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Environmental Public Health Tracking: Premature Birth Data

Reproduction is complex, and many factors affect parents’ ability to make a baby, carry the baby to term, and deliver the baby without complications. These factors include age, genetics, income/education level, and many others

Premature birth is one type of reproductive outcome. Review the FAQs below for more information about premature birth.

Access birth outcomes data

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A baby is considered to be premature if it is born before completing 37 weeks of gestation. A baby is considered very premature if it is born before completing 32 weeks of gestation. 

There are some risk factors that may increase the chances a baby will be born premature:

  • Carrying more than one baby (twins, triplets, etc.)
  • Having a previous baby born premature
  • Problems with the uterus or cervix
  • Chronic health problems in the mother, like diabetes, obesity, high blood pressure, etc.
  • Certain infections during pregnancy
  • Tobacco, alcohol, or drug use during pregnancy

There are more risk factors that have been linked to prematurity, but the scientific evidence supporting these links is unclear. They include:

  • Late or no prenatal care
  • Domestic violence
  • Lack of social support (friends, family, etc.)
  • Stress
  • Long working hours with long periods of standing
  • Being underweight or overweight before pregnancy
  • Being unmarried
  • Spacing of births (less than 6-9 months between birth and next pregnancy)
  • Exposure to environmental chemicals, such as air pollution and drinking water contaminated with lead

Premature births can happen to anyone and many women who have a premature birth have no known risk factors. Women have the best chance of preventing premature birth by being healthy before and during pregnancy.  Women should also receive quality prenatal care. The Centers for Disease Control and Prevention has more information about preventing premature births on their premature birth page.

Singleton births are births where only one child is born, not twins, triplets, etc. When researchers want to study a specific link, they do their best to eliminate confounding variables, or things that would interfere with studying that specific link.  We want to study how environmental exposures are related to premature births, so we try to remove factors that would influence a premature birth.

Since it has been established by prior research that multiple births (twins, triplets, etc.) are a risk factor for premature births, we have not included them in our premature birth data.
The premature measures using single births are:

  • Percent of preterm births among singleton live born infants
  • Incidence of preterm births among singleton live born infants
  • Incidence of very low birth weight births among singleton born births

Research has shown a relationship between premature birth and exposure during pregnancy to tobacco smoke, air pollution, lead, and some solvents. More research is needed to better understand the relationship.

Last revised August 1, 2022