What Is Considered a Full-Term Pregnancy—and Why Does It Matter?
You know that having a full-term pregnancy is the goal, but you might be confused about what this actually means. The definition of a full-term pregnancy has evolved throughout the years, and this has made the question a bit more complicated. So exactly what is a full-term pregnancy? In short, it’s one that reaches the 39-week mark—but there’s more to it than that. Here, we break it all down.
Most of us think of pregnancy as a 40-week journey, since baby’s due date is set 40 weeks from your last menstrual period. Of course, babies don’t have an eviction-time alarm clock, and pregnancy can last beyond your due date—or it can be cut short by an early arrival. So at what point is your pregnancy considered full-term?
According to the American College of Obstetricians and Gynecologists (ACOG), about a decade ago, the period stretching from three weeks before your due date to two weeks after your due date (37 to 42 weeks) was simply considered a pregnancy that went to “term.” This was a bit misleading and open to interpretation though; there’s a wide range of outcomes that can occur between the 37- and 42-week marks. To that end, in 2013, ACOG replaced that one-word blanket phrase with more specific definitions for “early-term,” “full-term,” “late-term” and “postterm” pregnancies. Here’s a breakdown of the timing for each:
- Preterm: Before 37 weeks (also known as premature)
- Early-term: 37 through 38 weeks, 6 days
- Full-term: 39 through 40 weeks, 6 days
- Late-term 41 through 41 weeks, 6 days
- Postterm: 42 weeks and beyond
These more specific time frames help shape a general understanding of the later days of pregnancy, since outcomes for babies born in the five week stretch between what’s now considered preterm and postterm vary greatly, explains Victoria Mui, MD, assistant professor of clinical obstetrics and gynecology at the University of Pennsylvania Perelman School of Medicine. For example, early-term babies are more likely to need help breathing and a stay in the NICU than those born full-term.
Some parts of your pregnancy can’t be controlled, including when your body decides to go into labor. Of course, doctors and midwives typically prefer that a pregnancy reaches full-term status, whenever possible. “The risk for adverse outcomes, including NICU admission, respiratory difficulties, hospitalization and decreased childhood cognitive performance, is higher in preterm and early-term babies, compared to full-term deliveries,” explains Kirsten Phillips, MD, an ob-gyn in Grand Rapids, Michigan.
The last few weeks of gestation are critical for baby’s health and development. “This is an important time for baby to fully develop their lungs, brain and liver, in particular,” says Matthew Carroll, MD, assistant professor of obstetrics and gynecology at Baylor College of Medicine in Houston. “This allows them to better maintain glucose levels, temperature and breathe without assistance.”
Lung development during this window of time is usually the biggest concern, adds Phillips, noting that many early-term babies experience respiratory difficulties. Furthermore, some potential consequences of a premature birth can continue into early childhood.
The fact is, not every baby will be born full-term. And there are a few potential risks associated with a delivery that happens before the 39-week mark. Here are some common issues faced among premature and early-term babies:
- NICU admission. They’re more likely to need a stay in the NICU, says Jian Jenny Tang, MD, assistant professor of obstetrics, gynecology and reproductive science at the Icahn School of Medicine at Mount Sinai. One large study found that admission to the NICU was necessary for 17.8 percent of infants delivered at 37 weeks, 8 percent of those delivered at 38 weeks and 4.6 percent born at 39 weeks.
- Health concerns. “If they can’t breathe for themselves, they may need to be intubated and put on a ventilator,” says Alexander Lin, MD, an ob-gyn at Northwestern Medicine Palos Hospital. They may also require a feeding tube. Babies born early often have trouble maintaining their body temperature, so they might be placed under a warmer, she adds.
- Long-term health issues. There’s also some data to suggest that babies born early “may have long-term development and health problems later in life,” Mui says. According to Mayo Clinic, potential complications of preterm birth include vision and hearing problems, dental issues, psychological and behavioral problems and chronic health concerns, such as asthma.
- Cognitive abilities. Multiple studies have found an increase in cognitive scores for children born at full-term versus those born early-term (between 37 and 38 weeks), regardless of the age of testing and method used.
