women deliver on the exact due date per Jukic et al. (Hum Reprod, 2013). About 70% deliver within 10 days of the estimate. Pregnancy length naturally varies by up to 37 days even when conception is precisely dated.
- Stillbirth risk rises from 0.11 to 3.18 per 1000 pregnancies between 37 and 42 weeks per Muglu et al. (PLOS Med, 2019). The 40-to-41 week step is a 64% relative increase. Absolute risk stays small. Direction is real.
- Induction at or beyond term reduces perinatal death (RR 0.31) per Middleton et al. (Cochrane, 2020), based on 22 trials and 18,795 infants. SWEPIS (BMJ, 2019) was stopped early when six perinatal deaths occurred in expectant management (n=1,379) versus zero in the 41-week induction arm (n=1,381).
- Twice-weekly antepartum testing kicks in at 41 weeks per ACOG Practice Bulletin #146. The standard pairing is a non-stress test plus an amniotic-fluid check.
Today is the due date, and most babies do not arrive exactly today.
Per Jukic et al. (Hum Reprod, 2013), only 4% of women deliver at exactly 280 days of gestation. About 70% deliver within 10 days of the estimate.
The same study, restricted to spontaneously conceived pregnancies with ovulation precisely dated, found gestational length spanned 37 days even after excluding women with complications or preterm births.
Translation: the due date is the middle of a normal range. Not a deadline.
Your baby is fully built by now. Lungs are mature. The brain has been adding mass through the third trimester. Subcutaneous fat is in place for temperature regulation in the first hours after delivery. Vernix lingers mostly in skin folds, and lanugo is essentially gone.
What changes this week is space. The amniotic sac is full. Big kicks are pushes, stretches, and rolls.
Daily movement should still feel consistent.
Count 10 movements within two hours during your baby's active window. If you don't reach it, lie on your left side, drink something cold, and try again. If you still don't, call your provider. Sustained decreased movement at term is always worth a call.
From your side, the work is mostly waiting now. What your baby needs after delivery is the next big shift: a muslin swaddle for the going-home photo, a sleeper gown for the first nights at home, and the start of feeding within an hour of birth.
Why your provider will offer induction at 41 weeks, and what the actual evidence says
ACOG drew the lines at Week 39: late term is 41 weeks, postterm is 42 weeks and beyond per Practice Bulletin #146.
Here's the evidence behind why providers offer induction in the 41-to-42 week window.
Per Muglu et al. (PLOS Med, 2019), in a meta-analysis of 15 million pregnancies, stillbirth risk rose from 0.11 to 3.18 per 1000 between 37 and 42 weeks. The 40-to-41 week step was a 64% relative increase. One additional stillbirth for every 1,449 women who continued past 40 weeks.
Per Middleton et al. (Cochrane, 2020), induction at or beyond term reduced perinatal death (RR 0.31, 95% CI 0.15 to 0.64) across 22 trials and 18,795 infants.
Two stillbirths in the induction arm. Sixteen in expectant management.
SWEPIS (BMJ, 2019) was halted early when six perinatal deaths occurred in expectant management (n=1,379) versus zero in the 41-week induction arm (n=1,381).
Per ACOG #146, twice-weekly antepartum testing kicks in at 41 weeks. The standard pairing is a non-stress test plus an amniotic-fluid check. Induction is recommended after 42 weeks and no later than 42 weeks and 6 days.
Contact your provider right away if you have heavy bleeding, fluid leakage, severe headache or vision changes, upper-belly pain, or a sustained drop in your baby's movement.
For dads
Here's your move:
Stage the labor-day playbook this weekend. The hospital bag has been in the car since Week 36. Confirm the charger and a power strip are with it. Your phone has to last two days, and so does hers. Top off the gas tank. Save the L&D direct line one tap away. For 'any news?' texts, draft one auto-reply: 'We'll let everyone know.' Close the thread. Take a walk together every day for the next week. Or use a birthing ball at home for gentle hip rocking. Not to start labor. Walking and rocking won't reliably do that. The reason is to break the watching-the-clock loop.
