The term categories
“Term” used to mean anything from 37 to 42 weeks. Because outcomes differ within that range, the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine introduced more precise labels in 2013:
| Category | Gestational age |
|---|---|
| Preterm | Before 37 weeks 0 days |
| Early term | 37 weeks 0 days – 38 weeks 6 days |
| Full term | 39 weeks 0 days – 40 weeks 6 days |
| Late term | 41 weeks 0 days – 41 weeks 6 days |
| Post-term | 42 weeks 0 days and beyond |
The Pregnancy Term Calculator converts each of these into your dates and tells you which category you are in today.
Why the categories matter
The extra weeks before full term are a time of important development, especially for the brain, lungs and liver. That is why planned births without a medical reason are generally not scheduled before 39 weeks. After 41 weeks, the placenta may work less efficiently for some pregnancies, so monitoring increases and induction is commonly discussed.
Preterm birth
Preterm birth is further divided by how early it happens — late preterm (34–36 weeks), moderately preterm (32–33 weeks), very preterm (28–31 weeks) and extremely preterm (before 28 weeks). If you notice regular tightening, fluid leaking, bleeding or pelvic pressure before 37 weeks, contact your maternity unit straight away.
For your full week-by-week timeline, see the Pregnancy Timeline; for a countdown, the Days Until Due Date Calculator.