It’s important to remember that a lot of possible complications depend on the specific newborn. “Some babies need more assistance than others,” Phillips says. What’s more, potential outcomes for baby improve with every week of gestation before a pregnancy reaches the full-term mark, per ACOG.
For whatever reason, some babies staunchly stay in utero past their due date. While it’s true that due dates have some built-in wiggle room, pregnancies that go beyond the 41-week mark are more likely to experience complications. Here are some potential risks:
- Placental deterioration. There’s a greater risk that the placenta will stop functioning at peak capacity. This can lead to fetal distress, notes Phillips.
- Postpartum hemorrhage. ACOG notes that there’s a higher risk of postpartum hemorrhage and infection with postterm pregnancies.
- Decreased amniotic fluid. According to ACOG, this can cause the umbilical cord to pinch and restrict the flow of oxygen to baby.
- More medical interventions. There’s a higher chance of needing a c-section or forceps–assisted delivery use with postterm births, per ACOG.
- Meconium. There is also a higher risk of baby breathing in meconium—baby’s first poop—when they take their first breath.
- High birth weight. Late- and postterm newborn may [weigh more than other babies](, which can increase the risk of a birth injury, Phillips says. Furthermore, there’s a higher risk of birth injury with a large baby, per the University of Rochester Medical Center.
- Fetal demise. “Late- and postterm pregnancies carry a higher risk of sudden fetal demise before delivery,” says Phillips.
All of this sounds alarming. But rest assured that, if your due date has come and gone, your doctor or midwife will monitor you closely. They may even talk about inducing you before you become postterm, Mui says. “We typically recommend an induction after 41 weeks because this decreases the risk of c-section, admission to the NICU and stillbirth,” she adds, noting that her medical practice recommends tests to monitor baby’s health if a pregnancy continues to the 42-week mark. “There’s technically no ‘maximum’ gestational age, but the data shows us that the longer a baby stays inside the womb after 41 weeks, the higher the risks of negative outcomes,” says Mui. To this end, many doctors won’t let you go beyond 41 weeks—and almost all will induce by 42 weeks.
You want to have a healthy, happy full-term pregnancy. Hopefully, baby will make their big debut sometime within that 39- to 41-week window. But remember: All pregnancies—and births—are unique. Your little one may come early, or they may take their sweet time. Address any concerns with your OB or midwife, and try not to stress too much about the exact timeline.
Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.
Plus, more from The Bump:
Matthew Carroll, MD, is an ob-gyn and assistant professor of obstetrics and gynecology at Baylor College of Medicine in Houston. He received his medical degree from the Mount Sinai School of Medicine in New York.
Alexander Lin, MD, is an ob-gyn at Northwestern Medicine Palos Hospital. He received his medical degree from the University of Michigan Medical School.
Victoria Mui, MD, is an ob-gyn and assistant professor of clinical obstetrics and gynecology at the University of Pennsylvania Perelman School of Medicine. She earned her medical degree from Jefferson Medical College in Philadelphia.
Kirsten Phillips, MD, is an ob-gyn with SHMG Obstetrics and Gynecology in Grand Rapids, Michigan. She received her medical degree at the University of Toledo.
Jian Jenny Tang, MD, is an ob-gyn and assistant professor of obstetrics, gynecology and reproductive science at the Icahn School of Medicine at Mount Sinai. She earned her medical degree from the University of Wisconsin.
American College of Obstetricians and Gynecologists, Definition of Term Pregnancy, November 2013
American College of Obstetricians and Gynecologists, Avoidance of Nonmedically Indicated Early-Term Deliveries and Associated Neonatal Morbidities, February 2019
Mayo Clinic, Premature Birth, February 2023
Wellcome Open Research, Long term cognitive outcomes of early term (37-38 weeks) and late preterm (34-36 weeks) births: A systematic review, October 2017
American College of Obstetricians and Gynecologists, When Pregnancy Goes Past Your Due Date, November 2021
University of Rochester Medical Center, Post-Term Pregnancy, 2023
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