Micro Preemies Survival and Health

A micro preemie in the hospital.
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The term micro preemie usually refers to a premature baby who is born at 28 weeks of gestation or less. This is also known as an extremely preterm birth.

The number of micro preemies born each year is relatively small. According to research published in 2016, 28,861 extremely premature babies were born in the United States in 2011. These babies have very high medical care needs. Survival can range from 10% in underdeveloped countries to 90% in developed countries. However, many more micro-preemies are surviving today than ever before due to advances in medical knowledge and technology that can care for them.

Survival rates are very low for babies born at 22 weeks of gestation, but odds improve with each week of gestation.

Micro Preemie Health Problems

Micro preemies face a number of health problems that are addressed in the neonatal intensive care unit (NICU). Generally, the earlier a baby is born, the higher the risk of complications and the longer they will stay in the NICU. Some health complications micro preemies face include:

  • Hyperbilirubinemia: High levels of bilirubin, a compound resulting from the natural breakdown of blood, causing jaundice. Jaundice can cause brain damage if not treated effectively through the use of special lights that help the body eliminate bilirubin.
  • Apnea: Pauses in breathing that cause decreases in heart rate.
  • Anemia: A lower than normal number of red blood cells, which are needed to carry oxygen to the body.
  • Low Blood Pressure: A common complication that may be due to infection, blood loss, fluid loss, or medications administered before delivery.
  • Respiratory Distress Syndrome: Difficulty breathing due to immature lungs that don't produce enough surfactant, a substance that allows the lungs to expand properly.
  • Bronchopulmonary Dysplasia: A common lung problem among premature infants, especially micro preemies, is often successfully treated with medication and oxygen.
  • Infection: All premature infants, and especially micro preemies, are immunocompromised, meaning they are less able to fight off germs that can cause serious illness.
  • Patent Ductus Arteriosus: In micro preemies, the ductus arteriosus (a short blood vessel connecting the main blood vessel supplying the lungs to the aorta) frequently stays open in premature babies. Due to this abnormal opening, excess blood can flow into the lungs, causing breathing difficulties and in some cases heart failure.
  • Retinopathy of Prematurity: Abnormal growth of the blood vessels in an infant's eye can cause damage ranging from mild to severe (blindness).

Although all micro preemies are very underdeveloped at birth and require constant medical care, many grow up with no long-term effects of prematurity.

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4 Sources
Verywell Family 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.
  1. American College of Obstetricians and Gynecologists. Extremely Preterm Birth. Updated August 2019.

  2. Glass HC, Costarino AT, Stayer SA, Brett CM, Cladis F, Davis PJ. Outcomes for extremely premature infantsAnesth Analg. 2015;120(6):1337–1351. doi:10.1213/ANE.0000000000000705

  3. World Health Organization. Born Too Soon: The Global Action Report on Preterm Birth.

  4. March of Dimes. Premature babies.