Pregnancy usually lasts for  40 weeks from the  first day of your last menstrual period to your due date. Your due date is when your health care professional thinks you will have your baby. Health care experts considered that babies born between 37 weeks and 42 weeks were equally healthy so they considered 37 weeks full term. However, The  American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM)  recently changed the way they define births that happen after 37 weeks of pregnancy. Full  term pregnancy is now defined as  pregnancy that last between 39 weeks 0 days or 40 weeks 6 days. Full term babies have a higher chance of being  healthy as opposed to babies who are born earlier.

Know these new definitions.

 
Early  term : the baby is born between 37 weeks, 0 days and 38 weeks, 6 days.

Full term : the baby is born between 39 weeks, 0 days and 40 weeks, 6 days.

Late term: the baby is born between 41 weeks, 0 days and 41 weeks, 6 days.

Postterm : baby is born after 42 weeks, 0 days.

Why is 39 weeks now considered full term pregnancy?

 
Full term pregnancy used to be anywhere from 37 to 42 weeks. Health care professionals thought  the 5 week period was safe for most babies to be born. However new research indicates that every  day that the baby remains in utero counts towards the health of the baby. Lots of important things happen during the last few weeks of pregnancy. For example the baby’s lungs and brain are still developing during the last weeks. Having the baby at 39 weeks gives his body the time it needs to grow and develop.

This new definition also prevents births that are scheduled early for non medical reasons.  If you have a healthy pregnancy , it is better to wait for labor to begin on its own.

NOTE 

It is possible to go into labor before 39 weeks.  If you go into labor between 37 and 39 week, doctors will not try to stop labor. This is because most babies are fine around this time. However you should know that it is best to wait until 39 weeks to schedule an induction or c-section.
 
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