Real talk:
Skip 'almost there.' She's heard it for three weeks. The word 'almost' covers anywhere from today to ten more days, and that range is brutal when every hour feels like a day. What actually lands: match her pace. If she wants to talk, listen. If she wants quiet, sit with her quietly. Postpartum recovery starts the moment your baby arrives. The recovery kit, the perineal spray, the mesh underwear: those are her first 24 hours. If breastfeeding is the plan, the nipple butter and the disposable nursing pads go in the same zipped pocket. Knowing where everything is in the bag is your job, not hers.
Common concerns
I'm at my due date and nothing's happening. Is something wrong?+
Almost certainly not. Per Jukic et al. (Hum Reprod, 2013), only 4% of women deliver at exactly 280 days, and 70% deliver within 10 days of the estimate. Your provider will increase monitoring at 41 weeks and discuss induction in the 41-to-42 week window per ACOG Practice Bulletin #146.
What does antepartum testing at 41 weeks actually look like?+
Per ACOG #146, twice-weekly testing typically pairs a non-stress test (NST) with an amniotic-fluid check, also called a modified biophysical profile. The NST monitors your baby's heart rate and movement for about 20 to 40 minutes. The fluid check uses ultrasound to confirm there's enough amniotic fluid. Both are painless.
Should I ask for a membrane sweep at 40 weeks?+
It's a reasonable conversation to have. We covered the effect sizes at Week 38, so the short version: modest, real, worth asking about. Whether a sweep is even possible depends on whether your cervix has started to open. Your provider will check. It's brief and mildly uncomfortable, not magic.
Can I wait past 41 weeks if I want to?+
Talk it through with your provider. Per Middleton et al. (Cochrane, 2020), a policy of induction at or beyond term reduced perinatal death (RR 0.31). Per Muglu et al. (PLOS Med, 2019), stillbirth risk rose from 0.11 to 3.18 per 1000 between 37 and 42 weeks. ACOG #146 recommends induction no later than 42 weeks and 6 days. Shared decision making is the standard.
Product picks for week 40
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Frida Mom 11pc Postpartum Essentials Kit
Peri bottle, ice maxi pads, healing foam, disposable underwear, and pad liners in one box. The grab-and-go postpartum recovery bundle for the first 24 hours.
Mesh Postpartum Underwear 6 Pack
Reusable mesh briefs for the first weeks of bleeding. A budget pick that pairs with the postpartum kit.
BABYGO Birthing Ball with Exercise Book Set
65 cm anti-burst birthing ball with a pregnancy-specific exercise guide. The exact tool for the gentle hip rocking that may help the baby descend during the wait.
Sources
- Jukic AM et al., Length of human pregnancy and contributors to its natural variation (Hum Reprod, 2013) — https://pmc.ncbi.nlm.nih.gov/articles/PMC3777570/
- Muglu J et al., Risks of stillbirth and neonatal death with advancing gestation at term: A systematic review and meta-analysis of 15 million pregnancies (PLOS Med, 2019) — https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002838
- Middleton P et al., Induction of labour at or beyond 37 weeks gestation (Cochrane Database Syst Rev, 2020) — https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD004945.pub5/full
- Wennerholm UB et al., Induction of labour at 41 weeks versus expectant management and induction of labour at 42 weeks (SWEPIS), BMJ 2019;367:l6131 — https://pubmed.ncbi.nlm.nih.gov/31748223/
- ACOG, Management of Late-Term and Postterm Pregnancies (Practice Bulletin No. 146, August 2014) — https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2014/08/management-of-late-term-and-postterm-pregnancies
- ACOG, When Pregnancy Goes Past Your Due Date (Patient FAQ) — https://www.acog.org/womens-health/faqs/when-pregnancy-goes-past-your-due-date
A quick note: This content is for informational purposes only and is not a substitute for professional medical advice. Always talk to your healthcare provider about any questions or concerns. Content based on guidance from the American College of Obstetricians and Gynecologists (ACOG), the American Academy of Pediatrics (AAP), Mayo Clinic, and peer-reviewed medical literature. Learn how we create our content.