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What Is a Micro Preemie?


Updated May 16, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Premature baby.
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Question: What Is a Micro Preemie?

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

Babies born after 26 weeks are called very premature, moderately preterm, or late preterm babies.

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.

  • Born at 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: Over 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:

  • Respiratory support: Micro preemies usually have a tube coming from their mouth, which is connected to a ventilator that breathes for the baby. Some can breathe on their own and will be on CPAP instead. These babies will have a CPAP mask strapped firmly over the nose.
  • IV lines: Micro preemies have immature digestive systems and are given IV nutrition at first. Most will have IV lines in their umbilical cord stump (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 chest, feet, wrists, arms, and legs. These measure the baby's heart and breathing rates and his blood's oxygen saturation. A monitor attached to an umbilical artery IV line may measure blood pressure.
  • NG/OG tube: Because micro preemies are 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 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.
  • Respiratory distress syndrome (RDS): Most micro preemies (about 85%) have difficulty breathing after birth. RDS is treated with respiratory support and medication.
  • Patent ductus arteriosus (PDA): Just over half of micro preemies have a PDA. A PDA is a persistent connection between the large 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 into 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): Because 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:

  • Cognitive problems: Developmental delay, 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 parents can do to give their baby the best possible start.

  • Get early prenatal care: 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 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 the best possible start.
  • Learn the signs of preterm labor: Learn 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 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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