Early term, full term, late term: what the definitions mean

Most people think of a pregnancy as "due" on a single date, but medical care treats the end of pregnancy as a range, with specific names for each part of it. Knowing what early term, full term, and late term mean makes it easier to follow conversations with your care team as your due date approaches.

Why definitions changed

For many years, any birth from 37 to 42 weeks was simply called "term". Research showed that outcomes for babies born at 37 or 38 weeks were measurably different from those born at 39 or 40 weeks. In 2013, the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine introduced more specific categories, which are now widely used.

The categories

• Preterm: born before 37 weeks and 0 days.
• 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.
• Post-term: 42 weeks 0 days and beyond.

Preterm is often divided further. Births from 34 weeks through 36 weeks 6 days are called late preterm, and earlier births have additional categories.

Why the extra weeks matter

Important development continues right up to the end of pregnancy. The brain, lungs, and liver are still maturing in the final weeks, and babies born at 39 weeks or later are generally less likely to need breathing support or have feeding difficulties than those born a couple of weeks earlier. That's one reason guidelines discourage scheduling elective deliveries before 39 weeks unless there's a medical reason.

Going well past the due date also carries risks, which is why providers monitor more closely after 40 or 41 weeks and may discuss induction. The specific plan depends on individual circumstances and your provider's assessment.

How accurate dating affects this

Because these categories are defined in weeks and days, the due date they're based on matters. That's why providers put weight on early dating, often confirmed with a first-trimester ultrasound. A due date that's off by a week could shift a baby from one category to another on paper.

What to expect near your due date

Only a small percentage of babies are born on their exact due date, so it's worth thinking of it as the middle of a window. As you approach 37 weeks, it can help to have your bag packed, transport planned, and your provider's instructions for when to call or come in close at hand. The contraction timer can help track labor when it starts, and continuing to pay attention to your baby's movements is important right up until birth.

Check where you are

The pregnancy week calculator shows your exact gestational age in weeks and days, and the due date calculator shows your estimated due date. If your provider has given you a date, use theirs; it reflects your specific care and any ultrasound dating.