NICU Glossary for Parents

If you are reading this from a NICU waiting room or a bedside chair, start with whichever word the team just used and you did not catch. You do not need to learn all of these at once. Nurses and neonatologists expect questions, and asking “what does that word mean?” is one of the most useful things a parent can do.

NICU terms, A to Z

A’s and B’s

Shorthand for apnea and bradycardia: brief pauses in breathing and drops in heart rate that are common in premature babies. Nurses often say a baby “had some A’s and B’s” overnight.

Apnea

A pause in breathing lasting long enough to matter, often 20 seconds or more or shorter if paired with a low heart rate or color change. Common in premature infants and usually outgrown.

Bili lights (phototherapy)

Blue-spectrum lights placed over or around a baby to treat jaundice. The light changes bilirubin in the skin into a form the body can remove, lowering the level in the blood.

Bilirubin

A yellow substance made when the body breaks down red blood cells. High levels cause jaundice; very high untreated levels can harm the brain, which is why bilirubin is watched closely in newborns.

Blood gas

A test measuring oxygen, carbon dioxide, and acid levels (pH) in the blood. An umbilical cord blood gas drawn at birth is one of the most objective records of how a baby tolerated delivery.

Bradycardia (“brady”)

A slower-than-normal heart rate. In newborns and preemies, brief bradycardias often go together with apnea and are tracked closely on the monitor.

CPAP (continuous positive airway pressure)

A gentle form of breathing support that pushes a steady stream of air through small prongs in the nose to keep the baby’s airways and lungs open, without a breathing tube.

Cooling (therapeutic hypothermia)

A treatment for moderate-to-severe HIE in which the baby’s body temperature is lowered for about 72 hours to reduce brain injury. It must begin within six hours of birth to help.

Corrected age

A premature baby’s age counted from the original due date rather than the birth date. Used to judge growth and milestones fairly: a baby born two months early is compared as if two months younger.

De-sat (desaturation)

A drop in the oxygen level in the blood, shown as a falling number on the pulse oximeter. Brief de-sats are common; frequent or deep ones prompt a closer look.

ECMO (extracorporeal membrane oxygenation)

A form of life support that pumps a baby’s blood through a machine to add oxygen and remove carbon dioxide, doing the work of the heart and lungs while they recover. Used in the sickest infants.

Encephalopathy

A general term for abnormal brain function. In newborns, “neonatal encephalopathy” describes a baby who is abnormally sleepy or irritable, has abnormal tone, or has seizures; HIE is one cause.

Endotracheal tube (ET tube)

A breathing tube placed through the mouth or nose into the windpipe so a ventilator can breathe for the baby. “Intubation” is the act of placing it; “extubation” is removing it.

Extubation

Removing a baby’s breathing tube when they can breathe well enough on their own or on gentler support.

Gavage feeding (NG/OG tube)

Feeding through a thin tube passed through the nose (nasogastric) or mouth (orogastric) into the stomach, used when a baby cannot yet coordinate sucking and swallowing safely.

Gestational age

How many weeks along a pregnancy was at birth. Term is 37 weeks or more; before 37 weeks is premature, and the earlier the birth, the more support a baby usually needs.

HIE (hypoxic-ischemic encephalopathy)

A newborn brain injury caused by reduced oxygen and blood flow to the brain around the time of birth. Moderate-to-severe cases are treated with cooling. See our full HIE guide.

Hyperbilirubinemia

The medical term for a high bilirubin level in the blood, the condition behind newborn jaundice that phototherapy and, rarely, exchange transfusion are used to treat.

Intraventricular hemorrhage (IVH)

Bleeding into the fluid-filled spaces (ventricles) of the brain, most common in very premature babies. It is graded I through IV by severity and followed with head ultrasounds.

Intubation

Placing a breathing tube into a baby’s windpipe so a ventilator can support or take over breathing.

Jaundice

The yellow coloring of a newborn’s skin and eyes caused by high bilirubin. Common and usually harmless when treated, but monitored because very high levels can be dangerous.

