A delivery at 35 weeks is classified as a late preterm birth. A full-term pregnancy officially begins at 39 weeks of gestation and extends through 40 weeks and six days. Since 35 weeks is before 37 completed weeks, it is considered preterm. While infants born at this stage are physically close to full-term, they are not without certain risks and require specialized attention after delivery. The final weeks of development are highly impactful for the baby’s transition to life outside the womb.
Defining Late Preterm Birth
The medical community uses specific terms to categorize births based on gestational age. A birth at 35 weeks falls squarely within the “late preterm” window, which spans from 34 weeks and zero days through 36 weeks and six days of gestation.
This late preterm category represents the majority of all premature births, often accounting for over 70% of preterm deliveries. Babies born earlier, such as those in the “very preterm” category (under 32 weeks), face substantially higher risks. Although a 35-week infant looks much like a full-term baby, their internal organ systems have not yet completed the final stages of maturation. These few weeks before 37 weeks are significant for the baby’s physiological readiness.
Common Reasons for 35-Week Delivery
Delivery at 35 weeks occurs due to two main reasons: spontaneous onset of labor or a medically indicated decision. Spontaneous causes include premature rupture of membranes (water breaking early) or the onset of contractions without a clear trigger. In many cases of spontaneous preterm labor, the exact cause remains unknown.
Medically indicated deliveries are necessary when continuing the pregnancy poses a greater risk to the mother or the baby than early birth. Severe maternal conditions, such as preeclampsia, often necessitate delivery to protect the mother’s organs. Fetal distress, including poor growth or lack of oxygen, can also lead to an induction or Cesarean section. Placental issues, such as placental abruption where it separates from the uterine wall, are also common reasons for early delivery.
Health Outcomes for the 35-Week Baby
The primary concerns for a 35-week baby stem from the immaturity of several body systems.
Respiratory Issues
The respiratory system is frequently challenged because the lungs may not have produced sufficient quantities of surfactant, which helps keep the air sacs open. This deficiency can result in respiratory distress syndrome (RDS) or transient tachypnea of the newborn (TTN), often requiring supplemental oxygen support. Approximately 8% of infants born at 35 to 36 weeks need oxygen support for at least an hour, a rate nearly three times higher than that of full-term infants.
Thermoregulation and Feeding
Another common challenge is the inability to maintain a stable body temperature, known as thermoregulation instability. Late preterm infants have less subcutaneous fat and a maturing nervous system, making it difficult to regulate temperature efficiently. This vulnerability to hypothermia can quickly drain their energy reserves. Feeding can also be a struggle because the coordinated suck, swallow, and breath reflex often does not fully mature until around 37 weeks. This lack of coordination leads to poor milk intake, slower weight gain, and increased risk of dehydration.
Jaundice
The immature liver may struggle to process bilirubin efficiently, leading to a higher incidence of neonatal jaundice. Jaundice is a yellowing of the skin and eyes that can be managed with phototherapy but requires careful monitoring. These combined issues often result in a longer initial hospital stay compared to a full-term infant.
Post-Delivery Care and Monitoring
Due to the physiological challenges of late preterm infants, a baby born at 35 weeks will undergo intensive monitoring in the hospital. While many will not require the Neonatal Intensive Care Unit (NICU), they are frequently admitted to a Special Care Nursery (SCN) or a specialized transitional care unit. This setting allows for close observation by staff trained to manage common late preterm morbidities.
Monitoring protocols include frequent temperature checks, often hourly, to ensure the baby can maintain warmth without assistance. Blood sugar levels are also routinely checked because immature infants can struggle with hypoglycemia, which can impact brain function. Feeding assessments are performed consistently, requiring infants to feed every three hours to ensure adequate intake and weight gain. Before discharge, the baby must demonstrate successful feeding, stable temperature regulation, and the ability to breathe without distress for an extended period.