How Many Weeks Is A Full-Term Pregnancy? | Full Term Timing

“Full term” sounds like one neat finish line. In real care, it’s a week-and-day range with official cutoffs. Those cutoffs shape how due dates are set, how births get labeled in records, and how clinicians talk about timing.

Below you’ll get the definition, the math behind week counting, and a few practical ways to use the numbers without getting stuck in calculator loops.

How Pregnancy Weeks Are Counted In Clinics

Most prenatal charts count from day 1 of your last menstrual period (LMP). That is earlier than conception for many people. LMP is used because it’s often a date people can recall, while ovulation and implantation can vary and may not be obvious.

So “40 weeks pregnant” usually means 40 weeks since LMP, not 40 weeks since conception. In a textbook 28-day cycle, conception often lands near week 2 on that calendar.

Gestational Age Vs. Conception Timing

Gestational age is the week count used in prenatal care. It starts at LMP. Conception timing starts at fertilization. The two numbers often differ by about two weeks, yet care plans, screening windows, and “term” labels use gestational age.

Why “Weeks And Days” Shows Up Throughout Your Chart

Many thresholds are written as week/day ranges, like 39 0/7 or 40 6/7. It’s just a precise way to write “weeks completed” plus “days into the next week.”

How Many Weeks Is A Full-Term Pregnancy? Facts With Clear Cutoffs

In modern obstetrics, “term” is split into bands. A pregnancy that reaches 37 weeks is no longer labeled “preterm,” yet 37 weeks is not “full term.” The full-term band starts at 39 weeks.

The American College of Obstetricians and Gynecologists lays out the official week cutoffs in its Definition of Term Pregnancy.

What “Full Term” Covers

“Full term” runs from 39 weeks 0 days through 40 weeks 6 days. Your due date at 40 weeks 0 days sits inside that range, not at the far edge of it.

Where The 40-Week Due Date Comes From

Many clinics start with a due date set at 40 weeks from LMP, which equals 280 days. Johns Hopkins Medicine explains this common approach when calculating a due date.

That date is an estimate. It’s still useful because it anchors your week count, and many prenatal milestones are timed off that anchor.

Term Labels That Sound Similar But Mean Different Weeks

People often use “term” as a catch-all for “37 weeks or more.” The medical labels are tighter than that. Here are the core bands you’ll see in charts and discharge paperwork.

Early Term: 37 Weeks 0 Days Through 38 Weeks 6 Days

Early term is “term,” yet it’s earlier than the full-term band. If a birth is scheduled before 39 weeks, the record may show an early-term gestational age at birth.

Full Term: 39 Weeks 0 Days Through 40 Weeks 6 Days

This is the full-term window. It includes the due date itself and almost a full week after it.

Late Term: 41 Weeks 0 Days Through 41 Weeks 6 Days

Late term means you’re past the due date by about a week. Monitoring and timing talks often pick up in this band, based on how pregnancy is going.

Postterm: 42 Weeks 0 Days And Beyond

Past 42 weeks is labeled postterm. MedlinePlus describes this cutoff and the broader week ranges on its Gestational age page.

Why The Definition Of “Term” Was Split Into Bands

Years ago, many people heard “term” and thought “37 weeks and up.” Clinicians noticed that the week within that span still matters for newborn breathing, feeding, and temperature control. The ACOG term bands were created to put clearer language on those week differences, so records and timing talks aren’t fuzzy.

This matters most when birth is being planned. If a C-section or induction is being scheduled for a non-medical reason, many practices aim for 39 weeks or later, since 39 weeks sits inside the full-term window. When timing is being considered for a medical reason, your team weighs the reason for birth against the week and day count.

What This Means For Your Plans

If you’re trying to line up childcare, travel, or work leave, think in ranges, not one date. Full term covers almost two full weeks. Early term is still term, yet it sits before 39 weeks. Late term starts at 41 weeks.

That range thinking also helps when someone asks, “When will the baby come?” A more honest answer is, “Somewhere around the due date,” with room on both sides.

How To Read Week Notation Like 39 4/7

Charts sometimes write weeks as 39 4/7. That means 39 weeks and 4 days. A simple way to translate it is to treat the fraction as “days out of seven.” If you see 38 0/7, that’s exactly 38 weeks.

