For this topic, kidsdata.org offers the following measures:

• Percent and number of infants born at low birthweight, by age and race/ethnicity of mother. Low birthweight is defined as babies who are born at less than 2,500 grams (or about 5 lbs, 8 oz).
• Percent and number of infants born at very low birthweight, which is less than 1,500 grams (about 3 lbs, 5 oz).
• Percent and number of infants born preterm, which refers to births before 37 completed weeks of pregnancy. More than two-thirds of low birthweight babies are born preterm (1).

In addition to being at higher risk of death during the first year of life, babies born weighing less than 5.5 pounds are at increased risk of long-term disabilities, including developmental delays, learning disabilities, and autism (1, 2). Cardiac and/or respiratory distress, brain hemorrhaging, and vision impairments are also problems that low birthweight infants may face (3). Women who are more likely to give birth to low birthweight babies include those with low incomes or education, smoking habits, and those under age 17 or over age 35 (1, 3).

Babies born prematurely may face adverse outcomes as low birthweight infants (4). Preterm birth is the leading cause of infant death in the U.S. (5). Some preterm babies require specialized care in a newborn intensive care unit (4). Women who are most likely to give birth preterm include those who have had a previous premature birth, those pregnant with twins, triplets, or more, and those with certain uterine abnormalities. In addition, demographic and behavioral factors can increase the risk of delivering preterm, including low socioeconomic status, being under age 17 or over age 35, receiving inadequate prenatal care, and smoking during pregnancy (6). About 1 in 9 pregnancies in the U.S. result in preterm birth (3).

The percentage of California babies born at low birthweight increased from 6.1% in 1999 to 6.9% in 2005, and has remained fairly steady since then. At the local level, percentages range from 4.9% to 9.8% in 2013 among counties with available data. The state and all but five counties with data in 2013 met the national Healthy People 2020 objective of no more than 7.8% of infants with low birthweight. However, figures vary by demographic group. For example, California mothers age 45 and older consistently have the highest percentages of low birthweight babies (20.4% in 2013), compared to younger mothers. Among California's racial/ethnic groups with available data, African American/Black mothers consistently have the highest percentages of infants at low birthweight (11.7% in 2013).

California babies born at a very low birthweight has remained steady since 1995, hovering between 1.1% and 1.2%. The state and all but two counties with available data in 2013 met the Healthy People 2020 objective of no more than 1.4% of infants with very low birthweight.

In 2013, 8.8% of infants were born preterm, which represents a decline from the high of 11.2% in 2005. At the county-level, figures range from 6.3% to 13.6% of infants born preterm in 2013. Among counties with available data, all but two met the Healthy People 2020 objective of no more than 11.4% of infants born prematurely.

Some of the risk factors for low birthweight and preterm birth can be influenced by public and institutional policy focused on education, prevention, and treatment. These factors include smoking, drinking alcohol, or using illicit substances during pregnancy; being a teenage mother; and being overweight or underweight (1).

According to research and subject experts, policy options that could influence low birthweight and preterm births include:

• Providing access to early and regular high-quality prenatal care, including ensuring that pregnant women get appropriate nutrition and avoid increased risks of delivering early due to overweight and obesity (1, 2)
• Ensuring that health care systems train clinicians on identifying smokers among pregnant women, and that evidence-based tobacco cessation services are available to pregnant women and reimbursed by insurance (1)
• Sustaining adequate funding for universal screening for substance use among pregnant women, and for treatment services specifically designed for pregnant women who use alcohol or illicit drugs (3)
• Addressing depression and depressive symptoms in pregnant women as depression has been found to have an impact on the incidence of preterm labor and low birthweight (4)
• Supporting a comprehensive approach to women’s health (1), including integration of reproductive planning into women’s routine health care by ensuring access to medical and dental services; included in this approach should be a focus on increasing interpregnancy intervals (at least 12 months), recognizing that short intervals are associated with increased risk for preterm birth (5)