A pregnancy app might still call 37 weeks "full term" while your OB calls it "early term," and the app is using the label that ACOG and maternal-fetal medicine specialists endorsed replacing in 2013.
Is 37 weeks full term? No. This guide goes week by week from 34 to 42 and lists questions to take to your next appointment. If you don't know your week yet, see which week you're in with our due date calculator.
No. Since 2013, 37 and 38 weeks have been called "early term," and full term runs from 39 weeks 0 days to 40 weeks 6 days (ACOG). A due date is an estimate, so ask your provider which week your pregnancy is in.
Key Takeaways
- 37 weeks is early term. Full term is 39 weeks 0 days through 40 weeks 6 days (ACOG, reaffirmed 2025).
- A birth before 37 weeks is preterm, and ACOG calls 34 to 36 weeks "late preterm."
- Without a medical reason, ACOG advises against a planned birth before 39 weeks, by induction or scheduled cesarean.
- With a medical or obstetric indication for an earlier birth, ACOG says not to defer delivery to the 39th week.
- Your week depends on your due date, which is an estimate.
Is 37 Weeks Full Term?
No. In November 2013, ACOG and the Society for Maternal-Fetal Medicine (SMFM) endorsed replacing the single label "term" with four names for births from 37 weeks on. ACOG reaffirmed Committee Opinion 579 in 2025, so these are the current definitions:
- Early term: 37 weeks 0 days through 38 weeks 6 days
- Full term: 39 weeks 0 days through 40 weeks 6 days
- Late term: 41 weeks 0 days through 41 weeks 6 days
- Postterm: 42 weeks 0 days and beyond
A birth before 37 weeks is preterm, according to ACOG and the CDC, and the CDC counted 10.4% of US births as preterm in 2022. ACOG calls 34 weeks 0 days through 36 weeks 6 days "late preterm." You'll see these written as "37 0/7" or "37+0" (37 weeks, 0 days).
Full Term, Week by Week: 34 to 42 Weeks
A medical reason can change the timing in the last column.
| The question | Answer | What it means | Timing guidance |
|---|---|---|---|
| Is 34 weeks full term? | No, late preterm | Preterm: before 37 weeks | ACOG: no planned birth before 39 weeks without a medical reason |
| Is 35 weeks full term? | No, late preterm | Preterm | As at 34 weeks |
| Is 36 weeks full term? | No, late preterm | Last preterm week | As at 34 weeks |
| Is 37 weeks full term? | No, early term | First early-term week | As at 34 weeks |
| Is 38 weeks full term? | No, early term | Last early-term week | As at 34 weeks |
| Is 39 weeks full term? | Yes, full term | Fewest newborn problems in uncomplicated pregnancies (ACOG) | ACOG: the earliest week for a planned birth with no medical reason |
| Is 40 weeks full term? | Yes, full term | Your due date (40+0) falls here | As at 39 weeks |
| Is 41 weeks full term? | No, late term | The week after full term | ACOG: testing, and possibly induction, may be recommended |
| Is 42 weeks full term? | No, postterm | 42 weeks 0 days and beyond | NHS: past 42 weeks, more monitoring if you decline induction |
Earlier weeks, such as 32, are preterm too (ACOG). Not sure of your week? Enter your last period or IVF transfer date to see your weeks and days.
How Many Weeks Is Full Term, and Why Did It Change?
Full term lasts two weeks, 39 weeks 0 days through 40 weeks 6 days: from 7 days before your due date to 6 days after it. A full term pregnancy is one that ends in that window.
On average, pregnancy lasts 40 weeks, or 280 days, from the first day of your last period (ACOG). That makes your due date 40 weeks 0 days, and our guide to Naegele's rule shows the calculation. The count assumes ovulation on day 14 of a 28-day cycle (ACOG Committee Opinion 700), so it starts about two weeks before you conceived.
Why "term" was split into four
Before 2013, the five weeks from 3 weeks before the due date to 2 weeks after it all counted as "term," on the expectation that babies born in that window did equally well. Researchers found that newborn outcomes, breathing problems in particular, varied across those weeks, and that problems were least frequent in uncomplicated pregnancies delivered at 39 weeks 0 days to 40 weeks 6 days (ACOG, 2013). A work group with members from NICHD, ACOG and SMFM proposed the four labels.
The NICHD puts it in plain terms: your baby's lungs, liver and brain "go through a crucial period of growth between 37 weeks and 39 weeks of pregnancy" (NICHD).
Your week depends on your due date
A due date is an estimate. About half of women recall the first day of their last period correctly, ACOG notes. A first-trimester ultrasound, up to 13 weeks 6 days, is the most accurate method to establish or confirm how far along you are, with an accuracy of plus or minus 5 to 7 days (Committee Opinion 700). Once your provider settles on a due date, ACOG reserves later changes for rare circumstances, so count your weeks from theirs.
For a made-up due date of May 20, 2027:
| Category | Starts | Ends |
|---|---|---|
| Early term | April 29, 2027 (37+0) | May 12, 2027 |
| Full term | May 13, 2027 (39+0) | May 26, 2027 |
| Late term | May 27, 2027 (41+0) | June 2, 2027 |
| Postterm | June 3, 2027 (42+0) | No end date |
Is It Safe to Deliver at 37 Weeks?
ACOG answers in two parts, depending on whether there's a medical reason for an earlier birth. These two parts are general guidance, and your OB or midwife can say what fits your pregnancy.
Without a medical reason, ACOG and SMFM say a delivery, including a cesarean, an induction or cervical ripening, should not happen before 39 weeks 0 days (Committee Opinion 765, 2019). Newborns delivered at 37 or 38 weeks have a higher risk of adverse outcomes than those delivered at 39 weeks.
