For many years, a baby was defined as being born at “term” if it was born between 37 weeks 0 days and 41 weeks 6 days. Anything before that 5-week period was considered “preterm,” and anything after those five weeks was “post-term. Over time, though, research began to show that health problems were more common at certain points during this 5-week “term” period. In particular, newborns are more likely to die (although the overall risk was still very low) if they are born before 39 weeks, or after 41 weeks. The chance of a newborn having problems is lowest if he or she is born between 39 weeks and 0 days and 40 weeks and 6 days (Spong 2013). In 2012, a group of experts came together to define “term” pregnancy. Based on their review of the research evidence, they broke the 5-week term period into separate groups (Spong 2013)
- “Early term” babies are born between 37 weeks 0 days and 38 weeks 6 days
- “Full term” babies are born between 39 weeks 0 days and 40 weeks 6 days.
- “Late term” babies are born between 41 weeks 0 days and 41 weeks 6 days
- “Post term” babies are born at 42 weeks and 0 days or later