Kangaroo care

Skin-to-skin holding of a baby against a parent’s bare chest. It helps stabilize a baby’s temperature, heart rate, and breathing and supports bonding and breastfeeding.

Kernicterus

A rare, permanent form of brain damage caused by extremely high, untreated bilirubin. Because it is preventable with timely treatment of jaundice, it is closely guarded against. See our kernicterus guide.

Meconium

A newborn’s first, dark stool. If passed before birth into the amniotic fluid and breathed in, it can cause meconium aspiration syndrome, a breathing problem needing extra support.

NEC (necrotizing enterocolitis)

A serious intestinal illness mostly affecting premature babies, in which part of the bowel becomes inflamed and can be injured. It is watched for carefully and can require surgery.

Neonatologist

A pediatrician with extra training in the care of sick and premature newborns. The neonatologist leads the NICU medical team.

NICU (neonatal intensive care unit)

The hospital unit that cares for premature, sick, or recovering newborns, staffed by neonatologists, specialized nurses, respiratory therapists, and others.

PDA (patent ductus arteriosus)

A blood vessel that normally closes soon after birth but stays open, common in premature babies. Small ones often close on their own; larger ones may need medicine or a procedure.

PICC line

A peripherally inserted central catheter, a long, thin IV threaded into a larger vein, used to give nutrition and medicines over days or weeks without repeated needle sticks.

Pulse oximeter (“pulse ox”)

A painless sensor, usually on a hand or foot, that measures the oxygen level in the blood and the heart rate. Its readings drive many of the numbers and alarms parents hear.

Respiratory distress syndrome (RDS)

A breathing problem in premature babies whose lungs lack enough surfactant to stay open. Treated with surfactant and breathing support such as CPAP or a ventilator.

ROP (retinopathy of prematurity)

An eye condition in which blood vessels in the retina grow abnormally in premature babies. It is screened for with eye exams and, when advanced, treated to protect vision.

Sepsis

A serious body-wide response to infection. Newborns are screened and often started on antibiotics quickly when sepsis is suspected, because it can worsen fast.

Surfactant

A soapy substance that keeps the tiny air sacs in the lungs open. Premature babies often lack it and may be given surfactant directly into the lungs to help them breathe.

TPN (total parenteral nutrition)

Complete nutrition (sugars, proteins, fats, vitamins, and minerals) given directly into a vein when a baby cannot yet be fed enough by mouth or tube.

Term / preterm

“Term” means born at 37 weeks of pregnancy or later; “preterm” (premature) means born before 37 weeks. “Late preterm” is 34 to 36 weeks; “extremely preterm” is before 28 weeks.

Umbilical line (UAC/UVC)

A catheter placed into a blood vessel in the umbilical stump, arterial (UAC) or venous (UVC), used in the first days to give fluids and medicines and to draw blood without needle sticks.

Ventilator

A machine that breathes for a baby or supports their breathing through a breathing tube, delivering set amounts of air, oxygen, and pressure.

Vital signs

The core measurements the monitor tracks continuously: heart rate, breathing rate, oxygen saturation, blood pressure, and temperature.

Where to go deeper

Several of the terms above describe conditions we cover in full, parent-friendly detail:

• Hypoxic-ischemic encephalopathy (HIE): how oxygen deprivation at birth is diagnosed, graded, and treated with cooling.
• Kernicterus and newborn jaundice: how high bilirubin is monitored, why kernicterus is preventable, and what the warning signs are.
• Cerebral palsy: what it is, how it relates to birth injury, and what the first years look like.
• The Apgar score, explained: the first numbers assigned at birth and what they do and do not mean.
• Milestones after a birth injury: what to watch for after the NICU, and how to get a free developmental evaluation.

Sources

This glossary is for general education and is not medical advice. Definitions are simplified for parents; always rely on your child’s care team for information specific to your baby. Reviewed by Laurence P. Banville, Esq. and Max Morgan, Esq. on July 21, 2026.