In one large US study ACOG cites, 17.8% of babies delivered at 37 weeks without a medical reason were admitted to the NICU, against 8% at 38 weeks and 4.6% at 39 weeks or later. ACOG notes that NICU admission depends on many factors, and that this opinion is under revision.
With a medical or obstetric indication for an earlier birth, ACOG says deferring delivery to the 39th week "is not recommended" (Committee Opinion 831, 2021). The timing weighs the risks of an earlier birth against the risks of continuing the pregnancy, and ACOG says it should be individualized. ACOG's examples of medical reasons include preeclampsia, placenta previa, fetal growth restriction and multiple gestations (Committee Opinion 765). Expecting twins or more? Ask your provider which week they suggest, and why.
The 39-week guidance covers births started on purpose. If you think labor is starting on its own, our guides to early labor contractions and the 5-1-1 rule cover what to watch for.
Questions for your OB or midwife if a date before 39 weeks comes up:
- Which week is my pregnancy in, and how was my due date set?
- What is the medical reason for a date before 39 weeks?
- What happens for me and for the baby if we wait?
- Could the baby need extra care after the birth, and is it available where I'm delivering?
Is It Safe to Deliver at 36 Weeks?
36 weeks is late preterm, the last week before early term. The 39-week guidance applies here too: a planned birth needs a medical reason, and the condition sets the timing (Committee Opinion 831).
For an expected late-preterm birth, ACOG recommends a single course of the steroid betamethasone within 7 days of delivery for select patients who haven't had one, without delaying a medically indicated birth to give it. Ask your OB whether this applies to you.
Is It Safe to Deliver at 35 Weeks?
35 weeks is late preterm too, with the same guidance. If labor seems to be starting before 37 weeks, ACOG says not to wait: call your ob-gyn's office right away or go to the hospital. Signs ACOG lists include regular or frequent contractions or tightening (often painless), a constant low, dull backache, pelvic pressure, a change in vaginal discharge and your water breaking.
What Late Term and Postterm Mean
A late term pregnancy has reached 41 weeks 0 days through 41 weeks 6 days, and postterm starts at 42 weeks 0 days (ACOG). At 41 weeks, ACOG says your ob-gyn may recommend testing and may recommend induction, and in the UK the NHS offers induction if labor hasn't started by 41 weeks. Our guide to what happens if you go past your due date covers the tests and choices.
How Many Months Is 37 Weeks?
37 weeks is 259 days from the first day of your last period, about 8½ calendar months (259 ÷ 30.44). A chart that counts four-week months says a little over 9. Our weeks-to-months chart shows both, and 37 weeks pregnant and 39 weeks pregnant cover those weeks themselves.
Find your week. Our due date calculator shows your estimated due date, how many weeks and days pregnant you are, your trimester and the days left, starting from your last period, an ovulation or conception date, or an IVF transfer date. It doesn't take an ultrasound date, so if a scan changed your due date, go by your provider's. Open the due date calculator.
Frequently Asked Questions
Is 37 weeks full term?
No. Since 2013, ACOG has called 37 weeks 0 days through 38 weeks 6 days early term. Full term is 39 weeks 0 days through 40 weeks 6 days. A due date is an estimate, so ask your provider which week your pregnancy is in.
Is 38 weeks full term?
No. 38 weeks is the second and last week of early term. Full term starts the next day, at 39 weeks 0 days (ACOG).
Is 36 weeks full term?
No. 36 weeks is late preterm, which ACOG defines as 34 weeks 0 days through 36 weeks 6 days. Any birth before 37 weeks is preterm.
How many weeks is full term?
Full term is 39 weeks 0 days through 40 weeks 6 days, a two-week window that starts 7 days before your due date. Pregnancy averages 40 weeks, or 280 days, from the first day of your last period.
Is it safe to deliver at 37 weeks?
ACOG advises against a planned birth before 39 weeks without a medical reason, because babies born at 37 or 38 weeks have a higher risk of problems than those born at 39. With a medical reason, an earlier birth may be advised. Ask your OB or midwife why.
Is 39 weeks full term?
Yes. Full term begins at 39 weeks 0 days and runs through 40 weeks 6 days. ACOG says a planned birth without a medical reason should not happen before 39 weeks 0 days.
What is the difference between early term and full term?
Early term is 37 weeks 0 days through 38 weeks 6 days; full term is 39 weeks 0 days through 40 weeks 6 days. ACOG split them because newborn outcomes, breathing problems in particular, differ across those weeks.
This article is for information only and does not replace medical advice from your OB or midwife.
How This Guide Was Made
The Babysential Team wrote this guide from the sources below, checked on October 11, 2026, with AI-assisted drafting. The example dates are made up and were computed by script.
Sources
- Definition of Term Pregnancy, Committee Opinion No. 579. ACOG and SMFM, 2013, reaffirmed 2025
- Avoidance of Nonmedically Indicated Early-Term Deliveries and Associated Neonatal Morbidities, Committee Opinion No. 765. ACOG and SMFM, 2019
- Medically Indicated Late-Preterm and Early-Term Deliveries, Committee Opinion No. 831. ACOG and SMFM, 2021
- Methods for Estimating the Due Date, Committee Opinion No. 700. ACOG, AIUM and SMFM, 2017, reaffirmed 2025
- Preterm Labor and Birth. ACOG, last reviewed 2026
- When Pregnancy Goes Past Your Due Date. ACOG, last reviewed 2026
- Know Your Terms: Moms-to-be. NICHD, last reviewed 2022
- Preterm Birth. CDC, 2024
- Inducing labour. NHS, 2023
