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A baby born before 37 weeks gestation is considered premature. All premature babies are small and may require extra monitoring in the Neonatal Intensive Care Unit (NICU). Premature babies may have trouble breathing, maintaining their body temperature, and/or eating on their own. Those most at risk of medical complications are babies born very early, while babies born close to term may not need much additional assistance at all. Week by week, preemies gain strength and reach milestones toward life beyond the NICU. Let’s take a look at the complications and care premature babies may require week by week.
Milestones for Preemies Week by Week
Each day in utero helps a baby’s transition to life outside the womb go more smoothly. Fetal organ development and weight gain is best during pregnancy, but with excellent care from modern medical advances most premature babies catch up to their full-term peers by 2-3 years of age.
23-24 weeks is usually considered the age of viability for newborns. This means that at this stage of pregnancy, there is a chance (roughly 50%) that a baby will survive with complex medical assistance. In some rare and remarkable cases, babies born even earlier than 23-24 weeks have survived and thrived.
Babies born at 23-24 weeks are called “micro-preemies”. They typically weigh about one pound and measure about 8 inches from crown to rump. Micro-preemies will be covered in a fine hair called lanugo and will have thin, delicate skin. They may be born with their eyes closed, but they are able to hear if there is no hearing loss present.
Micro-preemies will require intensive and long-term support to breathe, eat, and maintain body temperature. They will have breathing tubes, ventilators, feeding tubes, IV lines, and several monitors attached to monitor their heart rate, respiration, oxygen levels, and blood sugar. They require 24/7 NICU care for several months, typically until around their original due date or longer.
Babies born at 25-26 weeks weigh roughly 1.5-2 pounds, and average 9 inches in length from head to bottom. Still referred to as micro-preemies, these babies require many weeks of NICU care and may face long term or lifelong health challenges.
However, these little fighters will meet key milestones in weeks 25-26. The first is developing alveoli, the tiny air sacs in the lungs that allow gas exchange of oxygen and carbon dioxide, which happens around 26 weeks’ gestation. While they will still need help breathing on their own, this is a step toward graduating to a CPAP machine instead of a breathing tube and ventilator.
In addition, micro-preemies will develop a startle reflex, a normal neurological response to loud noises or movement.
Now called “very premature babies,” babies born in weeks 27-28 have a 90-95% chance of survival beyond the NICU. Babies born at this stage weigh about 2.5 pounds and measure 16 inches long from head to toe.
Very premature babies still need help to breathe, but they may not require a ventilator. 27-28 weekers are still too young to feed orally and will have a feeding tube placed. Babies at this stage are undergoing rapid eye development, and are also beginning to develop more coordinated sleep/wake cycles with periods of REM sleep.
By 29-30 weeks, babies weigh about 3 pounds and measure about 17 inches in length. While still needing a great deal of medical support, babies born at this stage have much more developed organs than micro-preemies. They will be better able to control their body temperature, and may not require ventilation. Some 29-30 weekers are able to breathe room air within days or weeks.
At 29-30 weeks, babies are beginning to shed their lanugo. While they still won’t be able to feed by mouth, they may be able to begin sucking on a pacifier to strengthen and coordinate their oral muscles in preparation for breast or bottle feeding.
A baby born at 31-32 weeks will typically weigh between 3.5-4 pounds and will measure 18-19 inches long. Babies born at 31-32 weeks will still require NICU care, but they may not have any long term health challenges or developmental delays due to prematurity.
By 31-32 weeks, babies are putting on more body weight and may not need much help from an incubator to maintain their body temperature. They may need a feeding tube for only a short time. Depending on the NICU facility’s policies, they may attempt breast or bottle feedings at this age, or they may wait until closer to 34 weeks. Babies born at 31-32 weeks may be ready to go home by 35-37 weeks gestation.
Babies born at 33-34 weeks have graduated to “moderate prematurity.” Babies this age weigh between 4 and 5 pounds on average and can measure up to 20 inches long. Babies born between 33-34 weeks are nearly fully developed, typically needing the most help with coordinating breathing and sucking. They may not need help with breathing, or they may require a nasal cannula to deliver oxygen. Their immune systems are also still immature.
At 33-34 weeks, babies are learning to coordinate their suck-swallow-breathe reflex. They can attempt bottle or breast feeds, but will need to be monitored closely to observe their oxygen levels. Very occasionally, a 34 week old baby will be able to be discharged shortly after birth, with only NICU observation. More commonly, babies at this stage will need help for a few days or weeks to control jaundice and gain strength to eat and maintain body temperature independently.
Now referred to as “late preterm,” babies born at 35-36 weeks usually need mostly monitoring to ensure they are transitioning well. Averaging 5.6-6 pounds and up to 20 inches in length, these babies may only require a few days to a couple of weeks in the NICU. Some babies are able to be discharged with their mothers shortly after birth, skipping the NICU entirely.
By 35-36 weeks, most babies are able to breast or bottle feed, but they may need time to build their strength to finish a whole feeding. They’re less alert than full-term babies and may also need phototherapy for jaundice. In the NICU, their blood sugar will be monitored as well as their vital signs. They may also need to pass a car seat test before discharge to ensure they maintain adequate oxygen levels while using a car seat.
Celebrate Every Milestone
Having a premature baby is hard, with many intense emotions and a steep learning curve. Learning what to expect for preemies week by week is helpful to know what may lie ahead. However, remember that each baby is unique and will develop at their own individual rate. Take it day by day, week by week, and celebrate every milestone along the way.