Preterm birth is defined as a live birth before 37 completed weeks gestation. Some other classifications of preterm births include late preterm (34-36 weeks), moderately preterm (32-36 weeks) and very preterm (<32 weeks). These classifications are useful because they often correspond to clinical characteristics - increasing morbidities or illnesses with decreasing gestational age. Babies born too soon are often born too small. While the causes of preterm birth and low birthweight may be different in some cases, there is significant overlap within these populations of infants.
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In 2021, 1 in 10 babies (10.5% of live births) was born preterm in the United States.
The rate of preterm birth in the United States is highest for black infants (14.4%), followed by American Indian/Alaska Natives (11.8%), Hispanics (10.0%), Whites (9.3%) and Asian/Pacific Islanders (9.0%).
Compared with singleton births (one baby), multiple births in the United States were about 7 times as likely to be preterm in 2021.
Notes: Very preterm is less than 32 weeks.
Sources: National Center for Health Statistics, final natality data. Retrieved June 7, 2023, from www.marchofdimes.org/peristats.
In 2021, 58,258 babies, or 1.6% of live births, were very preterm in the United States.
Major risk factors for preterm and very preterm births include multiple births, history of preterm delivery, stress, infection, smoking and illicit drug use.
Very premature babies who survive may suffer lifelong consequences, including cerebral palsy, blindness and other chronic conditions.