A baby is considered full term at 39 to 40 weeks of pregnancy; specifically, from 39 weeks 0 days to 40 weeks 6 days.

Quick Scoop

  • Early term: 37 weeks 0 days to 38 weeks 6 days – not premature, but a bit earlier than ideal.
  • Full term (the “sweet spot”): 39 weeks 0 days to 40 weeks 6 days – best overall outcomes for most babies.
  • Late term: 41 weeks 0 days to 41 weeks 6 days.
  • Postterm: 42 weeks and beyond.

Doctors narrowed the definition of full term in the last decade because babies born closer to 39–40 weeks tend to have fewer breathing, feeding, and developmental problems than those born a bit earlier in the 37–38 week window.

Why 39 weeks matters

  • By 39 weeks, the baby’s brain, lungs, and liver have had crucial extra time to mature.
  • Staying pregnant (when it’s safe) until at least 39 weeks lowers the risk of NICU care, breathing issues, and some long-term learning and behavior problems.
  • Planned inductions or C‑sections are usually recommended at 39 weeks or later unless there is a medical reason to deliver earlier.

What about 37 or 38 weeks?

  • Many babies born at 37–38 weeks are healthy, but as a group they have slightly higher risks of breathing troubles, feeding difficulties, jaundice, and NICU admission compared with babies born at 39–40 weeks.
  • That’s why you may see messaging like “wait for 39 weeks if you can.”

One more nuance

  • For twins , doctors often consider 37 weeks functionally “full term,” because twin pregnancies rarely go as long as singleton pregnancies.
  • Every pregnancy is unique, so decisions about inducing or waiting past your due date should always be made with your own healthcare provider.

Bottom line: In modern medical guidelines, “full term” means 39–40 weeks of pregnancy, because that timing offers the best balance of safety and readiness for most babies.

Information gathered from public forums or data available on the internet and portrayed here.