Term Week Bands At A Glance

If you want a quick reference you can save, this table puts the week ranges next to what they usually signal in planning and records.

Week range (gestational)	Label used in records	What it usually signals
Less than 37w0d	Preterm	Birth before “term” week cutoffs
37w0d–38w6d	Early term	Term birth, yet earlier than full term
39w0d–40w6d	Full term	Full-term window; includes 40w0d
41w0d–41w6d	Late term	Past the due date by about a week
42w0d and up	Postterm	Past 42 weeks; timing plans tend to tighten
40w0d	Estimated due date	Calendar marker used to anchor week counts
39w0d	Full-term start	Threshold many clinicians use for planned birth timing
38w0d	Common “almost there” point	Many people start finishing logistics and packing

Why Your Due Date Can Change After An Ultrasound

It can be unsettling when an app says 10 weeks and an ultrasound reads 9 weeks 2 days. A shift like that is often a recalibration, not a scolding.

Early ultrasounds date pregnancy by measuring fetal size. If that measurement points to a different gestational age than LMP suggests, clinicians may adjust the due date to match the scan, since early growth patterns are more uniform than later ones.

Common Reasons Your App And Your Chart Don’t Match

• Cycle length differs from 28 days. Later ovulation can make LMP dating look “ahead.”
• Irregular periods. LMP can be a weak anchor when cycles swing.
• Bleeding confusion. Spotting can be mistaken for a period.
• IVF or tracked ovulation. Known dates can reset the timeline, then get converted to standard gestational weeks.

Once a due date is set, the simplest move is to use the gestational age listed at visits as your “official” count. It lines up with test timing and clinician notes.

How To Track Your Weeks Without A Calculator Spiral

You don’t need five apps. Pick one method and stick with it.

Count From LMP

1. Write down the first day of your last menstrual period.
2. Count forward in blocks of 7 days.
3. Add leftover days to get the weeks-and-days format, like 24w3d.

Count Back From Your Due Date

Your due date is 40w0d. Each day before it is one day less. Ten days before it is 38w4d.

Use Your Visit Note Week Count

This is the least stressful option. It’s the number your care team uses for scheduling tests and interpreting results.

What People Mean When They Say “Past Due”

“Past due” usually means you’re beyond 40w0d. Many pregnancies still end between 37 and 42 weeks. MedlinePlus notes that range and explains post-term timing in its guidance on when you pass your due date.

When you cross 41 weeks, you enter the late-term band. That’s when many practices start closer monitoring and talk more about timing options, based on your history and how things look at checks.

Dating Tools Compared: What Each One Does Well

If your due date shifted once and then stayed locked, that’s common. The earlier the scan, the more consistent dating tends to be.

Dating method	Best timing	Why the date may shift
LMP (last menstrual period)	Regular cycles and clear recall	Ovulation later than the “textbook” day
First-trimester ultrasound	Early scan	Measurement differs from LMP estimate
IVF dating	Known fertilization timing	Converted to standard gestational weeks
Second-trimester ultrasound	No early scan available	Wider normal size range can blur dating
Ovulation tracking	Consistent LH testing	Implantation timing still varies
Physical exam dating	Early visits	Natural size variation makes this rough

Red Flags That Should Not Wait For The Next Appointment

Most questions can wait for a phone call in office hours. A few should be treated as urgent. If you have heavy bleeding, severe belly pain, fluid that keeps leaking, fainting, trouble breathing, or a severe headache with vision changes, seek urgent medical care right away.

If you feel your baby’s movements have dropped sharply after you’ve been feeling regular movement, contact your maternity unit or clinician the same day.

Practical Ways To Plan Around The Full-Term Window

Knowing that full term starts at 39 weeks helps you set realistic plans without treating the due date like a deadline.

Leave, Travel, And Visitors

If you can choose, aiming big plans to wrap up by 38 weeks keeps things calmer. For visitors traveling in, the 38 to 40 week range often covers early term through full term.

Get-Bag Timing

A simple rule is to have your bag ready by 36 to 37 weeks. Then you’re covered if labor starts sooner than expected.

Takeaway You Can Use Today

A full-term pregnancy is defined as 39w0d through 40w6d. The due date at 40w0d is the middle of that band, not the end. Use the week-and-day count in your chart for tracking, and use term bands as your planning map.