The purpose of this project was to collect information on surviving infants with birth weights of <400 g.


A Web-based registry was started in 2000 after searching for published reports of infants who survived to hospital discharge despite being born at <400 g. Fifteen cases were identified from scientific and lay print and Web-based publications. Parents, patients, and health providers were invited to submit data on additional infants. In the case of submissions from parents or patients, the information was confirmed by communication with a treating physician.


As of September 1, 2010, the Tiniest Babies Registry had compiled data on 110 patients born between 1936 and 2010. The number of infants who survived each year increased since the early 1990s. The infants in the registry weighed between 260 and 397 g at birth and had gestational ages from 2167 to 34 weeks. Eighty-three (75%) of the patients are female. The 10 smallest infants are female, and the registry contains only 1 boy who was born weighing <300 g. The patients were born in 10 countries, including 80 (73%) born in the United States. The information on long-term functional outcome and health outcomes is limited. Many patients have ongoing health and learning concerns, and most of those for whom growth data are available remain short in stature and underweight for their age.


Survival of infants born weighing <400 g is rare but increasing. The Tiniest Babies Registry provides a repository for information about this remarkable group of infants.

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