Micro Preemie Survival Rates and Health Concerns

A micro preemie is a newborn who is very small and born very early. Micro preemie is sometimes defined as an infant born weighing less than 750 grams or before 26 weeks gestation, but experts use overlapping definitions and terms to describe these very premature babies. Micro preemies may also be described as very low birth weight babies or extremely preterm babies.

Since micro preemies are born months before their due dates, they face long stays in the neonatal intensive care unit (NICU). Although many extremely premature babies grow up with no long-term effects of premature birth, some face severe health problems throughout life. Here's what expecting parents should know about micro preemies and extreme prematurity.

Adult hand gently stroking a mico preemie in an incubator — Science Photo Library / Brand X Pictures / Getty Images

Preemies vs. Micro Preemies

Any baby who is born before 37 weeks gestation is considered premature (also known as preterm or colloquially as a "preemie"). The World Health Organization (WHO) defines prematurity based on when a baby is born. Babies born before 28 weeks are considered "extremely preterm." Those born between 28 and 32 weeks are considered "very preterm." Babies are considered "moderate preterm" to "late preterm" if they are born between 32 and 37 weeks.

Micro preemies are the most premature babies of all, born on or before 26 weeks. Many people are surprised by how small micro preemies are. Their skin is thin with visible veins and may look sticky or gelatinous.

What To Expect With a Micro Preemie in the NICU

If you are visiting a micro preemie in the NICU, you can expect to see the following:

Respiratory support: Micro preemies usually have endotracheal (ET) tubes coming from their mouths. The tube is attached to a ventilator that helps the baby breathe. Some micro preemies can breathe on their own and will be on continuous positive airway pressure (CPAP) instead. These babies will have CPAP masks strapped over their noses.
Intravenous lines (IVs): If a micro preemie's digestive system is too immature to absorb nutrition, they will be fed intravenously. Most will have lines in their umbilical cord stumps (called umbilical lines) for the first week or two of life and a PICC line or peripheral IV later.
Monitoring equipment: All NICU babies are closely monitored. Micro preemies may have wired stickers on their chests, feet, wrists, arms, and legs. These are used to check blood pressure, breathing rates, and oxygen levels in the blood.
NG/OG tube: Because micro preemies are too immature to eat from a bottle or from the breast, a tube will go from their mouths (OG tube) or noses (NG tube) into the stomach.

When a baby is born very prematurely, they are at risk for a number of health conditions. Some are short-term, while others may impact them for the rest of their lives.

Short-Term Health Concerns for Micro Preemies

Immediately after birth and during a micro preemie's NICU stay, doctors and nurses watch closely for several serious medical conditions, such as the following.

Intraventricular hemorrhage (IVH)

Intraventricular hemorrhage (IVH) is bleeding into parts of the brain. Micro preemies have fragile blood vessels in their brains, and these vessels can rupture easily. About a quarter of micro preemies have serious IVH. Most cases of IVH resolve on their own, but some babies may need surgery to help drain the extra fluid.

Necrotizing enterocolitis (NEC)

Since micro preemies have immature digestive systems, their intestines are susceptible to infection. With necrotizing enterocolitis (NEC), the linings of the bowels become infected and begin to die. In micro preemies, the condition can be extremely serious. NEC is treated with IV fluids and medication. Surgery may be required.

Patent ductus arteriosus (PDA)

A patent ductus arteriosus (PDA) is a persistent connection between the large blood vessels near the heart. The connection is normal for a fetus but should close when a baby is born and begins to breathe. PDAs are treated with medication or surgery.

Respiratory distress syndrome (RDS)

Most micro preemies have difficulty breathing after birth. This syndrome is treated with respiratory support and medication.

Retinopathy of prematurity (ROP)

The blood vessels in a micro preemie's eyes are not fully formed at birth. When the vessels develop, they may grow so rapidly that they damage the retina. While some cases of retinopathy of prematurity resolve on their own, surgery may be required in severe cases.

Sepsis

Premature babies are prone to infection for several reasons. Micro preemies have immature immune systems and face many invasive procedures in the NICU, each of which can allow bacteria to enter the body, which can cause infection and sepsis.

Long-Term Health Concerns for Micro Preemies

Many micro preemies show no long-term effects of prematurity. However, other micro preemies may have lifelong health issues.

Cerebral palsy: A portion of micro preemies have moderate to severe cerebral palsy.
Chronic lung disease: Many micro preemies need oxygen at NICU discharge. Micro preemies may also have asthma or other respiratory problems, including bronchopulmonary dysplasia (BPD).
Cognitive problems: Developmental delays, trouble in school, and other cognitive problems are common effects of prematurity.
Digestive problems: Micro preemies are prone to digestive problems such as gastroesophageal reflux disease (GERD), food refusal, or poor feeding.
Vision or hearing loss: A small percentage of micro preemies have permanent vision or hearing problems due to complications of prematurity.

Survival Rates for Micro Preemies

Micro preemies are very fragile, and every day that they can spend inside the uterus increases their chance of survival after birth.

Birth Week	Average Survival Rate
22 weeks	About 10% of babies survive
23 weeks	50% to 66% of babies survive
24 weeks	66% to 80% of babies survive
25 weeks	75% to 85% of babies survive
26 weeks	More than 90% of babies survive

How To Improve Your Baby's Chances

Although micro preemies face serious health problems, there are many things that you can do as a parent to give your baby the best possible start:

Get early prenatal care: When you become pregnant, talk to your health care provider about how to minimize your risk of premature birth. Early prenatal care can help you avoid early delivery.
Deliver your baby in a hospital with a NICU: If you know that your baby will be premature, delivering in a hospital with a level 3 NICU with 24-hour neonatology coverage can give your baby the best possible medical support.
Learn the signs of preterm labor: While you're pregnant, make sure that you understand the signs of preterm labor, and seek medical care immediately if you develop any of them.
Seek early intervention: Babies born early may qualify for state-run early intervention programs. Starting these programs as soon as possible can help minimize any cognitive effects of prematurity.

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Sources

Parents uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Extremely Low Birth Weight NICU Graduate Supplement to the Critical Elements of Care for the Low Birth Weight Neonatal Intensive Care Graduate (CEC-LBW). University of Washington. 2004
Preterm Birth. World Health Organization. 2023.
When Your Baby's in the NICU. Nemours KidsHealth. 2019.
Intraventricular Hemorrhage in Babies. Stanford Medicine. n.d.
Necrotizing Enterocolitis. Nemours KidsHealth. 2023.
Retinopathy of Prematurity. National Eye Institute, National Institutes of Health. 2023.
Sepsis and Children. Sepsis Alliance. 2024.
Trends in the prevalence of cerebral palsy among very preterm infants (<31 weeks’ gestational age). Paediatrics & Child Health. 2014.
Cognitive, motor, behavioural and academic performances of children born preterm: a meta-analysis and systematic review involving 64 061 children. BJOG. 2018.

What Expecting Parents Should Know About Micro Preemies