What Is a Micro Preemie? - Extremely Premature Babies

Premature baby.
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A micro preemie is a baby who is born weighing less than 1 pound, 12 ounces (800 grams) or before 26 weeks gestation. Since these types of babies are born months before their due dates, micro preemies face long stays in the neonatal intensive care unit (NICU). Although many extremely premature babies grow up with no long-term effects of prematurity, others face severe health problems throughout life.

What Constitutes a Premature Baby?

To give you some context, any baby who is born before 37 weeks gestation is considered to be premature (also known as preterm). Micro preemies are the most premature babies of all. Babies who are born between 27 weeks and 30 weeks gestation are called "very premature," babies who are born between 31 and 34 weeks gestation are labeled "moderately premature," and ones who are born between 34 and 37 weeks gestation are named "late preterm."  

What Is the Survival Rate for Micro Preemies?

Micro preemies are very fragile, and every day that a mom spends pregnant increases her baby's chance of survival.

Birth WeekAverage Survival Rate
22 weeksAbout 10% of babies survive
23 weeks50% to 66% of babies survive
24 weeks66% to 80% of babies survive
25 weeks75% to 85% of babies survive
26 weeksMore than 90% of babies survive

What Does a Micro Preemie Look Like?

Many people are surprised by how small micro preemies are.

Their skin is thin, with visible veins, and it may look sticky or gelatinous. If you are visiting a micro preemie in the NICU, you can expect to see the following:

  • Respiratory support: A micro preemie usually has a tube coming from his or her mouth, which is connected to a ventilator that breathes for the baby. 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 firmly over their noses.
  • IV lines: Micro preemies have immature digestive systems and are given intravenous (IV) nutrition at first. Most will have IV 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 patients are closely monitored. A micro preemie may have wired stickers on his or her chest, feet, wrists, arms, and legs. These measure the baby's heart and breathing rates and his or her blood's oxygen saturation. A monitor attached to an umbilical artery IV line may measure blood pressure.
  • NG/OG tube: Because a micro preemie is too immature to eat from a bottle or from the breast, a tube will go from his or her mouth (OG tube) or nose (NG tube) into the stomach.

Immediate, 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 these, below.

  • Patent ductus arteriosus (PDA): Just over half of micro preemies have a PDA. A 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.
  • 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. About 40% of micro preemies need antibiotics to treat bacterial infections.
  • Intraventricular hemorrhage (IVH): 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.
  • 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. Just under 15% of micro preemies develop ROP, which usually resolves on its own. Surgery may be required in severe cases.
  • Necrotizing Enterocolitis (NEC): Since micro preemies have immature digestive systems, their intestines are susceptible to infection. In NEC, the linings of the bowels become infected and begin to die. About 7% of micro preemies develop NEC, which can be extremely serious. NEC is treated with IV fluids and medication. Surgery may be required.

Long-Term Health Problems of Micro Preemies

Many micro preemies show no long-term effects of prematurity. In fact, by age 8, about 60% have normal IQs. However, other micro preemies may have lifelong health issues, including the ones listed below.

  • Cognitive problems: Developmental delays, trouble in school, and other cognitive problems are common effects of prematurity. About 20% of micro preemies have severe cognitive disabilities by age 8, and another 20% have mild to moderate cognitive problems.
  • Cerebral palsy: About 10% of micro preemies have moderate to severe cerebral palsy.
  • Chronic lung disease: About half of micro preemies need oxygen at NICU discharge. Micro preemies may also have asthma or other respiratory problems, including bronchopulmonary dysplasia, or BPD.
  • Digestive problems: Micro preemies are prone to digestive problems such as GERD, food refusal, or poor feeding.
  • Vision or hearing loss: Between 2% and 3% of micro preemies have permanent vision or hearing problems due to complications of prematurity.

Improving Your Baby's Outcome

Although micro preemies may 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 doctor early about how to minimize your risk of premature birth. Early prenatal care can help moms avoid an early delivery.
  • Have 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 him or her the best possible start.
  • 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.


Hoekstra, R et al. "Survival and Long-Term Neurodevelopmental Outcome of Extremely Premature Infants Born at 23-26 Weeks' Gestational Age at a Tertiary Center." Pediatrics Jan 2004; 113, c1-c7.

Qiu, X et al. "Comparison of Singleton and Multiple-Birth Outcomes of Infants Born at or Before 32 Weeks of Gestation." Obstetrics & Gynecology Feb 2008; 111, 365-371.

Vohr, B et al. "Neurodevelopmental Outcomes of Extremely Low Birth Weight Infants <32 Weeks' Gestation Between 1993 and 1998." Pediatrics Sept 2005; 116, 635-643.

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