A baby born at 37 weeks is not classified as premature. Since 2013, medical organizations have used a more specific system that places 37-week births in the “early term” category, distinguishing them from both preterm births (before 37 weeks) and full-term births (39 to 40 weeks). That said, babies born at 37 weeks do face higher risks than those who make it to 39 weeks, which is why the distinction matters.
How Gestational Age Is Classified
The American College of Obstetricians and Gynecologists replaced the old blanket “term” label with four more precise categories:
- Early term: 37 weeks 0 days through 38 weeks 6 days
- Full term: 39 weeks 0 days through 40 weeks 6 days
- Late term: 41 weeks 0 days through 41 weeks 6 days
- Post-term: 42 weeks 0 days and beyond
Anything before 37 weeks 0 days is considered preterm. So a baby born at exactly 37 weeks lands right at the boundary. They’re technically not premature, but they’re also not fully cooked. This two-week gap between early term and full term turns out to be surprisingly consequential for a newborn’s health.
Why Those Last Two Weeks Matter
Between 37 and 39 weeks, a baby’s lungs, brain, and liver are still undergoing important final development. The lungs in particular are producing surfactant, the substance that keeps air sacs from collapsing. The brain gains roughly a third of its weight during the final weeks of pregnancy. The liver is building up the capacity to process bilirubin, the waste product that causes jaundice when it accumulates.
Research published in JAMA found that infants born at 37 weeks are about three times more likely to develop respiratory distress syndrome compared to those born at 39 to 40 weeks. They’re also roughly 2.5 times more likely to experience transient tachypnea (temporary rapid breathing) and nearly three times more likely to need ventilator support. These aren’t small differences. Babies born at 37 weeks were nearly five times more likely to need surfactant treatment than their 39-week counterparts.
NICU Admission Rates
CDC data from 2023 shows that 7.1% of early-term babies (37 to 38 weeks) are admitted to the NICU, compared to 3.8% of full-term babies (39 to 40 weeks). That means an early-term newborn is roughly twice as likely to need intensive care. Most 37-week babies do fine and go home on a normal schedule, but the odds of complications are meaningfully higher.
Feeding and Jaundice Challenges
Babies born at 37 weeks often have a less coordinated suck-swallow-breathe pattern than full-term infants, which can make breastfeeding harder right from the start. They tire more easily during feeds and may not transfer milk as efficiently. This is compounded by the fact that first-time mothers frequently experience delayed milk production. By some estimates, 33% to 44% of first-time mothers don’t see their full milk supply come in until beyond 72 hours after delivery.
When feeding doesn’t go smoothly, a cascade of problems can follow. Inadequate intake raises the risk of excessive weight loss, dehydration, and low blood sugar. Neonatal low blood sugar affects an estimated 5% to 15% of otherwise healthy newborns, and babies who are feeding poorly are at greater risk. Jaundice is also more common at 37 weeks because the liver is less mature and less efficient at clearing bilirubin from the blood. Pediatricians typically monitor early-term babies more closely in the first few days for exactly these issues.
Staying Warm
Temperature regulation is another area where 37-week babies can struggle. They tend to have less body fat and a higher surface-area-to-body-weight ratio than full-term infants, which means they lose heat faster. Lower gestational age and lower birth weight are both associated with higher rates of hypothermia in newborns. Skin-to-skin contact and careful temperature monitoring in the first hours after birth help offset this, and most 37-week babies regulate their temperature well within a day or two.
When Delivery at 37 Weeks Is Planned
Doctors generally aim for delivery at 39 weeks or later, but several pregnancy complications make earlier delivery the safer choice. ACOG guidelines acknowledge that the risks of continuing a complicated pregnancy sometimes outweigh the risks of an early-term birth. Conditions that may prompt delivery at 37 weeks include preeclampsia and other hypertensive disorders, certain types of fetal growth restriction, gestational diabetes with poor blood sugar control, problems with the placenta, low amniotic fluid, twins or other multiple pregnancies, and premature rupture of membranes.
In these situations, the timing is a careful balancing act. The baby benefits from every additional day in the womb, but the mother or baby may face increasing danger from the underlying complication. When your medical team recommends delivery at 37 weeks, it’s because they’ve weighed both sides and determined that the risks of waiting are greater than the risks of delivering early.
What to Expect With a 37-Week Baby
Most babies born at 37 weeks are healthy and do not need the NICU. They typically weigh between 5.5 and 7 pounds, and many are indistinguishable from full-term newborns. The differences tend to show up in subtle ways: slightly more sleepiness, a little more difficulty latching, a touch more sensitivity to temperature changes. These issues generally resolve within the first week or two.
Your pediatrician will likely want to see your baby within a day or two of discharge rather than the standard three to five days, especially to check weight gain and screen for jaundice. If your baby is feeding well, gaining weight, and maintaining body temperature, the early-term label becomes largely academic. The key is close monitoring in those first few days, when the gap between 37 weeks and 39 weeks is most likely to show itself.