This article is professionally consulted by a Pediatric - Neonatal Specialist, Vinmec Nha Trang International Hospital.
Infants born at 37 weeks of gestation are considered early-term infants. Although externally they may resemble full-term infants, early-term newborns face higher risks of health complications. What is the developmental outlook for a baby born at 37 weeks?
1. What Is Full-Term Pregnancy?
A typical pregnancy lasts about 40 weeks (280 days), calculated from the first day of the last menstrual period (LMP) to the expected due date. The due date is estimated based on first-trimester ultrasounds or the LMP.
The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) define a full-term pregnancy as one lasting from 39 weeks 0 days to 40 weeks 6 days. This means a pregnancy can vary by one week before or after the due date. Babies born full-term generally have better health outcomes compared to those born earlier or later.
ACOG and SMFM classify full-term pregnancies into the following categories:
- Early-term: 37 weeks 0 days to 38 weeks 6 days.
- Full-term: 39 weeks 0 days to 40 weeks 6 days.
- Late-term: 41 weeks 0 days to 41 weeks 6 days.
- Post-term: After 42 weeks 0 days.
Previously, pregnancies lasting 37 to 42 weeks were all considered full-term. Earlier evidence suggested that this five-week period was a safe time for most babies to be born. However, in 2013, ACOG and SMFM updated these definitions after research highlighted the importance of each week in the final stages of pregnancy. Many important developments occur in the final weeks of pregnancy. Key organ systems, such as the brain and lungs, continue to develop during the last few weeks.
Studies have shown that infants born between 37 weeks 0 days and 38 weeks 6 days (early-term) face higher health risks compared to those born after 39 weeks. One reason is the incomplete maturity of their organs.
2. Risks for Babies Born at 37 Weeks
Although infants born at 37–38 weeks are classified as full-term, they are considered early-term due to the incomplete maturation of vital organs, particularly the brain and respiratory system. These babies may look similar to full-term infants but are at a higher risk for complications.
The proportion of early-term births has increased over recent years, contributing to a general decline in the average gestational age at birth. In the U.S., the average gestational age dropped from 40 weeks in 1994 to 39 weeks in 2004.
Early-term pregnancies are associated with an increased incidence of conditions such as respiratory distress syndrome, transient tachypnea of the newborn, and the need for mechanical ventilation, as well as a higher risk of neonatal mortality at 37 weeks compared to full-term infants. For this reason, both the Royal College of Obstetricians and Gynaecologists (RCOG) and the American College of Obstetricians and Gynecologists (ACOG) have defined full-term pregnancy as beginning at 39 weeks. This aims to reduce the risk of adverse outcomes in infants born before reaching full-term maturity (39–40 weeks of gestation).
There is limited evidence regarding the prevalence of long-term complications in the early-term group, particularly concerning cognitive function. Infants born at later gestational ages are less likely to require specialized care and education in school settings. Studies indicate that full-term births are associated with better neurodevelopment, supported by evidence from magnetic resonance imaging (MRI).
Researchers have found that early-term infants are at significantly higher risk of adverse outcomes compared to full-term infants. They also discovered that elective cesarean deliveries at this gestational age increase the likelihood of unfavorable outcomes, with the risk of neonatal intensive care unit (NICU) admission rising from 9.7% for vaginal births to 19% for cesarean deliveries. Some issues that 37-week infants may face include:
- Difficulty breastfeeding (poor latch, inability to coordinate sucking and swallowing, sleepless)
- Poor weight gain and susceptibility to diarrhea
- Respiratory problems (transient tachypnea, apnea)
- Hypothermia
- Higher susceptibility to infections
- Jaundice (2% in full-term infants versus 18% in early-term infants)
These infants require more rigorous monitoring as they have twice the risk of sudden infant death syndrome (SIDS). This is due to weaker muscle strength for respiratory support and lower body fat, making them prone to hypoglycemia and hypothermia.
Although early-term infants may appear healthy externally, they exhibit subtle differences from full-term infants. Studies suggest a potential risk for delayed cognitive and emotional development.
In the early days, it is crucial to recognize feeding difficulties in early-term infants and seek help from lactation consultants if breastfeeding. Pumping milk or feeding via tube or intravenous methods may be necessary. The baby's blood sugar and oxygen levels must be closely monitored. After discharge, frequent follow-ups with a pediatrician are essential, and parents should be educated on warning signs and seek medical attention promptly if needed.
3. Care for Infants Born at 37 Weeks
Because infants born at 37 weeks are at risk for complications due to incomplete organ development, they may require treatment in a NICU. However, their NICU admission rate is lower compared to preterm infants. This largely depends on the baby’s birth weight and overall health. Certain maternal factors, such as smoking, alcohol use, or substance abuse, increase the likelihood of preterm delivery and associated health issues in the infant. Babies with respiratory symptoms, such as transient tachypnea, may need temporary respiratory support.
Initial care for early-term infants with low birth weight often begins in the NICU. These infants may have a weaker immune system and a higher risk of illness compared to full-term babies. Breastfeeding provides essential antibodies that can help protect against infections.
Key steps in caring for an early-term infant include: Frequent feeding to promote weight gain; Regular pediatric checkups to monitor growth and developmental milestones; If the infant shows signs of long-term complications, consulting with a pediatric specialist is crucial for optimal treatment and management.
For concerns regarding your baby’s health, visit the Vinmec Healthcare System for timely examination and treatment.
Reference source: ncbi.nlm.nih.gov/
